THE FOUNDATIONS OF
WISDOM

VOLUME 3

PHILOSOPHY OF
MAN

THE FOUNDATIONS OF
WISDOM

VOLUME 3

PHILOSOPHY OF
MAN

FR. SEBASTIAN WALSHE, O. PRAEM.

TAN Books
Gastonia, North Carolina

Foundations of Wisdom: Volume 3: Philosophy of Man © 2023 TAN Books

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GENERAL PREFACE

Hunting for Happiness

The discovery and development of philosophy is part of man’s larger search for happiness. As man was hunting for happiness, he found philosophy. Most of human ingenuity and energy were originally directed toward removing the obstacles to happiness: for example, the arts of hunting and agriculture were developed to alleviate hunger; the art of housebuilding was developed to alleviate the suffering associated with excessive heat and cold; various martial arts and weapons were developed to protect against violence from animals and other men; medicine was developed to cure illness. But once these arts had been developed and man had time for leisure, it became apparent that there exists in man a more fundamental desire than that which is satisfied by food, clothing, and bodily health. It is a desire not merely to avoid evils, but a desire for some positive good, and it is a desire for a positive good which is not merely instrumental to something else (such as practical knowledge), but a good desired for its own sake. Aristotle expressed this desire simply in the statement, “All men by nature desire to know.”

It may seem strange that happiness should have much to do with knowledge. After all, very few men dedicate real effort and time to searching for knowledge. And what knowledge they do search for tends to be practical in nature: that is, it is for the sake of making or doing things. Yet, it is an indisputable fact of history that once the chief practical arts had been established, and the needs of the body provided for, men naturally turned to philosophy in their leisure time. Aristotle recounts that “After all such [practical] arts had been developed, those sciences were pursued which are sought neither for the sake of pleasure nor necessity. This happened in places where men had leisure. Hence the mathematical arts originated in Egypt where the priestly class was permitted leisure.”¹ And again: “When nearly all the things necessary for life, leisure and learning were acquired, this kind of prudence began to be sought.”² But if this is so, how do we account for the fact that so few people consider knowledge to be essential for happiness?

This question is like the question of why so few children prefer a high paying job or an excellent education to ice cream. First of all, since the goods of the body are better known than the goods of the soul, it is natural that men should seek to provide for the goods of the body first. Secondly, happiness is not found in the possession and exercise of just any knowledge, but in the best knowledge. And finding and using this type of knowledge is very difficult to achieve. Just as it would be impossible for a child to perform well at a high paying job or to receive an excellent education all at once, so it would be impossible for someone to acquire and use the knowledge needed for happiness without first passing through years of experience and study. Finally, notice that Aristotle did not say all men naturally desire to come to know, but rather that all men naturally desire to know. Samuel Johnson, encountering a famous landmark in Ireland, once quipped that it was “worth seeing … but not worth going to see.” There is a similar relationship between knowing and coming to know. Coming to know can be arduous and even painful. But if you asked any man on the street whether he would like to know some important truth if it took no effort, I would bet he would say yes. But because many obstacles stand in the way of possessing knowledge, there are few who seek it.

Philosophy is near the end of man’s search for happiness. However, even within philosophy itself there is an order of discovery arising naturally from the search for happiness. For we want to know the supreme good of man—that is, what man has been made for—but to know that we need to know what man is, and since man is a natural being, we need to know what nature is. So philosophers began to examine nature. But once these things had been worked out in outline, it became clear that the nature of man is difficult to know, that it is even difficult to know about the existence and nature of the soul, and that the highest perfection of the human soul, wisdom, is even more difficult to know. Therefore, it was necessary to develop one final art: logic, which assists us in coming to know difficult truths. Plato’s Socrates seems to have been the first to acknowledge a need for an “art about arguments” in the Phaedo, precisely as he is searching to discover the existence and nature of the human soul.

The order of discovery in philosophy is almost opposite to the order in which philosophy should be learned. For students should first study logic, which is the art that treats of acquiring the good of speculative reason: truth. Since every science searches for truth, logic teaches how to proceed correctly in every science. Second, they should study mathematics, which among the sciences is the easiest in which to find certitude (hence there is much agreement in this part of philosophy). Third, they should study natural things (or natural philosophy).³ Fourth, among natural things, they should focus their study upon living things, especially man (the study of the soul). Fifth, once they know accurately the nature of man, and the various powers and perfections of the soul, they should study the good for man (ethics). And since man’s supreme good consists in knowing things better than himself, the philosopher should study the first causes of all being (wisdom or metaphysics) last.⁴ For the very exercise of knowing these things higher than man is the happiness which man desires. That is, natural happiness consists in contemplating the truths which are the conclusions of metaphysics.

Because this is only an introduction to philosophy, this text will not consider the last part of philosophy—that is, metaphysics). Such a consideration belongs not to the beginning student, but to an advanced student. Moreover, because the science of mathematics is widely taught, and much easier than the other parts of philosophy, this text will not consider that part of philosophy either. Perhaps the best elementary treatment of mathematics can be found in Euclid’s Elements.

Finally, this text will not proceed in a primarily historical method, as is typical in most introductions to philosophy. The timeline of the history of philosophy is not necessarily a progression from ignorance to knowledge or error to truth. It is quite possible for an earlier philosopher to know more than a later one, and vice versa. Nor is the order of history necessarily the best order for the beginning student to follow if he is in search of truth. This text does not seek to inform the student about the positions taken by various philosophers, but rather to lay out the method best suited to human nature of coming to understand the order among the ultimate causes of reality. We study the Pythagorean Theorem not to know that Pythagoras thought, but because it is true and worth knowing. And it would be worthwhile to study the same theorem even if it was discovered by Frankie Watkins. In philosophy, we are not so much concerned with who discovered some truth as with the truth itself and the reasons why it can be known. So while much of what is found in this text will be truths discovered by Aristotle and Saint Thomas Aquinas, they stand on their own and do not rely upon the authority of those who first discovered and presented them.

_______________

¹ Metaphysics 981b22-24. Genesis 47:22 provides independent confirmation of the leisure afforded the priestly class in Egypt.

² Metaphysics 982b22-23.

³ The area of study that used to be called natural philosophy was concerned with areas of knowledge we tend, confusingly enough, to lump under the label of “science” today.

⁴ This order of study is laid out by Saint Thomas Aquinas at the beginning of his Commentary on Aristotle’s Nicomachean Ethics and at the beginning of his Commentary on the Book of Causes.

INTRODUCTION

Why Study the Soul?

Knowledge about the soul is one of the best kinds of knowledge a man can have. Some kinds of knowledge are good to have because of their certitude (like mathematics, which is so certain that agreement is common among mathematicians). Other kinds of knowledge are good to have because of their intrinsic nobility (like knowledge about God, which is knowledge about the best thing there is). The knowledge of the soul is both: certain and noble.

Knowledge of the soul is certain because each person has immediate, first-hand, and undeniable experience of his inner life and activities. We are certain that we feel, that we think, that we love. Even if everyone around us told us: “No, you don’t feel sad,” or “No, you don’t like chocolate ice cream,” we would remain completely certain that we do feel a certain way, we do think such and such, we do love this thing. The arguments of others would crumble before our first-hand experience of our own inner life. In fact, our certitude of our inner life and activities is so great that some philosophers, like Descartes, were deceived into thinking that we are more certain that we think than we are certain that we exist! He said, “I think, therefore I am.”⁵ While that is a bad argument, it is nevertheless a good testimony to how certain we are about the inner workings of our life, the activities of our souls.

The soul is also a very noble subject of study. As Jesus once pointed out, “For what will it profit a man, if he gains the whole world and forfeits his life? Or what shall a man give in return for his life?” (Mt 16:26). We value our souls above all physical goods: it seems to be what is most God-like in us, for by it we know and love. Therefore, to come to know something about the soul would be something very worthwhile.

Finally, the study of the soul is something very useful in our pursuit of wisdom because knowledge of the soul assists us in every branch of knowledge, for it is by means of the soul that we know. We sense and understand by means of our soul. Therefore, knowing more about the soul can help us to understand each of the things we know better.

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⁵ Of course, it is fair to ask the question: What does “I” mean in the first premise “I think” if it does not refer to an existing thing? Descartes, it seems, is guilty here of assuming what he is trying to prove.

CHAPTER 1

Where to Begin

How to Begin a Study of the Soul

One of the first difficulties modern students typically have when beginning a study of the soul is that the word “soul” has so many ideas associated with it in the modern mind. To most people, the word “soul” conjures up ideas of ghosts, religion, the afterlife, or even reincarnation. Movies, preachers, and new age books all have something to say about the soul: the soul is what Jesus saves, the life force that continues after death, the divine in us, etc. It can all get very confusing very quickly.

We do not want to dismiss off-hand the various things that people say about the soul, but it is not very helpful to begin with them. One thing is clear: none of these assertions is self-evident to a beginning student. Besides this, many of the things modern people say about the soul are contradictory and mutually exclusive—in other words, only some of these ideas can be true, and it is not immediately clear which are. So we cannot take these ideas and assertions about the soul as our starting point, though perhaps some of them will eventually prove true. And while for those who accept Christian revelation, their faith provides them with a sure guide to truth about the soul, nevertheless, we are approaching the soul here as philosophers, trying to discover what is true about the soul from common experiences that everyone has, regardless of their faith.

So where should we begin? We know from logic that if we are to gain scientific knowledge about the soul, we will have to construct some demonstrations about it, and to do that, we will need a definition of the soul. So we know that much: we need to find a definition of the soul, and preferably an essential definition if such a definition is possible. That narrows down our job: the first thing we are looking for is a definition of “soul.”

But even this seems daunting. How can we find a definition of something so elusive as the soul, something so likely to produce contradictory opinions? One thing I like to point out to students when they are struggling to understand and define a term is that they already have a pretty good idea about what any given word, like the word “soul,” means. If I were to ask each student here to give me a meaningful sentence using the word “soul,” they would probably find it a fairly easy task. Sentences like “I took my soul out for a walk and then gave it a bath” or “my brother is more soul than I am” or “that rock weighs four soul” are easy to identify as incorrect usages of the word “soul.” Therefore, each of you really does have a pretty good idea of what “soul” means and what it doesn’t mean. It’s just a matter of putting your idea into words.

The Nominal Definition of Soul

Typically, the best place to start with a difficult definition is with some kind of nominal definition. From there we can seek an essential definition, or at least a definition by properties. Often, looking at a word’s etymology can help us get a nominal definition.⁶ Greek and Latin are some ancient languages where we first find the word soul used. The Greek word for soul is “psyche” (pronounced: SUU-kay), which just meant “breath,” while the Latin word for soul is “anima,” which means life (we get the English word “animated” from the Latin word “anima”). According to the original usage of the word “soul,” ensouled things are living, breathing things. Now that’s not too hard for us to grasp. Those are things very close to our everyday experience.

Let’s propose our first, nominal definition of soul: soul is whatever makes living things different from non-living things. Now, right away someone will say: but there are lots of differences between living and non-living things, which one should we call the soul? Some living things see, some grow, some think. All of those differences—seeing, growing, thinking, etc.—are different ways of living, but we are not looking for some particular difference. Rather, we are looking for whatever it is that is ultimately responsible for life as such, not just some specific manifestation of life: that’s what we mean by the soul. True, we will eventually want to investigate these different manifestations of life and study whether they are the result of different kinds of souls. But for now, we just want to come to a general concept of soul which includes any form of life. The soul is the very first cause upon which living depends. So, to be clearer, let’s state our nominal definition this way: soul is whatever is ultimately responsible for the difference between living and non-living things. Or we could put this even more simply by saying: the soul is the first principle of life in a living thing.

According to this first, nominal definition of soul, whatever is alive can be seen to have a soul: men, birds, carrots. Yes, you read that correctly: carrots. Usually, at this point in the class, my students and I engage in a dialogue that goes something like this:

Joe Student: Carrots?! You mean to tell me that carrots have a soul? That’s crazy talk. Do you expect me to believe that there’s an afterlife for carrots?

Fr. Sebastian: No, I don’t expect you to believe anything of the sort. Remember, I told you before, throw out all those ideas that come with the modern mindset about the soul. When I say something has a soul, I am making a very limited claim: that it’s alive. I am not making any claims about its condition after death, and we are in no position to assert that a soul can exist apart from the body.

Joe Student: But if carrots have souls, doesn’t that make them just like men?

Fr. Sebastian: No, not just like men. There may be different kinds of souls. Human souls would presumably be different from carrot souls. But it is true that if carrots have souls and men also have souls, they have to be like men in some way. First of all, both have to be alive. And in fact they do share some kinds of living activities, like growth and receiving nourishment.

Joe Student: But why should I believe that things like growth and taking in nutrition are caused by something immaterial like the soul. Couldn’t those things be explained without bringing in the immaterial?

Fr. Sebastian: Don’t worry. I’m not saying at this point that the soul is even something immaterial. If this turns out to be the case, we will have to prove it. As far as we’re concerned, whatever makes a carrot alive may well be just some material or mechanistic cause. I’m not asking you to assent to anything other than the fact that carrots are alive: that they grow, take in nourishment and reproduce, and therefore, they must have some principle within them that makes them different from things that are not alive.

Joe Student: Oh, OK.

Now that we’ve cleared that up, one thing that emerges is that the soul is something very natural, very commonplace, not some strange transcendent being that belongs to the world of ghosts and the supernatural and the paranormal. The soul is as natural as life itself.

The Place of the Study of the Soul in the Whole Body of Knowledge

Now is a good time to determine where the study of the soul fits in with other things that we can know. Let’s look back at our “road-map of all things knowable.”⁷ Recall that everything that can be known has an order, and order is related to our reason in three ways: there is the order discovered in things by our reason; the order put into things by our reason; and the order revealed to reason by God. Now, certainly there are things revealed by God about the human soul, but that is the province of theology, and we are doing philosophy here. Thus, we are not talking about an order revealed to reason. Neither is the study of the soul found in the order put into things by reason. The soul is what makes living things to be alive, and it is clear that living things are not the product of human reason: living things come about by nature, not by human art. In fact, most living things existed long before men existed. That means the study of the soul falls under the order discovered by reason in things—that is, the study of the soul falls under one of the speculative sciences. Recall again that this order discovered by reason can be about things which exist in matter and are defined with matter (natural philosophy); things which exist in matter but are defined without matter (mathematics); and things that do not exist in matter and are not defined with matter (metaphysics). Into which branch does the study of the soul fall? Well, we seem to be pretty sure that the soul is not studied in mathematics: mathematical things like lines and numbers do not make something alive. We are also sure that the living things with which we are most familiar are material things, like men and dogs and trees. So the soul seems to be something which exists in matter rather than something that exists without matter. As such, the soul should be studied as a part of natural philosophy.⁸ We can make another argument that comes to the same conclusion: it belongs to the same science to study its subject and the principles of its subject. For example, it belongs to the same science to study numbers and the principle of numbers (i.e., the unit); and it belongs to the same science to study lines and points (since a point is a principle of a line). But the soul is a principle of a living thing, and living things are clearly natural things. So the soul should be studied in natural philosophy. Is the study of the soul the same as natural philosophy? That can’t be since living things are not the only natural things: rocks are natural, as are the elements and various compounds. So the study of the soul will only be a part of natural philosophy. But which part? How should we divide up natural philosophy to identify which part the study of the soul belongs to? Since natural philosophy has mobile being as its proper subject, then the per se divisions of natural philosophy will follow the per se divisions of motion. Recall that there are three kinds, or species, of motion: local motion (change of where), alteration (change of quality), and growth (change of quantity). Which motion is most characteristic of all living things? Growth. All living things grow, usually becoming thousands or millions of times bigger than they start out. In fact, in the natural world, it is hard to find things which grow that aren’t living. Therefore, the soul is studied in the part of natural philosophy which is about growth. If we look at the modern sciences, we see that biology (in which we study living things and the principle of living things, the soul) corresponds to natural things which have an intrinsic principle of growth, while physics is the study of natural bodies insofar as they move by local motion, and chemistry is the study of natural bodies insofar as they undergo alteration. The Figure 1 on the next page will aid us in remembering the divisions we have covered:

Figure 1

Summary

• Generally understood, the soul is the first principle of life in a living thing.

• Studying the soul falls under the domain of natural philosophy.

• Within natural philosophy, studying the soul falls under the type of motion associated with change in quantity: growth.

• The study of motion as growth corresponds to biology, the study of living things and the principle of living things.

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⁶ The etymology of a word is the history of its usage from the first times and languages in which it was used. (This should not be confused with entomology, the study of insects).

⁷ As first found in Volume I: Logic, chapter 3.

⁸ Someone could object right now and say: but the soul is immaterial, it doesn’t exist in matter, so it should be studied in metaphysics, not natural philosophy. That is a serious objection which we will have to answer more fully later, but what is clear enough now is that even if it turns out that some kinds of souls, like the human soul, can exist apart from matter, they never come into existence without matter. Not only that, but it is not even obvious at first if the human soul or any other kind of soul can exist without matter. Yet it is obvious that human beings and other living things are material. That is enough evidence to start off with the assumption that the soul ought to be studied in natural philosophy. Nevertheless, we will have to return to this problem later once we have examined the nature of the soul in greater depth.

CHAPTER 2

From a Nominal to an Essential
Definition of the Soul

Now that we have considered some good reasons why we should study the soul and where the study of the soul belongs in relation to the other arts and sciences, our next job is to find a more perfect definition of soul. This is not going to be easy, and we will have to make use of many of the tools we have acquired from logic and much of what we have learned about natural things from natural philosophy.

Usually, we know what a name means before we know whether or not there is something in reality corresponding to that name. For example, we know what the name mermaid means (half-woman, half-fish), and we know what the name God means (the supreme being and governor of the universe) before we know whether or not something exists corresponding to those names. Similarly, we know what the name soul means before we know if there is something in reality corresponding to the name soul. And we already gave such a definition of the name “soul” in the last chapter: soul is whatever is ultimately responsible for the difference between living and non-living things; or alternatively: the soul is the first principle of life in a living thing.

Our first task is to determine whether or not there is some real being that corresponds to our nominal definition. It is obvious to everyone that there is some real difference between living and non-living things. Why would we call something NON-living if we didn’t notice a difference between it and something living? Living and non-living are opposites. How could there be no difference between opposites? Sure, this difference might turn out to be something material, like the DNA (Deoxyribonucleic acid) found in all living things, but there must be some real difference (for example, to have DNA is really different from not having DNA). And, therefore, there must also be something which is ultimately responsible for this difference. So right away we can see that there is some being which corresponds to our nominal definition of soul.

Since the soul exists, we can give something more than a nominal definition of the soul. And since the genus of any definition is what is better known to us than the definition itself, we should first look for the genus in the definition of soul. Here is where our study of the ten categories becomes especially helpful. Everything which exists is either a substance or one of the nine accidents (quantity, quality, etc.). So within which category can we place the soul? I think it is easier to begin by ruling out certain categories first: the soul is very obviously not a where or a when. Nor is the soul a position or an outfit. We don’t speak about the soul as if it were an acting upon or an undergoing. Examples of things in the category of acting upon are cutting, burning, hitting, etc. But we do not speak about soul that way; nor do we speak about it as if it were an undergoing like being cut, being burnt, being hit, etc. The soul does not seem to be a quantity either, since it in no way answers the question “how much?” or “how many?” So that leaves three categories:

1. substance,

2. quality, and

3. things said relatively (toward another).

Let’s look at some reasons why the soul might or might not be in each category. At first, the soul seems to be something relative toward another: I say “up,” you say “down;” I say “husband,” you say “wife;” I say “soul,” you say…“body.” Since the soul is the soul of a body, it seems to be relative to the body. Besides, life is found in things which have the right proportion of elements and compounds, so the cause of life seems to be some kind of proportion or harmony, and proportion is a kind of relation. Furthermore, the soul is what unites the diverse members of a body into a single organism. But unity is also a kind of relation, so it seems that the soul is a relation of some kind.

On the other hand, the soul seems to be a quality. For qualities are present in a subject in such a way as to make that subject to be of one kind rather than another. The soul seems to be present in the body, making it a living kind of thing. Besides, one quality is similar to or dissimilar from another, but we say that one soul is similar to another soul, as a zebra soul is similar to a horse soul, but dissimilar from a turtle soul. Or again, we say that one man’s soul is similar to another man’s soul.

But the soul also seems to be a substance, since a substance exists by itself and is the subject of accidents. Now the soul seems to be the subject of accidents like habits and activities. And in the opinion of some, the soul is able to exist by itself. Moreover, the mark most proper to substance is that substance is able to receive contrary attributes while remaining one in number, and this seems to be true about the soul, which can receive contraries like virtue and vice, knowledge and error, while remaining the same individual soul.

On the other hand, the soul does not seem to possess all the marks of substance. Remember that there were six marks of substance Aristotle gave in the categories to help us identify the category in which to place a given name or thing (for example, a substance does not allow of more or less, a substance does not have a contrary, etc.). One of those six marks was that a substance is a “this something,” a concrete being complete in its nature. But a soul does not seem to be such a thing. So there are also difficulties with saying that a soul is a substance.

As we can see, there are reasons for placing the soul in each of these three categories. Aristotle observed that it is the mark of a good definition that it resolves the difficulties surrounding the thing which is defined, for a good definition not only matches our experience of a thing, but it also reveals why there should be difficulties about it in the first place. So if we define soul well, we will see why it is that a soul seems in some way to be in all three of these categories.

To identify the genus of soul more precisely, we need to reflect more carefully upon our experience of life. Recall that the soul is the first principle of life in a living thing. If the soul is an accident like relation or quality, then life should be something accidental to the thing in which it is. But, in fact, our experience tells us the opposite. For living things, to live is to exist. If I say that Socrates no longer is, or no longer exists, this means he’s dead. It’s quite different from saying Socrates no longer is overweight or sitting: life is not like a mere accident such as being overweight or sitting. Similarly, it makes sense to talk about a short horse or a tall horse, a brown horse or a white horse, a sick horse or a healthy horse. But when I talk about a live horse and a dead horse it’s not the same: a dead horse isn’t a horse at all. Being alive isn’t accidental: a horse can’t lose its soul and remain a horse. That is certain evidence that the soul bears on the very essence of a living thing: the soul makes a living thing to be what it is. So the soul is something substantial, essential, not just accidental.

If the soul is in the category of substance, and since every natural substance is a composite of matter and form,⁹ then it follows that the soul must either be:

1. a composite substance, or

2. the matter of a composite substance, or

3. the form of a composite substance.

And this is an exhaustive division.

Now the soul cannot be matter (2). For if the soul were matter, then every material thing would have a soul and hence would be alive. But it is obvious that not every material thing is alive. Nor can the soul be some body composed of matter and form (1), since the soul is the first principle of life, and since every composite is after the things of which it is composed. Therefore, it must be (3), the form of a composite substance.

Put another way, let’s assume that the soul is some body, like DNA, which is composed of matter and form. Would this DNA (or whatever you claim is the body ultimately responsible for life) be a principle of life simply because it was a body or simply because it has matter, or rather would it be the principle of life insofar as it was a body of a certain kind or matter of a certain kind? Certainly, it is not insofar as DNA is matter or a body that it causes life: for then any body and any material thing would be alive. Therefore, it must be because DNA is a body of a particular kind (e.g., one having a double-helix molecular structure) that causes life. But if this is so, then there must be some principle prior to DNA which makes DNA to be the kind of body it is. And since the soul is the first principle of life, it follows that this prior principle which makes DNA to be what it is would more correctly be called the soul. So the soul would have to be that which makes a living substance to be what it is. And this is just what we mean by substantial form: that which makes a substance to be what it is. So again, we see that the soul must be in the category of substance as a substantial form (3).¹⁰

Furthermore, since every substantial form is the form of some body, it follows that the soul is the form of a body.¹¹ Clearly the soul will not be the substantial form of an artificial body, since an artificial body is what it is based upon some accidental form introduced from outside, while the soul is an intrinsic principle of life. Remember that nature is an intrinsic principle of motion and rest, so that whatever has such an intrinsic principle must be natural. Therefore, the soul will be the form of a natural body. And since the soul is what causes life in that in which it is, this body will necessarily be a living body (which will necessarily be organized). So in summary we can say that the soul is the substantial form of a natural body capable of life, or put more distinctly, the soul is the substantial form of a natural, living body having organs capable of exercising living activities.¹²

Review of the Basic Experiences Presupposed to Defining Soul

Our definition of soul ultimately rests upon a handful of very certain, very basic experiences. Here it will be helpful simply to lay these experiences out explicitly in order so that the student can see how certain this definition of soul is. Remember that whenever we start with the meaning of a name, a nominal definition, we need to consult experience, the real world, before we can say for certain that there is some reality corresponding to our nominal definition. At each point where we refined our definition of soul, we looked back at experience to see if the more refined definition corresponded to something real (remember that one of the marks of a good definition is that it must correspond to an existing thing). The following table lays out each stage in formulating the essential definition of soul. In the left column are placed the various definitions of soul, which become more precise the farther down the chart you go. In the right column are placed the experiences which justify refining the definition.

All four of these experiences are very certain: it’s hard to imagine someone asserting that there is absolutely no difference between living and non-living things, or that a dead horse is just as much a horse as a living horse. Moreover, to admit these experiences is to admit that the soul is a substantial form. Once we have seen based upon these experiences that the soul is a substantial form, it is very simple to complete the definition: all we have to do is say what the proper subject of this substantial form is. It is clearly a kind of body (all living things have bodies). And it is clearly a natural body (all living things are natural, since they have an intrinsic principle of motion and living activities). And, upon investigation, experience teaches that all living things have bodies with organs that perform living activities (since they need to do things like acquire and digest food, etc.). So we have arrived at our complete definition of soul: the substantial form of a natural living body having organs capable of exercising living activities.

Have We Defined Soul Well?

As I mentioned earlier, coming to a definition of soul was not easy. And, as Aristotle said, if we have defined something well, not only will it fit with our experiences, but it will resolve the difficulties around the thing defined and will even manifest why there were difficulties in the first place. So let’s check to see if we have in fact come to a good definition of soul. In our course on logic, we identified four marks of a good, essential definition:

1. the definition should correspond to an existing thing;

2. the definition should be coextensive with the thing defined;

3. the defining terms should be better known than the term defined; and

4. the definition should give an account of the causes of the thing defined.

First of all, it is clear enough that our definition corresponds to an existing thing. That was the point of checking with our experience each time we refined the definition. It is clear that there is a difference between living and non-living things. It is also clear that living things are substances and since all substances have a substantial form, there must exist substantial forms of living things. So our definition corresponds to something in reality.

But is our definition of soul coextensive with the thing defined? Put another way: is our definition too big (containing something that isn’t a soul) or too small (not containing everything that is a soul)? Looking back at this definition we notice something interesting about it: the definition seems to include things in it that are not the soul. For example, the definition of soul includes “body,” which is not what a soul is. At first this may seem to be an incorrect way of defining. If the definition we have given includes something which is not what a soul is, haven’t we made our definition too big, like a man who builds a fence that includes some of his neighbor’s property?

To answer this difficulty, it is necessary to recall another distinction we made in the part of logic about definitions: the distinction between definitions of complete things and definitions of incomplete things. A complete thing stands on its own and needs nothing else to support it. For example, a man is defined as a rational animal. Rational and animal are both what a man is: what is a man? An animal. In what way is man an animal? In a rational way. So in complete things, like a man, or any complete substance, the definition needs nothing from outside what the thing is to complete or support it. On the other hand, there are incomplete things that do not stand on their own. If I were to define “snub,” it would be defined as a certain curvature of a nose (someone with a snub nose has a nose which is somewhat turned up, a little like a pig’s snout). Here snub does not stand on its own: it is a curvature, but it is in a nose. Similarly, if I were to define color, I would have to include the fact that it is in a surface. Color is essentially a quality, but it is always a quality of a surface or in a surface. The proper subject of color is surface just as the proper subject of snub is nose. So with incomplete things, since reason sees that they do not stand on their own, we have to include their proper subject or matter in their definition. This proper subject is not so much what the thing is, but rather what it is in or of.

For this reason, the proper subject is distinguished from the essence of the thing. Here in the case of the soul, the essence of the soul is expressed by the words “substantial form” while the proper subject of the soul is expressed by the words “natural, living body.” If someone were to ask me: what is a soul? I would say, it is a substantial form. But if they were to ask me further: what is a soul in? I would answer, it is in a natural, living body. Both are necessary to fully understand the soul. So it turns out that our definition isn’t too big after all, since we are not saying that a natural, living body is what the soul is, but rather, we are indicating the proper subject of the soul, which is still necessary for our complete understanding of soul. Thus, our definition is coextensive with the thing defined.

Does our definition use terms better known than the terms defined? Here again, it seems that it does not. For everyone has heard the word soul and has a basic idea of what it means, but who ever heard of the expression “substantial form” before taking a philosophy class? It’s important to distinguish between words that are commonly used and words that signify things that are well known. The Hawaiian language does not have a verb to signify being or existence. Is this because existence is not well known? To the contrary, it is so well known that we tend to overlook it, like the air we breathe, or other aspects of our experience which are so common that we rarely distinguish them from other things. In a word, well known things often go unnamed. Indeed, substantial forms are in everything we experience. We know this very well from the fact that there are different substances which can change into one another (like the cow that eats grass). If the matter of different substances is the same, but the substances themselves are different, then whatever it is that makes one natural substance different from another is all we mean by substantial form. That’s something very basic to our experience: there is something that makes substances different from each other.

So while the expression “substantial form” is not a commonly used expression, still it signifies something very well known to us. Indeed, it is better known than the term “soul” since it is a more universal concept than soul: for just as living things are particular kinds of natural things, so soul is a particular kind of substantial form (the substantial form of a living thing). A substantial form is whatever makes natural substances different from each other, so a particular instance of this is the soul which is what makes living things (a particular kind of natural substance) different from each other. In a similar way, substance is better known than man, since man is a particular kind of substance (though we probably used the word “man” before we ever heard of the word “substance”).

Finally, does our definition of soul give an account of the causes of the thing defined? Certainly, the formal cause is expressed by the phrase “substantial form.” We also give something like a material cause in our definition, since we express the proper subject or matter of the soul by the phrase “natural, living body.” What we are missing, however, is the agent and the final cause. That’s OK for now, since we have both the intrinsic causes (form and matter), but if we are to come to a more perfect understanding of soul, we will have to find out what the agent and final cause of the soul is. It turns out that we will complete this task in ethics (next quarter) when we determine the nature of happiness.

So our definition of the soul seems to satisfy the four marks of a good definition. One task remains before us: does this definition of the soul resolve the difficulties and show why there were difficulties to begin with? Remember that there were difficulties about whether the soul belongs in the category of substance or whether the soul is properly an accident, such as quality or relation. Looking at the definition of the soul again—the substantial form of a natural, living body—we can see right away why these difficulties came up. First of all, the soul does not fit perfectly into the category of substance since it is not a complete being, but rather it is a part or a principle of a complete substance. Hence, of the six marks of substance, the mark that a substance is a “this something,” a concrete being complete in its nature, does not fully apply to soul. Something similar might be said of a point. A point is not exactly a quantity in the fullest sense of the word, but it is a principle of a line which is a quantity in the fullest sense of the word.

We can also see from this why it looks at first as if soul belongs in the category of relation (toward another). For the soul is by nature a part, and every part is related to some whole or another part of that whole. Similarly, a head is a head of a body, even though it is clearly a substance. So we speak about the soul as if it were relative to another thing, but here we would be talking about something relative according to the way we speak (secundum dici) not relative in its very being (secundum esse).

Finally, we can see why the soul might appear to be in the category of quality. For a soul is a form, and every form makes a thing to be the kind of thing it is. Qualities also indicate how things differ in kind, but only in an accidental way, not in a substantial way. If I asked you: what kind of horse is that? You could answer: a brown horse or a racing horse. Being brown and having the ability to race are both accidental qualities (from the third and second species of quality, respectively). For this reason a brown horse or a racing horse is just as much a horse as a white horse or a non-racing horse. But it is different with a living horse as opposed to a dead horse. Some forms make a thing to be what it is simply speaking (substantial forms) while other forms make a thing to be what it is in some respect (accidental forms, especially qualities).

So our definition of a soul satisfactorily resolves all those difficulties we had when we first tried to define it. That is a very good sign that we have hit upon the correct definition of soul.

Two Corollaries Following from the Definition of Soul

From the above definition of soul, two important corollaries follow. First, the statement that soul and body are one is a self-evident statement. It is only when the soul is conceived as a separate, complete substance, independent of the body, that a problem arises about how the soul and the body are united.¹⁴ In fact, the soul stands to the body as its form, not as a different substance from the body: the soul is in act what the body is in potency: they are the same substance but related as the act and ability of that same substance. And just as it is obvious that the shape of a marble statue is together with the marble, so for the same reason it is obvious that the form of the body is together with the body. To be more precise, the statement that the soul is one with the body (like the statement that the shape of marble is together with the marble) is a per se 3¹⁵ self-evident statement.¹⁶ That is, the predicate belongs to the subject as to its immediate cause.

The second corollary that follows from the definition of soul is that the soul moves the body as a form, not as an independent agent. Thus, the soul is not related to the body as a driver to a car or a captain to a ship. A driver and a captain are independent substances that move their vehicles as agent causes. The soul makes the body to be what it is, which is not true about a driver or a captain. One driver can get out of a car, and another get in without at all affecting what the car is. But if the soul leaves the body, the body ceases to be what it is. This also raises some interesting questions about the possibility of reincarnation, but we will have to consider that question at the appropriate place below when we consider the immortality of the human soul.

Summary

• The nominal definition of soul is “the first principle of life in a living thing.”

• The essential definition of soul is “the substantial form of a natural, living body having organs capable of exercising living activities.”

• We arrive at the essential definition of the soul from the nominal definition of the soul based upon obvious, common experiences.

• It is self-evident (per se 3 [the predicate belongs to the subject as to its proper cause]) that the soul and body are one.

• The soul and body are not related as driver to car, since the soul makes the body to be what it is.

_______________

⁹ Recall that this was proved in natural philosophy where our analysis of substantial form revealed that every natural substance is a composite of prime matter and substantial form.

¹⁰ Supplementary text: Summa Theologiae, Ia, q.75, a.1.

¹¹ Recall that we are considering form in the context of natural philosophy, so that form is understood here as a form in or of matter. The word “form” later gets extended to refer even to immaterial substances, but that is not the sense of form being used here.

¹² Supplementary text: R. McInerny, A First Glance at St. Thomas Aquinas, Chapter 13 (with special attention to the ‘text of the master’).

¹³ Here the word “before” does not necessarily mean before in time, but rather before in being (the second sense of before from chapter 12 of Aristotle’s Categories).

¹⁴ This was a problem for Descartes, for example.

¹⁵ A reminder that Aristotle distinguished three kinds of per se statements:

1. A statement is per se when the predicate is in the definition of the subject (e.g., every bachelor is unmarried, or every man is an animal).

2. A statement is per se when the subject is in the definition of the predicate (e.g., every line is curved or straight, every number is odd or even).

3. A statement is per se when the predicate belongs to the subject as to its proper cause (e.g., the swimming man got wet, the slaughtered animal died, a round thing casts a round shadow).

¹⁶ Recall the art about statements from logic.

CHAPTER 3

The Parts of the Soul

One way to understand any given subject better is to see if it is related to other things as whole to part or part to whole. Aristotle observes that often we know a part of the truth before we know the whole truth about something. So, if we want to advance in understanding about something, we should look to see if it is part of a larger whole or if it is a whole having parts we have not yet understood. That is what we are going to do next with the soul.

If we look at the kinds of living activities that a man performs, we notice that they have a definite relationship to the activities of other living things. Men can think, but they can also sense like an animal and grow like a plant. Not only that, but these activities of nutrition and sensation and reasoning can exist apart from one another (for example, a plant has nutrition, but not sensation or reason). This is a good reason to hold that the soul has different parts responsible for these separate activities. In some way, then, the soul of a man (a “rational soul”), which is responsible for all these living activities, must contain the soul of an animal (a “sentient soul”) and the soul of a plant (a “vegetative soul”).¹⁷ So the rational soul must be some kind of whole having the sentient and vegetative souls as parts, and similarly, the sentient soul must be a kind of whole which has a vegetative soul as one of its parts. But what kind of whole and parts are we talking about here?

Review of Kinds of Wholes and Parts

In logic we considered three main kinds of wholes and parts, but that was an entire semester ago, and repetition is the mother of learning. So it is good here to review these three main kinds of wholes and parts: integral wholes, universal wholes, and potential wholes.

The first kind of whole is called an integral whole: a whole which is composed of its parts like a house is composed of bricks and planks. This kind of whole is first because it is best known to us, and we have a natural tendency to fall back upon this best-known meaning of whole. The integral whole is the sum of its parts and the whole is not fully contained in any one of its parts. Therefore, neither do we call the part by the name of the whole. For example, we do not give the name “house” to one individual brick.

The second kind of whole is the universal whole: a whole which is said of each of its parts and understood to be completely in each of them. For example, animal is a universal whole which includes man, dog, and canary as parts. Here each part has the nature of the whole within it, hence the name of the whole is also said of each part. I can call a dog an animal, just as I can call a canary an animal. The whole notion of animal (living substance capable of sensation) is in each dog and each canary. So this case is very different from the integral whole. The parts of a universal whole are often called species or specific parts of the whole.

The third kind of whole is the potential whole: a whole which contains its parts in such a way that the whole can do everything the part can do and then some. In the potential whole, each part has the nature of the whole, but not according to its full power. Let’s take some simple examples of a potential whole: the ability to lift 100 pounds includes the ability to lift 50 pounds. The ability to lift 100 pounds and 50 pounds is the same kind of ability, the same nature, but the ability to lift 50 pounds does not have the full power of the ability to lift 100 pounds. Another example would be white light in comparison to colored light. White light and colored light both share the same nature: they are both colors, but colored light does not have the full power of white light. White light can be used to produce any color, such as red, blue, and yellow (as when it shines through a prism); but red light cannot produce white light. So white light is a potential whole which contains red and blue and yellow light as its parts. Since this is the least well known kind of whole, let’s give one more example: a Catholic bishop has the whole power of the priest and the deacon. The bishop can do everything the deacon can do (such as give blessings and preach) and everything the priest can do (such as consecrate the Eucharist and forgive sins), but then he can do more besides, like ordain new priests and consecrate the sacred oils. So the episcopacy is like a potential whole which includes the priesthood and diaconate as its parts.

So a potential whole is midway between an integral whole and a universal whole: the integral whole has neither the same nature nor the same power as its parts; the universal whole has both the same nature and power as its parts; the potential whole has the same nature but not the same power as its parts.

| Same Nature as its parts? | Same Power as its parts?
Integral Whole | No | No
Potential Whole | Yes | No
Universal | Yes | Yes

The Parts of the Soul

Now that we have reviewed the main kinds of wholes and parts, let’s see if we can determine what kind of parts the soul has. The soul seems to be an integral whole, since we see with our eyes, we hear with our ears, we eat with our mouths. Our eyes, ears, and mouth are different parts of our bodies, so perhaps our soul is also divided into parts just like our bodies are. And since our bodies seem to be integral wholes made of organs like a house is made of bricks, so too perhaps the soul is an integral whole composed of parts.

But if we look more carefully at the matter, using the definition of soul, we can see that the soul cannot be an integral whole. First of all, the soul is not a body or something having extension per se. The soul is a substantial form, something immaterial and unextended. But only things which are extended have integral parts. Secondly, if the soul were an integral whole composed of parts, then the whole soul would not be in each part of the body, but only a part of the soul would be in each part of the body. But since the soul is the substantial form of a living body, it is impossible for the whole soul not to be in every part of the body. Remember that a substantial form makes a thing to be what it is, simply speaking. So if the whole soul were not in every part of the body, the body would not be one substance, but each part of the body would be a different substance. For example, the eye would be one substance, the ear another, the mouth another. If that were true, then it would be more true to say that your eyes see than to say that you see by means of your eyes; or that your ears hear than that you hear by means of your ears. But our experience tells us the opposite: you are the thing which first of all sees and hears. For this reason you find it difficult to study when you have a toothache, and you find it difficult to walk or write when you have a headache. The pain of one member affects the whole body. You are one substance, not a heap of substances. Therefore, the whole soul is in each part of the body, so that the parts of the soul are not integral parts.

So maybe the soul is a universal whole, since the rational, sentient, and vegetative souls seem to be three species of soul: I can give each one the name “soul.”

But if we think about it more carefully, the soul cannot be a universal whole either. For then the parts of one soul would each be their own species and the whole soul would be several kinds of things at the same time. For example, the human soul, which contains the vegetative and the sentient soul, would at the same time be a rational soul, a sentient soul, and a vegetative soul. It would be like saying that one figure was actually a pentagon, a square, and a triangle all at the same time.

Therefore, the soul is a potential whole, since the whole includes the ability of its parts. For example, the soul which is capable of sensing is also capable of eating and growing. And the human soul, which is capable of reasoning, can also sense like an animal and take in nutrition and grow like a plant. So when we say that the soul has parts, we mean parts in the sense of powers or abilities, not parts in the sense of things in different places, or parts in the sense of actually different species.

Aristotle compares the soul to a figure based upon two likenesses. First, just as a general definition can be given for figure (a surface contained by sides), so a general definition can be given for soul (a substantial form of a natural, living body). Second, a figure with more sides potentially contains a figure with fewer sides. For example, a square contains a triangle potentially (by drawing the diagonal line, one could form an actual triangle). Similarly, the soul with more powers contains the soul with fewer powers potentially. For example, the animal soul contains the vegetative soul in its power or ability.¹⁸

Summary

• There are three main kinds of wholes: the integral whole, the universal whole, and the potential whole.

• The parts of the soul are its powers or abilities, so that the soul is a potential whole.

• The whole soul is in each part of the body.

• The human soul includes the power to reason, the power to sense and the power to take in nutrition.

_______________

¹⁷ Besides these three parts of the soul, Aristotle identifies two others: the part which desires (the “appetitive” part) and the part responsible for locomotion (the “locomotive” part). The appetitive part always exists together with the sentient part. In this course we will focus primarily on the vegetative, sentient, and rational parts of the soul, since these most of all pertain to the degree of perfection possessed by a living being.

¹⁸ Supplementary text: De Anima, Bk. II, ch. 3.

CHAPTER 4

Coming to Know the Parts of the Soul

It is important that we come to know the various parts of the soul, since if we do not, our knowledge of the soul will be so vague and general that it will not be a knowledge of any really existing thing. It would be as if we were to define “figure,” but never came to know any specific figure. “A surface contained by sides” is a general concept for any figure, but any real existing figure has to have a determinate number of sides: 3, 4, 5, and so on. There is no such thing as a really existing figure without some determinate number of sides. Similarly, there is no such thing as a soul without some determinate powers, such as nutrition, sight, and so on. Therefore, since the study of the soul is meant to lead us to a knowledge of real, living things, we must continue in our investigation to understand more distinctly the various powers possessed by the souls of real, living things.

The Method for Coming to Know the Powers of the Soul

If we are to come to know the powers of the soul, we must determine the right method to do this. In every case where we come to know something, the method we come to know it is by going from what is better known to us to what is less known to us. So we need to find out what is better known than the powers of the soul: that in terms of which we can understand these powers.

The first thing to see is that the powers of the soul do not seem to be directly known by us. They are internal to us and invisible to our senses. If I were to ask you to point out the power of someone’s soul, you could not do so directly. The powers of the soul are very close to our nature, and, as Heraclitus said, “Nature loves to hide”—that is, the things most intimate to our being are usually hidden from us.

Let’s take an example of a power of the soul: sight. How can we define sight? Well, we already have a genus: power or ability. But what should we use as the difference? Sight is the ability to _____. When you put it that way, it is clear enough that the word that fills in the blank is “see.” Sight is defined as the ability to see. “To see” is a kind of activity. So we define this power or ability in terms of its corresponding activity. Similarly with other powers of the soul. Touch is the ability to feel; hearing is the ability to hear, etc. Since we come to know the power and the activity very close to one another, we often give the same name to the power and to the activity: smell (the power) is the ability to smell (the activity); reason (the power) is the ability to reason (the activity). So the powers of the soul are understood and defined in terms of their corresponding activities. But what about the activities themselves? How should they be defined? Let’s take the example of sight again. To see, or seeing, is a kind of activity. What is the genus of this activity? Seeing is a kind of sensing. So all we have to do now is determine the difference. To see is to sense _____. It is obvious that the words that fill in the blank are color and light. Seeing is sensing color and light. Similarly, hearing is sensing sound, tasting is sensing flavor, etc. Color, sound, flavor—all of these are the objects of our sense powers: the things sensed. The activities are known and defined by their corresponding objects. These objects are directly known and sensed by us, so they are easy to point out and are not hidden from us. Thus, these objects can be the basis for a complete definition of the powers of the soul.

We can now formulate a general method for coming to know and define the powers of the soul. We must go from object to activity to power. This method of coming to know the soul is illustrated schematically below, together with a particular example.

Once we know the power, we can even go further and say what the essence or nature of the particular soul is. For example, we can say that the nature of the rational soul is that which is such as to be a principle of the rational power.

Summary

• Coming to know the powers of the soul helps us to know distinctly what the souls of real, living things are.

• The method of coming to know the powers of the soul is to go from object to activity to power.

CHAPTER 5

The Vegetative Power

Now that we have a method by which to investigate each power of the soul, we will now consider these powers one by one. The first question that comes up is “which power should we start with?” It might seem best to start with the sentient power, since the things closest to sensation tend to be better known to us. But Aristotle instead decides to begin with the vegetative power. Why? Because the vegetative power is common to all living things: plants, animals, and men. And we should treat what is common to a given subject before we treat what is proper to some subject, for otherwise students will get worn out by useless repetition. Besides this, our understanding of the vegetative power does not depend upon our understanding of the sentient power, so we are not violating the principle that we should go from the better known to the less known.¹⁹

Are Plants Really Alive?

When beginning his treatment of the vegetative power or principle, Aristotle begins by examining whether or not activities associated with the vegetative principles ought to be considered as living activities at all. For one must first determine that digestion, generation, growth, and the like are from a living principle before one can determine the nature of any specific living principle upon which these activities follow. The reason for this is that these activities seem as though they might be simply from nature rather than from a living principle. Moreover, life is more hidden in plants than in other living beings. For example, we see that inanimate things, such as stalagmites and fire, increase in quantity in a manner similar to the growth of plants, so it seems that plant growth and nutrition could be reduced to merely mechanical and material principles. So let’s begin by laying out some differences between the activities of living and non-living things. Because fire seems to present a special case, it has its own column.

Nutrition

Living | Fire | Non-Living
Nutrition is necessary to preserve its substance in being | Fuel is necessary to preserve its substance in being | Nutrition is not necessary to preserve its substance in being
Assimilates food into its own substance | Assimilates fuel into its own substance | Does not assimilate or transform external matter into its own substance
Uses organs to assimilate food into its own substance | Does not use organs to assimilate fuel | Does not have organs
When damaged, the living substance heals: the part acts for the sake of the whole | Parts do not act for the sake of the whole | Parts do not act for the sake of the whole

Growth

Living | Fire | Non-Living
Growth proceeds from an intrinsic principle (grows from the inside out) and by transforming another substance into its own substance | Growth happens by contact with fuel next to the fire. Growth is more by addition than by bringing external matter within itself and transforming it | Growth happens by addition to the outside surface, as happens with stalagmites
Living things always have some natural limit to their growth | No natural limit | No natural limit

Reproduction

Living | Fire | Non-Living
Always reproduces same kind of thing in a determinate form | Sometimes produces fire, sometimes another effect, and not in determinate form | Does not reproduce, only breaks into parts
Reproduces from within its own substance by way of a procession or “pushing out” of some part of itself | Produces fire in other things, but not always from within and not always by direct contact | Does not reproduce
Clearly defined generations from one individual to another | No clearly defined generations: “offspring” does not preserve individual or substantial unity | No generations
Adapts to environment from one generation to the next | New fires do not adapt | No adaptation

The differences listed above manifest that the activities of living things are different from the activities of non-living things in significant ways. Moreover, it seems that only in living beings do we observe an increase of order and organization. Unlike machines, plants come to be and develop from an intrinsic principle. Not only that, the part acts for the sake and the good of the whole. Finally, living things seem to act for the sake of preserving and propagating their kind or species, as if this is the ultimate good at which they aim. All of these indicate that plants are not just mechanisms composed of many diverse substances, each acting according to its own nature. On the contrary, a plant acts as a single substance having one species with a single good. But perhaps the best evidence of all that plants are really alive and really one substance is that we observe the same activities in ourselves and we experience them as the living activities of a single substance. Growth, nutrition, and reproduction in us are clearly manifestations of our life, and there is no substantial difference between these activities in us and in plants. Therefore, it is clear that these same activities are the result of a principle of life, a soul, in plants as well.

Living Fire?

Recall that in our comparison of the activities proper to living and non-living things, fire had a special likeness to living things. Aware of this, Aristotle saw that fire and heat had a special relationship to living things. Heat is involved in the digestion of food, so every living being uses fire, or at least some kind of heat, as an instrument for taking in nutrition. This explains why there should be likenesses between the activities of fire and the activities of living things, especially as regards the activity of nutrition. Nevertheless, fire is not alive, even though heat is an instrument of a living thing.

The Object of Vegetative Power

The vegetative power has three activities: nutrition, growth, and reproduction, of which the first and most basic is nutrition. We must therefore determine the object of the activity of nutrition in order to understand the nature of the vegetative power. Determining the object of nutrition is easy once you simply understand nutrition as eating. What do you eat? Food. Food is the object of the activity of nutrition. That was easy enough, but once someone asks you to define food, things become more difficult.

Food seems to be in the category of substance, since accidents cannot account for the nutrition and increase of a substance. But what kind of substance is food? Is it living or non-living? Surprisingly, the answer seems to depend both on what is eaten and what is eating. For a plant, soil and water are food, while for an animal, plants and other animals are food. So it seems that food can be both living and non-living. Besides this difficulty, what if there were no living things in the universe: no plants, no animals, no men? Would water and soil have the nature of food then? The same exact substances would exist, but I don’t think you would call them food, since they would not be nourishment for anything. Food seems to be relative to the thing that eats:²⁰ it is a substance which is capable of providing nourishment for a living thing.²¹

In his treatment of food, Aristotle states his position: “food is a contrary to what is fed: yet not every contrariety [involves feeding]; but only such contraries as find their increase as well as their origin in each other.”²² He then treats of a difficulty concerning how it is that contraries can account for one another’s increase (since contraries brought together normally destroy one another, as heat and cold). Finally, he resolves the difficulty by distinguishing between food as undigested and food as digested. As undigested, food is contrary to what is fed. But after the soul has acted upon the food, it is digested and therefore is similar to what is fed. So once food has been digested, the digested food can be the source of increase for the thing which eats.

Some questions arise about Aristotle’s method of defining food. First of all, why begin by defining food as a kind of contrary? That would make food seem to fall into the genus of opposition or something relative, but nothing eats or is nourished by a relation! I think one reason why Aristotle would do this is because he is treating food precisely as an object to the nutritive power, not merely as it stands in its nature. That is, it can be seen from Aristotle’s treatment of food as the object of the vegetative principle that food is not considered merely under the aspect of its own being, but rather it is considered as related to the being which it nourishes. For, in itself, every food would fall under the genus of substance, while in relation to what is fed, food has the nature of a contrary. Hence, we see that by “object” Aristotle does not mean a thing as it stands in its own being. Rather, an object of any power of the soul should be considered precisely as it relates to the soul. Now by saying that food is contrary to what is fed, he is implicitly indicating that it is in the genus of substance, since contraries share a common genus (recall the treatment of opposites in the logic text).²³

But why is food contrary to what is fed rather than correlative, or one of the other kinds of opposition?²⁴ Here again, Aristotle is very precise. In order for one substance to be converted into another, it must undergo a substantial change. But the kind of change which leads up to a substantial change is alteration (change of quality). The vegetative soul acts like an agent which uses the body and heat as its instrument to alter the food, eventually leading to a substantial change from food to the substance of the one eating. Now, when qualities are opposed to one another, such as hot and cold, black and white, it is clear that they are opposed as contraries. So, too, food before it is altered is opposed with respect to quality to that which it will become after the alteration. Therefore, food is most appropriately said to be contrary to what is fed before it is digested.

Defining the Activities of the Vegetative Power

But the activity of nutrition is not the only living activity performed by the vegetative power: growth and reproduction are also living activities. So Aristotle shows next (starting at 416b9) how food is related to all three activities of the vegetative principle. First, he shows that food is essentially related (as opposed to incidentally related) to an ensouled being. For if food were incidentally related to an ensouled being, then food would not essentially determine living activities. For example, a bicycle is incidentally related to living things, hence bicycle riding is not an essential division of a living activity. Then he proceeds to show that the distinction between the activities of nutrition and growth follow from the diverse ways in which food relates to each activity. For insofar as food provides substance to the ensouled being, this activity is nutrition. But insofar as food provides quantity to the ensouled being, this activity is growth. Finally, Aristotle relates food to generation where he says, “It is productive of generation, not of the one nourished, but of such a one as the one nourished.” Here generation is understood as being caused by food. For the seed, being produced from the ensouled being, must derive its source from the food consumed by the ensouled being (since all growth is due to the intake of food). But as a principle of the being of another, a seed is not of the substance of the one nourished; hence, the growth and production of a seed is a distinct activity from the growth or maintenance of the one nourished.

In this way we see how an understanding of food, as the object of the vegetative principle, provides a clearer basis for distinguishing the activities of the vegetative principle. For food is understood as the matter from which comes the substance, size, and offspring of an ensouled being. And it is only insofar as the activities of nutrition, growth, and generation are seen as specifically determining what the food becomes, that these activities are clearly distinguished. Hence, we define the activities of these as follows:

1. the activity of nutrition as the assimilation of food into the substance of an ensouled being;

2. the activity of growth as the assimilation of food into the quantity of an ensouled being;

3. and the activity of generation as the assimilation of food into the seed (i.e., principle of offspring) of the ensouled being.

Defining the Vegetative Power Itself Through its Activities

Finally, Aristotle defines the vegetative principle itself by relating this principle to the activities:

Wherefore, this soul-principle is a power able to preserve what possesses it as a thing of such a kind; and food is preparatory to the operation; hence, the being cannot continue deprived of food. Since there are three factors: what is nourished, that by which it is nourished, and that which nourishes; what nourishes is the primary [i.e., vegetative] soul, that which is nourished is the body containing it, and that by which it is nourished is food. Since all things are rightly named from their end, and the end [of this principle] is to have generated another being like itself, then the primary soul is generative of what is like itself.²⁵

Here Aristotle seems to provide us with two definitions of the vegetative principle, or primary soul: “a power able to preserve what possesses it as a thing of such and such a kind;” and that which is “generative of what is like itself.” The second definition is the most perfect since it says more fully what the vegetative principle is. A simple example will make this clear. Let’s say that your maximum bench press is 200 pounds. If someone were to ask you “how much can you bench press?” what would be a more complete answer, 100 pounds or 200 pounds? Both would be true, since you can bench press both weights, but the second would be more complete, since we define a power by its maximum ability. Similarly, since the ability to reproduce includes and presupposes the ability to eat and the ability to grow, and since these two abilities are ordered to and for the sake of reproduction, it is clear that reproduction is the maximum ability of the vegetative power. So the most complete definition of the vegetative power is the ability to generate a living thing like itself.

Since art imitates nature, and since art is often better known to us, sometimes it is helpful to use an analogy from a man-made artifact as a way of understanding something natural like the soul (Plato does this in his Republic where he compares the soul to a city). So let’s take the example of an abbey as an analogy to a living being. An abbey takes in new seminarians and sometimes it also loses people, either because the confreres die, or decide to leave, or whatever. When an abbey takes in as many persons as the number of persons it loses, then the abbey is able to preserve itself in existence. It remains stable at the same size. This is like nutrition, where the soul is able to preserve the living being in existence. But if the abbey loses more people than the number of people who enter, the abbey will shrink and eventually die. On the other hand, if the abbey takes in more people than it loses, then the abbey grows. This is like the growth of a body. This growth also makes development possible. As a living body grows, it also develops, forming and perfecting new organs until all the organs necessary for a perfect living member of its species are present. At this point, the living being is fully mature and capable of reproduction, so that additional food beyond what is necessary for nutrition and growth can be used to produce seed.²⁶ Similarly, when an abbey takes in so many seminarians that it is able to grow and develop all the organs necessary for the operation of a perfect abbey (with an Abbot, a Prior, teachers, cantors, enough people to attend to the fitting worship of God, sufficient confreres to maintain the grounds, etc.) then the abbey is now able to found a new abbey, and this is like reproduction in a living body.

Some Difficult Cases

From the outset of our treatment of living things, we have insisted on beginning with things that are obviously alive, like ourselves and horses, etc. This is so we could start with what is better known to us about life. We stayed away from tough cases like fungi and viruses, since hard cases make bad philosophy (at least if we start with them). But now that we have a better idea of what it means to be alive, it is reasonable to ask the question: are fungi or bacteria or DNA or viruses alive?

It seems to me that things like fungi and bacteria are, for the most part, complete organisms capable of nutrition, growth, and reproduction. On the other hand, things like DNA and viruses do not seem to be able to carry out these activities unless they are part of a larger whole, part of a complete substance or organism. So it is better to say that DNA or a virus is potentially alive or able to be part of a living thing. But in themselves, these things are not actually alive.

Summary

• The vegetative power is common to all living beings, so it should be treated first.

• The activities of nutrition, growth, and reproduction are properly living activities and differ significantly from the activities of non-living things.

• The object of the vegetative power is food.

• Food is not defined merely as a kind of substance, but also insofar as it relates to something capable of being nourished.

• The activities of nutrition, growth and reproduction are all defined in terms of food.

• The vegetative power is defined in terms of its maximum ability, namely reproduction.

_______________

¹⁹ However, our understanding of the vegetative power does depend upon what we know through our senses. We don’t have to know the vegetative power through knowing sensation, but we do come to know our vegetative power through sensation. It is one thing to know B through A. It is another thing to know B through knowing A.

²⁰ More precisely, food seems to be relative to the way we speak (secundum dici), since it is said to be toward a nutritive power not in its very nature (since it is a substance of some kind), but rather because a relation follows immediately upon the action of the nutritive power on food.

²¹ At this point, the students should read chapter 4 of Book II of Aristotle’s De Anima. Read the text in class, discuss it; and then come back to this point in the text.

²² De Anima, Bk. II, ch. 4 (416a21-22).

²³ Logic, chapter 7, part c: Getting from Genus to the Species.

²⁴ A reminder may be due that the four types of opposition are: correlatives, contraries, having/lacking, and affirmation/negation.

²⁵ De Anima, Bk. II, ch. 4 (416b17-25).

²⁶ By the way, this seems to be one reason why fasting helps to overcome concupiscence (excessive sexual desire). If more food is taken in than is necessary for nutrition and growth, the extra food can be dedicated to seed. This causes the body to desire sexual activity more ardently.

CHAPTER 6

Sensation in General

Aristotle observed that the characteristics most often associated with life are self-movement and perception. In plants, only limited forms of self-movement (growth and reproduction) are found: hence the difficulty in identifying plants as alive. It is in animal life that the activities most fully associated with life are found. This is why the Latin word for soul and life (anima) is derived from the Latin word for animal. Animals differ from plants primarily because animals possess sensation. Some animals possess multiple senses, some animals possess one only (the sense of touch), but all are animated. All are animals. We will first consider sensation in general, after which we will briefly consider each of the senses separately.

What is Sensation?

In defining sensation (meaning the power of the soul) we shall follow our method of going from object to activity to power. But, as usually happens, philosophy is not just a mechanical process of plugging in data to a method or a formula. Reality is just too complicated and intricate for that kind of approach. Defining the word sensation involves many difficulties, and often, in my experience as a teacher, I find that students don’t even know where to begin. For example, it’s easier for students to define sight or hearing than sensation in general. It’s like the case in Plato’s dialogue, the Meno, when Socrates is asking Meno for a definition of virtue:

Socrates: What do you yourself say virtue is?

Meno: There is no difficulty about it. First of all, if it is manly virtue you are after it is easy to see that the virtue of a man consists in managing the city’s affairs capably, and so that he will help his friends and injure his foes while taking care to come to no harm himself. Or if you want a woman’s virtue, that is easily described. She must be a good housewife, careful with her stores and obedient to her husband. Then there is another virtue for a child, male or female, and another for an old man, free or slave as you like…

Socrates: I seem to be in luck! I wanted one virtue, and I find that you have a whole swarm of virtues to offer.²⁷

We tend to give examples before definitions, and similarly, it is easier to give examples of sensation—seeing, hearing, feeling, etc.—than to define sensation.

As often happens when we do philosophy, we need to go back to our trusty friend logic and recall that often it’s best to start with a nominal definition since we know what a word means before we know whether or what it corresponds to in reality. So let’s start there, with a nominal definition of sensation. By the word sensation I mean whatever seeing, hearing, smelling, tasting, and feeling have in common.²⁸ For all of these are kinds of sensing. No one can deny that there is some reality corresponding to the name sensation. So sensation really is a kind of being. There might be doubts about what we sense or how sensation can happen, but there is no doubt that we sense. Sensation is not a name like mermaid or chimera: it names something we are certain exists, even if at first we have a hard time saying exactly what sensation means.

So what do things like seeing, hearing, and feeling have in common? First of all, all of them seem to involve “taking in” the world around us. More precisely, each of the senses “takes in” various qualities. We see color, we taste flavor, we feel heat. All of these are qualities: more particularly, they are affective qualities belonging to the third species of quality enumerated by Aristotle in his Categories. So we can say that just as the particular object of sight is color, and the particular object of taste is flavor, etc., so we can also say that the object of sensation in general is affective qualities, that is, qualities which somehow act upon our sense powers.

Sensation is at once a “taking in” and an activity. In relation to the thing or object sensed, we do not do anything to the thing we sense: when we see, we are not acting upon the color, rather it is acting upon us; when we hear, we are not acting upon the sound, but it is acting upon us. Even in sensing heat, while our hand may absorb some heat when it comes in contact with the hot thing, this heat is not absorbed in virtue of the fact that we sense it: a numb or even dead hand absorbs just as much heat as a sensing hand. The sensing itself does not affect the thing sensed. Not only this, but we cannot sense something if the object sensed is lacking: unlike imagination, the activity of sensation depends upon some external object. Sensation cannot arise wholly from within the one sensing, but presupposes that some external object act upon the sense organs. Thus, if we were to place sensation in one of the ten categories, we would have to say that sensing is an undergoing rather than an acting upon.

In relation to the sensing subject (i.e., the one who is sensing), sensation seems to be an activity or even akin to a motion. When we are awake and our senses are fully engaged, we are more active. Sensation seems to perfect an animal or make the animal more actual. Everyone knows that a man who is awake is better than one in a coma. So sensing seems to be an activity in the sensing subject when the sensing subject takes in sensible qualities.

This two-fold dimension to sensing—namely, (1) that it involves the reception of sensible qualities and (2) that it is an activity or kind of motion in the one sensing—indicates that sensing seems to be very much like the undergoing a subject experiences when it is being altered. In alteration (i.e., change of quality), the thing being altered (1) receives some new quality and (2) undergoes a motion as it receives the new quality. As an apple ripens from green to red, it is at once receptive of a new quality and the subject of a motion. This likeness between sensation and being altered is further confirmed by the way in which we speak about certain machines “sensing.” Take the example of a heat “sensor.” Many heat sensors are made from a metal coil which expands when heated. When the expansion is great enough, the metal coil touches an electrode and completes an electric circuit which sets off an alarm. In this example, the sensor is altered by receiving a sensible quality, namely, heat. Can the heat sensor be said to “sense” heat in the same way in which a hand senses heat? Is sensation merely alteration then? The following section examines some significant differences between sensation and alteration.

Sensation versus Alteration

The proper objects of all our external senses are qualities. More specifically, they fall within the third species of quality: affective qualities. These are qualities which are capable of altering or otherwise acting upon other subjects. For example, heat is a proper object of the sense of touch, sound is the proper object of the sense of hearing, color is the proper object of the sense of sight. Each of these qualities are capable of producing a qualitative change, that is, an alteration, in some other subject. The question is: granted that these affective qualities produce an alteration in our sense organs (for example, heat causes our hand to warm up) is sensation the same thing as this alteration, or something different from it? The following chart outlines some differences between sensation and alteration.

Alteration | Sensation
Alteration is in and of the same thing. For example, when water is being heated the motion of heating is in the water and of the water. | Sensation is in one thing but of another. For example, I sense the color of an apple, although the sensation is in me.
The subject which is altered becomes what it receives. For example, when an apple is being altered from green to red, it becomes red. | The subject which senses does not become what it receives. For example, when I sense red my eye does not become red.
A thing which is altered receives some quality by losing some other quality. For example, water becomes seventy degrees by losing some other temperature, or an apple becomes red by losing green. | In sensation, a quality is sensed in virtue of having some other quality. For example, a man senses seventy degrees only when his hand is lacking seventy degrees, or a man sees yellow only when his eye is lacking yellow.
Alteration destroys the form which was possessed before. | Sensation perfects that which was possessed before.
When a thing is undergoing alteration, it has not yet reached the term of the alteration. For example, that which is becoming black is not yet black. | When a thing is sensing, it has already sensed. For example, when a thing is sensing black, it has already sensed black. Sensation is completed in an instant.
Alteration can be fast or slow. | Sensation is not fast or slow.

The first two differences are pretty obvious, but the last four differences may need some additional explanation. When something is altered it has to lose that quality which it had before. Why is this? Because it can only possess one quality at a time: to become hot, a surface needs to lose cold; to become black a surface needs to lose white, and so on. So whenever a thing receives a new quality in the process of alteration, it loses the quality it had before. But the opposite happens in sensation. Sensation also involves receiving a quality. For example, my hand receives heat when it senses heat. But my hand does not need to be hot in order to receive heat in the process of sensation (in fact, if my hand is warm, I can’t sense that same warmth in something else). In sensation, I can possess two qualities at the same time: I sense heat while my hand is cold, I sense color while my eye is transparent. Related to this difference is another difference: alteration destroys the quality that was there before, but sensation perfects what was there before. A sensing, awake man is more perfect than a sleeping man or a man in a coma who is not sensing. Sensation is the realization of an ability, not the replacement of an opposite quality. So sensation perfects rather than destroys the way alteration does.

Sensation is also something that is completed in an instant. This is the opposite of alteration. Alteration takes time. It takes time to heat my hand from cold to warm, but when my hand touches something warm, I begin sensing that warmth (even while the hand is still cold). Similarly, it makes perfect sense to speak of an alteration being fast or slow. For example, heating water can happen slowly or quickly. But since sensation happens in an instant, it makes no sense to speak of sensing heat slowly or quickly. These differences show that sensation cannot be identified with alteration. Yet what is the basis of this difference? If we examine the chart above, we notice that there are two fundamental differences between sensation and alteration. First, in sensation, the sensible form (e.g., the quality of color or heat, etc.) is received in the sensor in a different way than a quality is received in a subject that is altered. That which is altered receives the quality as its own form, in such a way that it is named by that form, and must lose some other form in order to acquire the new quality. That which senses receives the quality, but not as if the quality were its own form. Rather, the quality received in sensing retains its relation to the object sensed: it is the form of the object sensed, even though it is in the sensor. The red which is sensed is still the red of the apple, even though this redness is somehow in the one sensing. This is why the sensor is not named from the form which it senses: if I sense red, I am not said to be red. To have sensed red is not to be red, but to have been altered to red is to be red. This is also why the one sensing does not have to lose some form when it senses another form: because it is acquiring that other form, not as its own form, but as the form of something else.

The second fundamental difference between sensation and alteration is that sensation cannot be a motion in the strict sense. Motions happen over time and can be fast or slow, while sensation happens all at once, instantaneously, and therefore cannot be fast or slow. Recall the definition of motion from natural philosophy: the act of something potential insofar as it is potential. A motion in this strict sense of the word is something not yet actual, but still in a state of potency with regard to the term of the motion. The apple which is ripening is not yet red, but is still able to be red. But with sensation, the potency of the sense power is actualized in the first moment of sensation: you are sensing red from the very beginning. So while there is an activity happening in the one sensing, this activity is not motion, but something more perfect than motion. Not only that, but the thing which is potential in a motion (say, the apple) and the thing which is potential in sensation (the power of sight) are potential in two different senses of the word. The apple is in potency to have red, but only if it loses green. The power of sight is in potency to sense red, but in such a way that it doesn’t lose some color it had before. Your ability to see is not colored the way the apple is colored, so the power of sight is in potency to color in a different way than the apple is.

Sensation Distinguished from Understanding

Aristotle treated sensation as a kind of mean between alteration and understanding or intellectual knowing. This approach allowed him to simultaneously distinguish sensation from alteration and understanding. We have already seen many likenesses and differences between sensation and alteration. It will be helpful here to lay out how sensation is in some way like understanding, while at the same time distinguishing them from each other. By showing that sensation shares something in common with both understanding and alteration, it will become evident how a deeper knowledge of sensation can serve as a bridge from a knowledge of alteration to a knowledge of understanding.

Sensation involves being moved and acted upon. Sensation requires that some agent act upon the one who senses, and that the one who senses in some way be moved from a state of potency to act. Something similar happens whenever we come to understand some object. Some object, such as a tree, acts upon our knowing powers in such a way that we are moved from merely being able to understand a tree to actually understanding it.

Moreover, in both sensation and understanding, there seems to be a double movement from ability to actual knowledge. For example, when someone is completely ignorant about geometry, they are only able to learn about it. But once they have learned geometry, they have a habit of geometry, so that they are able to think about it at will. So there are two levels of ability or potency: a first potency which is just a potency to come to know (for example, a boy has the potency to learn geometry while a tree does not), and a second potency which is a potency to actually consider some knowledge (for example, a boy who has learned geometry is able to exercise his habitual knowledge of geometry while someone who has not learned geometry has no potency for this). So with understanding, there is a double movement from potency to full actuality. Something similar happens with sensation. There is an ability to receive the power of sensation (for example, in something which is about to become a mature animal) followed by the ability to exercise that power of sensation (as when a mature animal wakes up and begins to actually sense). As Aristotle puts it, “The first change in the sensitive being is caused by the parent. When it is born it is already endowed as with [habitual] knowledge. Actual sensation corresponds to the act of thinking.”²⁹

Nevertheless, there are also significant differences between sensation and understanding. The change from potentially sensing to actually sensing always comes from an external agent, while the change from potentially understanding to actually understanding is caused by an internal agent. This is because sensation has particular objects which are outside of us, while universals are in a way in the soul.

Do We Sense Things in Themselves?

This aspect of our experience of sensation raises a further question: How do we know that what we are sensing is really out there? How do we know that the color in the wall is really how the wall is? How do we know that the flavor in the apple is really something in the apple and not just the product of neurons and chemical representations in our nervous systems? A more complete answer to these questions may have to wait until the end of this book when we take up the problem of subjectivism, but for now there are a few basic observations which the student should keep in mind.

First, the only way we could claim to have knowledge of neurons, chemical representations, nervous systems, or even of our own subjective sense powers, is through the objects which we directly sense. In our knowledge, the less known depends upon the better known. So unless we know colors and shapes and flavors and hot and cold, etc., we don’t know any of those other things. We reason to the fact that we have a nervous system and chemicals, etc., based upon the fact that our senses reliably present reality. So denying the objective value of what we sense based upon what we now know about our nervous system would be like denying the possibility of adding two numbers based upon what we know about multiplication (since multiplication depends upon and is understood in terms of addition).

Second, when we sense color in a wall, or flavor in an apple, we experience that color as a quality belonging to the wall, and that flavor as a quality belonging to the apple. To deny that those qualities, those forms, are in those other things is simply to deny our experience of sensation. Remember: philosophy must explain our experiences, not replace or explain away our experiences. Our account of sensation demands that we be faithful to two facets of our experience: (1) that sensation is happening in us, but (2) it is of something outside of us. If we were to give some other account that denied that the qualities sensed are outside us, then it would not correspond to what we mean by the word sensation in our everyday language.

For example, if I were to say that when I sense the white wall, I do not experience the white as something in the wall, then you would not be talking about sensation, but something else. One of the things this philosophy course is supposed to teach you is that any scientific knowledge you may acquire presupposes a pre-scientific knowledge that is more certain. You have been using the word sensation since you were a child. You did not need to take a class in physics or biology before you were able to use the word sensation correctly. Therefore, the meaning of sensation is not taken from some special scientific investigation, but rather can be derived from everyday experience. It may not be clear right now why or how sensation is possible, but that it is our experience can’t be doubted. Fortunately, you don’t have to answer the question about how sensation is possible to see the truth that sensation happens. You are certain that you are reading, even if you know nothing about how the brain processes all that information to make reading possible. Those are simply two different questions.

A Definition of Sensation Which Conforms to Experience

The difficulties which lead someone to think that we are not really sensing things outside of us are based upon the confusion between sensation and alteration. Attempts to account for sensation in the same way we explain the operation of a heat sensor or other machine begin by assuming that sensation is alteration. In physical motions, an agent gives some form to a patient. For example, fire gives heat to water. But once the heat has passed from the agent to the patient, it is no longer the agent’s form, but the form of the patient. The heat in the water is no longer the heat of the fire, even if it is heat from the fire. It is not the same with sensation. I see the color of the chair, I feel the heat of the metal. We experience these affective qualities, these forms, not as ours, but as belonging to the thing we are sensing. When we define sensation, we must include this in our definition. Hence, sensation must be defined as the reception of the affective quality of another thing, precisely as other: the form (i.e., the affective quality) remains the form of that other thing, even when we are sensing it. This definition of sensation is in respect to the object sensed. As mentioned above, in another way, sensation can be understood in relation to the power of sensing. Considered from this perspective, sensation can also be defined as the actualization of the ability to possess the affective quality of another thing, as other.³⁰

Immateriality: the Reason Why Sensation is Possible

Since our experience of sensation demands that we receive the forms of other things, and since it further demands that they remain the forms of those other things even when they are in us, it follows that these forms have to be received in an immaterial way. We are not receiving the form together with its matter. When we sense the color of the chair, we are not receiving that color together with its matter, otherwise we would have a physical chair in our eye. Nor does the color of the chair inform our matter (if it did, then it would be our form and no longer the form of the chair, as in the above example of heat in fire and the water heated by it). From this it can be seen that sensation can also be defined as the reception of the form (affective quality) of another thing in an immaterial way.

The same conclusion follows if we consider sensation on the part of its proper subject (i.e., the thing in which sensation takes place). The form is not received in the prime matter of the sensing subject, since prime matter only receives substantial forms: something cannot be in some accidental way unless it first exists simply speaking (i.e., as a substance). Nor is the form received in the sensing subject so as to inform the physical body of the one sensing (i.e., the body which is a composite of prime matter and substantial form). For if the physical body of the sensing subject were to receive the form of the various qualities sensed, then sensation would be the same as alteration. Therefore, only one possibility remains: the forms of the sensed qualities are received into the substantial form of the one sensing. That is, they are received into the soul of the one sensing. And since they are received into an immaterial thing (a substantial form), they must be received in an immaterial way.

The proof that sensation involves receiving the forms of other things in an immaterial way can be expressed in the following either-or syllogism:

Either

A) The forms of other things are received with the matter of the thing sensed; or

B) The forms of other things are received in the matter of the one sensing; or

C) The forms of other things are received without matter.

But not A) since when I see a chair, the wood of the chair is not in my eye; and

not B) since my eye does not become blue when I see a blue chair Therefore C) the forms of the things I sense are received in an immaterial way.

The Definition of Sensation Explains Our Experience

The above definitions of sensation explain why the forms of things which are sensed are in one thing but of another thing, for when a form is received into matter, it is limited to that subject and that subject only. The red of this apple cannot be the red of that apple. But a form which is not received in a material way is not limited or contracted by matter: it can remain open to subjects other than the one sensing. The red I am sensing can be the red of that apple.

This understanding of sensation also explains why sensation is not like physical motion: motion is the act of something in potency, but matter is that which is potential, while form is something actual. If sensation were the reception of the forms of sensible qualities into a material subject in a material way, then sensation would necessarily be a motion which gradually passed from pure potency to pure act. But since the forms are received in something which is not a material subject (i.e., the soul which is the substantial form of a living body), then the change which takes place in sensation happens all at once.

The definition of sensation, while it remains true to the data of our experience, raises further difficulties. For example, it is difficult to see how the form of one thing can be in another thing. Our experience of sensation requires that the same thing exists in two ways. For every thing sensed has its own being and being in the one who senses. Strange as this may sound, it is not impossible. There is nothing in the notion of being requiring that it be contracted to one subject only. In fact, we have already seen in the case of the category of things which are relative (toward another) that they have a two-fold being: being in one thing and being toward another thing. Fatherhood is in your father, but it is also toward you. Without both kinds of being, such relations would not exist. To give a full and detailed account of how one thing can have multiple existences is outside the scope of the science about the soul. It belongs to a higher science, called metaphysics, to complete this task. Nevertheless, what we have said here is sufficient to manifest that (1) our experience demands that sensation be defined as something in one thing and of another, and that (2) this involves no absurdity or impossibility.

Defining the Sentient Soul

Now that we have arrived at a definition of sensation, we can define the sensitive soul as a soul which is capable of receiving the forms of sensible qualities in an immaterial way, or alternatively, a soul which is capable of receiving the forms of sensible qualities in such a way that these forms remain the forms of something else.

The Object of Sensation Revisited

We have been assuming throughout this consideration of sensation that the object of sensation is some affective quality. However, someone might rightly object: I sense more than just affective qualities. I sense motion, shape, size, people, dogs and trees, none of which are affective qualities. Shapes are from the fourth species of quality. Size is in the category of quantity. Trees are in the category of substance. Motion is in a number of different categories. So why say that the object of sensation is an affective quality?

The first thing to notice is that while you do sense all of these things, you sense them in different ways. If you see the shape of something, it’s only because you see its color. If you hear motion, it’s only because you hear a sound that’s changing. And with respect to our external senses (seeing, hearing, feeling, etc.) sensing a tree or a man seems even further removed. We don’t seem to sense substances directly with our external senses, but only indirectly, through their qualities and shapes, etc.³¹

Because of these different ways in which we sense, Aristotle divides up the objects of sensation into the per se (sometimes called direct) objects of sensation and the per accidens (sometimes called indirect) objects of sensation. Substances like trees and dogs and men are per accidens objects of sensation. They are not sensed in themselves by any external sense. On the other hand, the per se objects of sensation are subdivided into the proper objects of sensation (color, sound, flavor, etc.) and the common objects of sensation (shape, size, number, motion). The proper objects of sensation are those objects sensed by only one sense power: they are proper to that power. So color is proper to sight, sound to hearing, etc. Aristotle notes that with regard to these proper objects of sensation, the sense power never fails and is never deceived.³² The common objects of sensation are objects sensed by all the sense powers in common. Thus, I can sense motion with my eyes and with my hearing and with my touch, etc., as the following chart summarizes:

The important thing to understand is that all sensation reduces back to the per se and proper objects of sensation, and these are affective qualities. So this is why we said at the beginning that the object of sensation is some affective quality.³³

Summary

• The nominal definition of sensation is whatever seeing, hearing, smelling, tasting and feeling have in common.

• The essential definition of sensation is the reception of the affective quality of another thing as other.

• Since the reception of the form of another thing, as other, requires immateriality, another definition of sensation is the reception of the affective quality of another thing in an immaterial way.

• Sensation is like being altered in three significant ways:

1. it involves receiving;

2. affective qualities are received; and

3. both seem to be a kind of motion.

• But, sensation is unlike being altered in significant ways:

1. the affective qualities are received as the form of another, not as the form of the one sensing; and

2. the activity involved in sensation is not the same as the motion involved in being altered.

• In general, three objects of sensation are the proper and per se objects, the common per se objects, and the per accidens objects.

_______________

²⁷ Meno, 71d-72b.

²⁸ By “seeing” I mean simply “that which someone can do only with his eyes.” Likewise by “hearing” I mean simply “what someone can do only with his ears.” Similar nominal definitions can be given for the other senses.

²⁹ De Anima, Bk.II, ch.5 (417b16-19).

³⁰ Thus, Saint Thomas observes that the proper act of any ability is in the same genus as that ability (cf. Summa Theologiae, Ia, q.77).

³¹ We are speaking here about sensation through the external senses of sight, hearing, smell, taste, and touch. There may be another internal sense power by which we somehow sense substances per se. But this consideration will have to wait until the next chapter.

³² We will investigate objections to this claim in the next chapter.

³³ Supplementary text: De Anima, Bk. II, ch. 6.

CHAPTER 7

The Five External Senses

Now that we have a good idea about what sensation is in general, we next turn to examine each of the senses in particular. There are two kinds of sense: external senses (since their proper and direct object is wholly external to us) and internal senses (since something of their object is internal to us). We will consider the external senses in this chapter and the internal senses in the next chapter.

As we learned in childhood, human beings have five external senses: touch, taste, smell, hearing, and sight. More perfect animals have all five of these senses.³⁴ We will briefly take each up one by one, beginning with their proper objects.

The Sense of Sight

To begin with some obvious facts about the sense of sight: the organ of the sense of sight is the eye and the object of sight is both color and light. Hence, we can define sight as the ability to sense color and light by means of the eye. Notice that the organ of sight, the eye, includes not only the spherical part of the eye in the eye socket, but also the retina, the optic nerve and, probably, part of the brain which are also necessary for the sensation of sight, as many experiments show.

The Object of Sight

Color is that affective quality in a surface which is visible of itself. Notice that color is correlative to the power of sight, in a way like food is correlated to that which eats. If there were nothing able to eat in the universe, then nothing would be called food, even though it would be the same being in itself (e.g., water would be the same kind of substance, but it wouldn’t be considered a kind of nourishment for anything). Similarly, if there were no power of sight, we would not call this affective quality in the surfaces of bodies “colors,” even though it would remain the same being in itself. Part of what it means to be colored is to be visible.³⁵ The objects of sensation are objective natural realities, but part of what we mean by them includes our own subjective experience of them. So there is both an objective and a subjective element in their definitions. We should note this difference between color and food, however: food is the object of an active power of the soul, while color is the object of a passive power of the soul. The soul acts upon food to change it into the substance of the eater. Conversely, color acts on the power of sight, so that the soul is in some way changed by the color.

As we already mentioned, many people today want to deny that colors are really in things or that our sensation of color has any real correspondence to what is actually in the surfaces we are seeing. And indeed, many objections might be made to this effect based on the differences in the perceptions of those who are color-blind and those who are not, as well as the findings of the experimental sciences, etc.

To say something briefly about color blindness: we have no difficulty in telling the difference between people who are color-blind and those who are not. Not only that, but we can tell that color-blind people are defective in relation to those who are not color-blind. People with healthy organs of sight can distinguish colors that color-blind people cannot (red from green, for example). So both doctors and painters are aware that there is an objectively more perfect apprehension of reality in those who are not color-blind. Our judgment that those who are color-blind are in an objectively defective state with regard to their power of sight is not the result of social conventions or what’s normal any more than nearsightedness is. Even if most people were nearsighted (which is probably true), we would not say that the people with clear vision are defective. Similarly, even if most people were color-blind, we would not say that those who were not had defective vision.

As far as the findings of optics and modern experimental science are concerned, here again it is good to recall that the word color has been used by you correctly for a long time. You know what it means without having to read a book on the physics of optics. Physics and the experimental sciences do not make us cease to know what we knew before by offering to us a replacement for our experience; rather, if pursued correctly, they refine our experience. So you do not suddenly mean something different by color after reading a physics book than before: your pre-scientific experience of color hasn’t changed one bit, so neither does your first definition of color need to be rejected. Indeed, it may happen that we discover that things like photons and wavelengths are closely related to color. Such things might tell us about the causes or effects of what we experience as color, and they might even help us make a more refined definition (by adding certain causes or properties to our definition), but they do not make color not to be experienced by us as an affective quality. The color in a wall may be the cause, for example, of wavelengths, but the wavelengths are not the color.³⁶

Not only color, but also light is sensed by the power of sight. Nevertheless, we distinguish color from light in our experience. Color is a quality in a surface, light seems to be something diffused throughout a volume or space. Light also seems to be something more active than color.

If you are a typical product of a modern education, you will likely have heard that light is both a particle and a wave. You will have heard all about photons emitted when electrons change energy levels, about diffraction experiments, and so on. It can all get very confusing. If this is your quandary, just remember what I keep telling you: you were able to use the word light correctly well before you ever heard of a photon or particle-wave duality. It still makes perfect sense to say that “light is shining through the window,” and “I couldn’t see until there was light.” Not only that, but you can be certain that someone who says that light is both a substance (a particle is a kind of substance) and an accident (a wave would be a kind of relation) is wrong. Substances exist on their own; accidents do not exist on their own, but in another. So it would be a contradiction to say that a substance is an accident. Every experiment anyone has ever done to supposedly show that light is both a particle and a wave assumed the fact that contradictory statements are not both true as a basis for their conclusions.³⁷ To be sure, there is irrefutable evidence that particles and something like waves are essentially linked to what we call light. However, these things are not light itself, but must rather be causes or effects of the light which we experience and which we are now defining.

So let’s go back to the light we have been talking about correctly since we were two years old. Our first clue is that light is sensible, so, like color, it must be an affective quality. That’s the genus of our definition. Where is this quality to be found? Not in surfaces like color, but rather in the space between some surface and our eye. Let’s call this space or volume the medium of light. In order for us to see anything, there must not only be some colored thing, but also some distance, some medium, between our organ of sight and a colored thing. If I touch a red cloth right to my eyeball, I won’t see red. There needs to be some medium before I can sense red. This is where light is found: it is a quality of this medium. Will any medium do as the proper subject of light? No. Some things just can’t be illuminated: brick, wood, metal; all of these are opaque. So only transparent things are the proper medium of light: air, water, etc. When I’m in a room with no light in it, the room is completely black. Even if the colors of the walls in the room are vivid and bright, they are not seen so long as there is no light in the room. But once light is allowed into the room (e.g., when a shutter is opened, or a light bulb is turned on) suddenly the colors on the walls can be seen. Is this because light makes the walls to be actually colored when before they were only potentially colored? No, the colors were actually there all along. But the reason they couldn’t be seen was that the air wasn’t actually transparent. The light didn’t make the walls to be actually colored, but it did make the air to be actually transparent.³⁸ So light is a quality which makes a potentially transparent medium to be actually transparent. In other words, light is the act of the transparent medium. This is clearly what we mean by the word light. We leave it up to the experimental physicist to determine how photons and waves are related to this quality in the medium.³⁹

Error in Sensing Color and Light

It was mentioned above that Aristotle observed that we do not err with regard to the proper objects of sensation. But what about optical illusions? For example, at a distance mountains look blue, but when I get close they are brown. Or the man with jaundice sees a white wall as if it were yellow. In these cases, and others like them, the eyes are in fact sensing a real color. The blue seen when looking at the mountains and the yellow seen when looking at the wall are real colors. The mistake is made in judging that they belong to the mountain or the wall. The blue is in the medium (the air) between the eye and the mountain, while the yellow seen by the man with jaundice is in the fluid of the eye itself. So the senses are not deceived in these cases. Similarly, whenever a sense seems to be deceived with respect to its proper object, the deception is not with respect to the proper object itself, but rather with respect to the subject in which it is, or some such thing.

The Sense of Hearing

Having treated the sense of sight in some detail, we will only briefly treat the other external senses. The organ of hearing is the ear, and the proper object of hearing is sound, so that hearing may be defined as the ability to sense sound by means of the ear. Sound is that affective quality of a body which is audible of itself. Sound comes about when a body is struck in such a way as to produce rapid, uniform vibrations. Sound is more effectively generated when the body is so formed so as to be able to move the medium together. Hence, soft bodies, or bodies which are not such as to be susceptible to uniform vibration produce little or no sound. Like color, sound needs some medium in order to be heard. Air, liquid, or some such medium capable of propagating rapid vibration is the proper medium of sound.

The Sense of Smell

The organ of smell is the nose, and the proper object of smell is odor, so that smell may be defined as the ability to sense odor by means of the nose. Odor is that affective quality of a body which is smellable of itself. Odor comes about when heat acts upon a body which is disposed to produce odor. Like color and sound, odor needs some medium, whether air (for human smell) or liquid (for example, for sharks) which is able to be moved and infused by the quality of odor.

The Sense of Taste

Of all the senses, taste and smell seem to have the most affinity. In fact, those lacking in one of these often have defects in the other. If someone born without the sense of smell were to ask what smell is like, he could get a pretty good idea from a description like “smelling is like tasting at a distance.” The organ of taste is the tongue, and its object is flavor, so that taste can be defined as the ability to sense flavor by means of the tongue. Flavor is that affective quality of a body which is tasteable of itself. Like the other senses, taste needs some kind of medium, since food needs to be in contact with moisture before it can be tasted. A completely dry tongue touching a dry object would not taste any flavor.

The Sense of Touch

The sense of touch is the most basic of all senses, and all animals share in at least this sense. Touch has many objects: hot and cold, moist and dry, hard and soft, rough and smooth.⁴⁰ Because of these many contrarieties, it is reasonable to conclude that touch is in fact multiple senses, but since the organs and medium are so closely related, it is difficult to distinguish them from one another. Aristotle argues that, contrary to first appearances, touch has a medium like the other senses. This medium is the flesh of the one who senses. The organs of touch would then be embedded in the flesh (we would call them nerve endings today). Touch can be defined as the ability to sense what is hot and cold, moist and dry, hard and soft, rough and smooth.

Touch is especially the sense of certitude. When we want to make sure that we are awake, we say “pinch me,” or when we want to make sure something is not an illusion, we reach out to feel it (like a ruler which looks bent in water). This is why Jesus insisted that the apostles touch Him after the resurrection, so that they would be certain that He possessed a real body. Because of the great certitude of this sense, both Aristotle and Saint Thomas say that those who have a very refined sense of touch are more intelligent, since they combine both certitude and discrimination in a single sense.

The Order of the Five External Senses: Dignity vs. Necessity

Experience teaches that the five external senses have a determinate order, reflected in the chart below:

On the one hand, sight and hearing are more dignified, while, on the other hand, touch and taste are more necessary. We say that touch and taste are more necessary since they are the senses most of all used in preserving the animal in being, and since they have more to do with the activities of the vegetative soul. Hot, cold, moist, and dry are qualities especially important to be aware of for maintaining both existence and obtaining nutrition. Sight and hearing are not as necessary for the being of an animal, but they are more important for the well-being of an animal. Hence, they have more to do with the activities of the rational soul.

Sight and hearing are more dignified for many reasons. First, they are less material than the other senses: hence, they have a certain affinity with reason, so that we typically name the activities of reason from these senses. For example, we say “I see” to signify that we understand. Second, greater distinction among things is made known through sight and hearing, so that more information and a greater penetration into reality is made possible through these senses. Finally, it is through these senses that beauty is most of all perceived.

While sight seems to be more dignified than hearing, still hearing is more important for learning. Therefore, those who are born deaf are greatly impeded in learning, while those born blind are not as greatly impeded, since man naturally learns through words.

Summary

• The five external senses are sight, hearing, smell, taste, and touch.

• Each of the five senses has a proper object and requires a medium through which sensation takes place.

• The qualities we perceive by means of these senses are really features of bodies outside of us.

• We cannot deny our pre-scientific understanding of the objects we sense since all further knowledge we might have of them depends upon this first understanding.

• Sight and hearing are the most dignified senses, and closest to reason, while touch and taste are the most necessary for life and closer to the vegetative power.

_______________

³⁴ Perhaps there are also other senses besides these five. One striking example is the sense which homing pigeons seem to have for detecting the magnetic field of the earth. When scientists placed an electromagnet on the base of their heads, these pigeons, which normally find their way home with ease, became disoriented and lost their way home.

³⁵ By the way, this answers the age-old question: if a tree falls in the forest and no one hears it, did it make a sound? The answer is, the exact same physical reality which we call sound would exist, but if there is nothing capable of hearing anywhere in the universe, you would not call it a sound. On the other hand, if there just happens not to be a hearer within earshot of the falling tree, then you would say it was a sound that was not actually heard.

³⁶ Supplementary text: Christopher A. DeCaen, “The Viability of Aristotelian-Thomistic Color Realism,” The Thomist 65, no. 2 (April 2001): 179–222.

³⁷ Imagine a scientist reasoning while assuming that contradictories are both true: “light has momentum, so it’s a particle, which is just as true as the statement that light doesn’t have momentum and is not a particle.”

³⁸ This becomes even clearer in the case of colored light (i.e., non-white light). If a room has a white wall and a green wall, but only a red light is shining in the room, the white wall will look red, while the green wall will look black. Red light only has a limited power to actualize the transparency of the medium: it makes the air actually transparent only for the color red. Since the color white contains the color red (as a kind of potential whole) the white wall looks red (that’s the only part of the white that can be seen through the air). But since the color green does not contain any red, no color at all can be seen on the wall, so it looks dark (black).

³⁹ We do not intend to discount the important and scientific contributions of the experimental sciences in clarifying our understanding of basic experiences like color and light. For example, it has been demonstrated through experiment that light travels at a very fast speed, not noticeable by the naked eye. What we must insist upon, however, is that experimental science should not conclude too much in claiming to overturn our basic, pre-scientific experiences upon which the science itself must be founded (which it will never do so long as the reasoning used is sound).

⁴⁰ Some would add pleasure and pain, but in fact, all senses involve pleasure and pain, though not as intensely as the sense of touch. Pleasure and pain are more modes of the objects of sensation than the objects themselves.

CHAPTER 8

The Internal Senses

Sense knowledge is not limited to what we perceive through the five external senses. Our experience manifests that we have other senses distinct from the five external senses. For example, we feel our emotions and are aware of the activity of sensation going on within us; we dream; we are sensibly aware of our own existence and substantial unity and even that of other animals; we have a sense, an instinct if you will, of what will be useful or harmful to us, and so on. These other sense experiences cannot be accounted for merely by the five external senses, and they differ from these external senses in many ways. Therefore, there must be, in addition to our five external senses, one or more internal senses responsible for these further sense experiences.

We note that when we speak about these internal senses, sensation means something different, but analogous to, what we defined as sensation in the last chapter. First of all, these other kinds of perception seem to have a broader object than the affective qualities of external bodies (for example, we can perceive fear and joy, which are not affective qualities). Moreover, they are less dependent upon things external to us, and they are less bound up with the here and now (for example, I can imagine things from the past and from far away). Nevertheless, these experiences are in many ways like the sensations we have through our external senses: they are of particular, individual experiences and are in some way derived from the external senses.

The Four Internal Senses

Aristotle identified four internal senses:

1. the common sense (or central sense);

2. the imagination;

3. the memory; and

4. the cogitative power (or estimative power).

Of these four, imagination and memory are most familiar to us, and their names form part of everyday language. The basis for the division of the internal senses into four is a two-fold distinction: first, the distinction between what is receptive and what is retentive; and second, the distinction between what is pleasant and what is useful. A perfect animal needs to perceive not only what is present, but also what is absent (otherwise it will not seek those absent things which are important for their well-being, such as prey and shelter). For example, a horse remembers where it can find shelter and water, even when it cannot sense those things with its external senses. Therefore, there must be a power of sensation which retains some perception so that the animal will be inclined to seek it in its absence. Moreover, a perfect animal needs to perceive not only what is pleasant or painful, but also what is useful or harmful (otherwise it will not be able to acquire things beneficial to it or avoid things harmful to it). For example, a salmon returns to its breeding ground not because this journey feels pleasant, but because it is perceived as useful. Similarly, a rabbit does not flee from a lynx because of the pain caused by seeing the lynx, but because it perceives the lynx as harmful. Based upon these two distinctions, a four-fold division arises which delineates the four internal senses as illustrated in the table below:

| Receptive | Retentive
Pleasant/Painful | Central Sense | Imagination
Useful/Harmful | Cogitative Power | Memory

What does each of these powers do?

The central sense receives what is sensibly pleasant or painful when such experiences are present. The imagination retains these sense experiences, making it possible to consider or perceive them when they are absent. The cogitative power receives useful or harmful experiences when they are present. The memory retains these same experiences when they are absent.⁴¹ The way in which the cogitative power (sometimes called instinct) and memory are about the useful and harmful may not be obvious. But notice that both of these powers pertain to things that are not causing pain or pleasure in the present. They perceive, together with a present sense experience, something else about the sensed object: something more than just how they are affecting you right now. A dog may have a memory of getting a treat when he fetches his master’s slippers. So he perceives, together with the slippers, a memory of something useful. A sheep may have never been attacked by a wolf and may not be experiencing pain from it at the moment, but the sheep perceives something together with the sensation of the wolf at a distance that alerts him to the fact that the wolf will be harmful.

The Common or Central Sense

The first and most basic of the four internal senses is the common or central sense. Because of the likelihood of confusion with the English colloquial expression “common sense,” meaning the ability to make sound judgments about ordinary matters, we will refer to this internal sense as the central sense for the remainder of the book.

The central sense is very close to the five external senses, and serves as a kind of gateway into the other internal senses. And since things which are close together are often confused, it is not at first obvious that there is a central sense besides the five external senses. Hence, unlike memory and imagination, the central sense does not have a common, often-used name in everyday speech.⁴² There are, however, two obvious aspects of our ordinary experience which manifest that there must be some central sense power which somehow unites the five external senses.

The first aspect of our experience is that we are sensibly aware of the differences between the various objects of our external senses. We are aware that white is not the same as sweet, that color is not flavor; yet we are also sensibly aware that we find both in the same subject, like sugar. Now sight cannot tell us that flavor is not color, since it has no knowledge of flavor at all. Nor can taste tell us that color is not flavor, since it has no knowledge of color at all. Only a sense power which knows both color and flavor can compare them. Our experience that white is sensibly different than sweet is therefore a certain indication of the existence of another sense power that knows both white and sweet, and this is the central sense.

The second aspect of our experience which alerts us to the existence of the central sense is that we perceive that we sense. I am sensibly aware that I am seeing and hearing, etc. Now it is not with my eyes that I perceive that I see. With my eyes I see color and light; I do not see my own seeing. Nor do I hear my hearing with my ears: I only hear sounds, and hearing is not a sound: it is the activity of sensing sound. Therefore, there must be some sense power which is responsible for my sensible awareness that I am using my external senses. In this way the central sense has as part of its object the activities of the five external senses. So the central sense can be defined as that receptive internal sense power which unites the external senses and by which an animal is aware of the activities of the external senses and can compare the objects of its external senses.

It might seem that it is impossible for a single sense power to be able to sense multiple kinds of sense objects at the same time, since it seems that the sense would be moved in opposed directions in the same moment. Aristotle gives an analogy to help us understand how the central sense can be one power yet share in many diverse powers. He says that just as five lines can converge in a single point, so the five external senses can unite in a single sense power.

If someone were to ask you to which line does that point of convergence belong, you could truly say that it belongs to each of them, depending which aspect you consider it to lie upon.

Like the external senses, the central sense is not subject to the will. So long as someone is awake and their external senses are presented with their proper object, the central sense will also be operating.⁴³

Imagination

The imagination is perhaps the best known of our internal senses. Our experience of dreams and our ability to form images and sounds in our soul at will without the presence of an external object (as when we imagine a picture before we paint it, or a note or tune before we sing it) are the clear evidence that we have an imagination. The ability to produce sense experiences in the absence of any external object is so unlike what we find in the external senses that the existence of imagination is obvious to all. In fact, this remarkable ability has even led some to doubt whether we are really sensing things outside of us when our external senses are at work; in some respect, then, imagination seems to be better known even than the external senses.

However, there are many experiences which manifest that the external senses cannot be reduced to imagination. First, unlike the external senses, the imagination can be exercised at will, even forming combinations not possible in nature. For this reason, the imagination can be considered true or false in some way, whereas the external sense cannot be other than true with respect to its proper object. Secondly, the intensity of the impressions from the imagination are much less than that found in the external senses, especially as regards pleasure and pain. Third, the voluntary exercise of imagination does not come with the conviction that the things imagined are real. A dreaming man may not realize that he is dreaming, but a man who is awake and using his external senses is sensibly aware and certain that he is not dreaming.⁴⁴

Memory

Memory is also a well-known internal sense. The memory retains sense experiences which were at some point in the imagination and external senses, and then represents them as past. This awareness of these experiences as having happened is what is most distinctive about memory, and allows us to distinguish easily the activity of the memory from the other internal senses. The apprehension of some sensible experience as past is not, in itself, received through the senses. However, it is an apprehension which is advantageous to the animal inasmuch as the animal is able to gauge in the present whether or not some sense experience similar to one in the past will be beneficial or harmful, as when a dog knows that a certain man is likely to feed him each day. Like imagination, memory is subject to reason in men, so that a healthy memory can call to mind a past sense experience at will.

We can define memory as the ability to make present in sensation some beneficial or harmful past experience in such a way that it is experienced as something from the past.

Besides sense memory, there is also intellectual memory. The intellectual memory differs from sense memory especially in two significant ways: intellectual memory calls to mind universals, and the universals brought to mind are a-temporal, not being associated with some particular time in the past.

Cogitative or Estimative Power

The cogitative or estimative power is the highest of the internal senses, and hence, the most like reason. In animals, this power is called the estimative power (which more or less corresponds to instinct in them), while in man, due to the special activities it performs in conjunction with reason, it is called the cogitative power (and sometimes it is even called particular reason). We shall principally be considering this power as it is found in man.

When an animal has some sense experience which it has never had before, it is the estimative power which apprehends how to act in that situation: for example, whether to pursue or avoid some other animal. The lamb knows instinctively to nurse and follow its mother; it also knows to flee from the wolf. To speak generally, the cogitative or estimative power correlates or associates individual sense experiences as they relate to what is helpful and harmful. By means of the cogitative or estimative power, animals and men sensibly apprehend individual substances as belonging to one species or another, but only as the term or beginning of an action or undergoing.⁴⁵ The estimative power does not know the individual precisely as an instance of a universal kind, for to know the universal is proper to reason. In animals, sense experiences that have no relation to the utility of its actions are not apprehended by instinct. Thus, a lizard does not flee from a lasso made from grass, since the lizard’s instinct does not apprehend grass as something to be fled.

We can define the estimative power as the ability to apprehend the utility or harmfulness of some present sense experience.

In man the cogitative power is subject to reason and able to be used as the instrument of reason. For example, the cogitative power is essential to forming inductions from sensible experiences. A slot machine discriminates between different values of coins, not because it knows what the kinds of coins are, but because it was designed by someone who does know what kinds of coins there are. Similarly, the cogitative power discriminates among different kinds of sense experiences and groups together similar sense experiences, not because it knows them as instances of a universal, but because it has a natural capacity to do so. In this way, the cogitative power gathers together and provides the matter upon which reason works to form an induction. Later on, once reason is more developed, it can command both the memory and the cogitative power to bring together certain experiences for the sake of forming new concepts. Since the cogitative power works so closely as an instrument of reason, it is sometimes called the particular reason (as opposed to universal reason).

The Importance of Imagination, Memory, and the Cogitative Power for Morality

Imagination, memory, and the cogitative power are all able to be trained by reason. If these powers are made subject and docile to reason, then they will be ordered in such a way to perceive and order sense experience correctly. But if emotion rather than reason is allowed to dominate over these powers, one’s perception of reality will be distorted. For example, sensible experiences that should be perceived as helpful, will be interpreted as harmful, and vice versa.

Summary

• The four internal senses are the central sense, imagination, memory, and the cogitative power.

• They are distinguished based upon what is received or retained, and what is experienced as pleasant/painful or useful/harmful.

• The central sense is closest to the external senses while the cogitative power is closest to reason.

• Imagination, memory, and the cogitative power are able to be used by reason and should therefore be trained by reason.

_______________

⁴¹ Supplementary text: Summa Theologiae, Ia, q.78, a.4.

⁴² In contrast, even something of the cogitative power also has a commonly used name in everyday speech: instinct.

⁴³ Supplementary text: De Anima, Bk. III, ch.1-2.

⁴⁴ Supplementary text: De Anima, Bk. III, ch.3.

⁴⁵ In fact, substance is sensed per se by the estimative and cogitative power, which is different from the external senses which only sense substance per accidens. But substance is sensed as an ultimate subject or underlying individual, not as that which answers the question “what is it?” Only reason understands substance in this latter sense (recall from the Categories that Aristotle distinguished these two senses of substance: ultimate subject and the “what it is” of a thing).

CHAPTER 9

The Rational Power

In plants we find the vegetative power, in animals both the vegetative and the sentient power, but in man alone do we find the rational power.⁴⁶ Among the ancient philosophers, few if any of the pre-Socratics were able to distinguish the rational power from the internal senses, and typically it was confused with imagination or some other internal sense. This is a sign that the rational power is less well known to us than the sentient power. Therefore, our first task will be to manifest that the rational power is really different from the internal senses and not reducible to them. After this, we will consider some properties of the rational power: for example, if it is able to act and exist apart from the body, if it is immortal, etc.

Distinguishing Reason from Sensation

Ordinary experience already indicates that thinking and imagining are significantly different. A simple experiment will help: close your eyes and imagine that you have won a $100 million lottery. How different would your experience have been if you thought you won the lottery? Again, imagine that there is a man outside the room with an automatic weapon who wants to shoot you. No matter how vivid your imagination is, your response is much different than if you thought there was a man outside trying to shoot you. What you think bears much more on reality than what you imagine, since the objects of thought are not just a product of our minds. Imagination just doesn’t have the power or the contact with reality that thought has.

So just a first consideration of imagination vs. thinking helps us to appreciate their difference. Let’s try to be even more precise in distinguishing reason from sensation. Recall that we must come to know the powers of the soul through their proper activities, and the activities in turn through their objects. Therefore, let’s look first at some differences between the objects of sensation and understanding, as indicated in the following convenient table:⁴⁷

Objects of Sensation | Objects of Imagination | Objects of Cogitative Power | Objects of Understanding
Cannot be sensed in absence of thing sensed. | Can be imagined in absence of thing imagined. | Can be considered in absence of thing considered. | Can be understood in absence of thing understood.
Thing sensed must be an existing thing. | Thing imagined need not exist. | Thing considered must exist. | Thing understood need not exist.
Thing sensed is neither true nor false. | Thing imagined is true or false only in some respect. | Thing considered is neither true nor false. | Thing understood (a statement) is true or false simply speaking.
An excessively sensible thing, such as very bright light, impairs sensation. | N/A | N/A | Something having an excess of intelligibility renders other things more intelligible.
Things sensed are particular. | Things imagined are particular. | Things considered are particular. | Things are understood universally: i.e., they are said of many things and understood to be in each of them.
Substance cannot be sensed. | Substance cannot be imagined. | Substance in the sense of ultimate subject can be considered. | Substance in the sense of “what something is” can be understood.
Relation cannot be sensed. | Relation cannot be imagined. | Relation as such cannot be considered, though this or that relation can. | Relation as such can be considered.
Opposites cannot be sensed together. | Opposites cannot be imagined together. | Opposites cannot be considered together. | Opposites can be understood together, like black/white, double/half.
Something sensed does not answer the question: “Why?” or “What?” | Something imagined does not answer the question: “Why?” or “What?” | Something considered does not answer the question: “Why?” or “What?” | Something understood does answer the question: “Why?” or “What?”

The above table reveals many differences between the objects of understanding and the objects of the external and internal senses. I have placed the objects which are proper to understanding in italics.

I want to comment briefly on two of these differences. First, only the understanding can grasp universals. If we reflect upon human knowledge, we observe a striking fact: human knowledge is divided into two very different kinds. On the one hand, what is particular and closer to the senses is best known to us. On the other hand, what is universal is best known to us. We know that man is an animal better than we know that man is a rational animal, and we know that man is a being better than we know that man is an animal. Being, the most universal conception, is best known to us, and we define everything else in terms of it. Compare this to the knowledge of animals: even very high primates who have been trained to use hundreds of signs to communicate are utterly incapable of forming or signifying a concept of being. For animals, the sensible particular is always better known.

Second, only reason can grasp relation as such. This means that only reason can grasp cause and effect as such, since both of these are kinds of relation. When animals seem to grasp cause and effect, they are merely making an association by means of their estimative power (instinct). Association allows one to call to mind things that have been experienced together in constant conjunction in the past. Thus, a dog remembers that it is hit every time it pees on the carpet, so eventually it associates peeing on the carpet with being hit, so it stops peeing on the carpet. The dog does not understand cause and effect as such or moral responsibility. It is one thing to associate A with B; it is quite another to grasp that A is the cause or effect of B.⁴⁸ Hence, no animal other than man is able to know and identify its own grandparents, since to know what a grandparent is, is to grasp the relationship of parent as such: a grandparent is defined as the parent of a parent.⁴⁹ Notice that while human beings are capable of perceiving causality, they can also make associations without necessarily considering causality. Most television commercials operate on this principle. They tend not to give reasons to buy their products, but rather they associate the product with something sensibly pleasant, like a beautiful girl or wealth or popularity. Men who are led in this way are no better than animals.

This ability to perceive relation as such seems to be at the root of all intelligence and the fundamental characteristic which defines intelligence. Universality and the capacity to grasp what a thing is both go back to the ability to grasp the determinate order or relationship between one thing and another. For example, I observe that a single nature is found in many individuals, so that one relation exists between that nature and those individuals. This unity of relation is what we call a universal. Hence, we can define intelligence as the ability to grasp order as such.

Intelligence and the Existence of God

Last quarter, when we were considering the proofs for the existence of God, we considered one proof that concluded that God was intelligent. However, at that time, we had not yet formulated a definition of intelligence. Now we are in a position to revisit that proof and see why the cause of the ordered universe must be an intelligent being.

Throughout the entire universe we find order; we find it in living things, in the motions and properties of matter, and in the laws of physics and chemistry, to name a few places. Besides this, the order found in the universe is inscribed in the very being of things (for example, gravity is a property of all bodies), and hence is not accidental to them. When things are in an order, there is some principle which gives them unity. An army is put in order by a general, and they are a single, ordered army when they can be reduced to a single principle, namely, the commander in chief. Now this kind of order must have an extrinsic and per se cause: for the things within such an order are themselves many, and yet order is a kind of unity. Now, things many and diverse in themselves cannot be the explanation of unity, for multitude and diversity are opposed to unity. In brief, the cause which explains some order cannot be a thing which is itself ordered. Therefore, there must be some cause of the order of the universe which is outside of the order of the universe.

A paradox arises here: how can something outside of an order cause that order? Nothing gives what it does not have. But whatever causes order gives order. Therefore, it follows that the cause of the order of the universe has the order of the universe. Yet at the same time, this cause stands outside of the order of the universe. From this it follows that the cause of the ordered universe has the order of the universe, but not as its own form: rather, it has it as the form of another. But to have the form of another thing as other is the very definition of knowledge. This means that the cause of the ordered universe must know order, and this is what we mean by intelligence. It follows that the cause of the ordered universe is an intelligent being.

A further difficulty arises here, however: sometimes a thing can cause some order without itself knowing that order as such. For example, a spider can weave an ordered web without knowing the order as such. The spider does not seem to have intelligence, even though it is a cause of some ordered thing. In response to this it should be appreciated that it is not necessary for that which is the cause of an ordered thing to know order as such, although it is necessary that it know the ordered thing. For example, the spider must have a kind of sense knowledge of the web it is weaving. On the other hand, the cause of the ordered universe as a whole not only causes an ordered thing, but also order itself, for it is the first and universal cause of all order. Thus, the cause of the ordered universe needs to know not only the ordered thing, which is the universe, but also the order itself. Thus, the first cause of the ordered universe must know order as such. And this is what we mean by an intelligent being.

Whether the Human Soul Can Subsist Apart from the Body

Up to this point in the course, we have examined the definition of the soul and its activities and powers. Having concluded that the soul is the substantial form of a living body (and therefore, that the soul is not itself a body), we are in a position to determine if the human soul is the kind of form which can exist apart from the body. For some forms do not subsist (that is, act and exist on their own) after separation from the body.

The key issue at stake here is whether or not it can be shown that the human soul is capable of exercising an activity which does not depend upon a bodily organ. Most living activities seem to depend upon a bodily organ. The eye is the organ of sight, the ear is the organ of hearing, the tongue is the organ of taste, and so on. Whenever sensation takes place, it is due to the reception of a sensible form in the sense organ; and even though this form is received in an immaterial way, a physical change of the sense organ is still necessary to produce these sensations. But if it can be shown that the human soul has some activity which is, of itself, exercised apart from the body, then it would follow that the human soul is capable of acting without the body. And if the human soul is capable of acting without the body, it must subsist after separation from the body.

The following syllogism is the basic proof for the immateriality of the rational soul:

1. A thing must lack what it is able to receive

2. But the human understanding is able to receive all material natures

3. Therefore, the human understanding must lack all material natures⁵⁰

The first premise is self-evident, and can be manifested by way of examples. If I am holding a book in my hand, I cannot receive that book, since I already have it. If I am wearing red glasses, I cannot tell whether a light has turned red or not. If my hand is a certain temperature, I cannot sense that temperature. In general, I can’t receive what I already have, since receiving something presupposes that I don’t yet have it.

The second premise is that the human understanding is able to receive all material natures. The first thing to see about this is that in understanding something, we must receive our knowledge of it from outside of us. Before we experience a tree or a dog or a triangle or anything else, we do not have a concept of these things. But after we have experienced these things, we are capable of forming a concept of each of them. Therefore, understanding, like sensing, always involves some kind of a reception of a form. In the case of sensing, this form is an accidental form, but in the case of understanding, we receive the very substance or “what it is to be” of the thing understood. So both sensation and understanding involve the reception of a form. Therefore, just as in the case of sensation, our understanding must lack the form it is to receive.

But what kinds of forms does the human understanding receive? The forms which we receive, we always receive through our senses. And therefore, the object of our understanding must be the forms of things which can be sensed or imagined: namely, the forms of material things. Therefore, the understanding must be lacking the forms of the material things which it receives.

Let us suppose for the sake of argument that our understanding is just like our power of sight. The power of sight is the form of the organ of sight, namely, the eye. In the same way, if our understanding were like our sight, our understanding would be the form of some physical organ like the brain, or some part of the brain. If this were so, our understanding would always have the form of that physical organ as its own form, and would be incapable of receiving that form. It would be like the aforementioned eye of a man with jaundice, which is incapable of sensing yellow because it is already yellow. Not only that, but the presence of one form would impede the understanding of other forms. A man with a yellow fluid in his eyes not only can’t sense yellow, but he can’t sense other colors rightly. Consider any material thing. If it has one form, it can’t have any others. A cow can’t be a horse so long as it’s a cow. A car can’t be a bicycle as long as it’s a car. In the same way, if the understanding always had the form of some material thing, it would be prevented from receiving the forms of other material things.

So far we have shown that if our understanding is to be capable of receiving the forms of any material thing, it must lack the form of any material thing. But it is clear that our understanding is able to know all material things. There is nothing which falls under our senses (i.e., no material thing) which we cannot understand, at least in a general way. This is shown by the fact that we consider the natures of all material bodies in natural philosophy, and are even capable of understanding them more particularly in the experimental sciences.

So we could reformulate the syllogism on the previous page as an if-then syllogism in this form: If A, then B; A is so, therefore B is so. If the human understanding is capable of receiving the form of any material thing (A), it must be lacking the form of any material thing (B); but the human understanding is capable of receiving the form of any material thing (A); therefore, the human understanding must be lacking the form of any material thing (B).

So our power of understanding does not have the form of any material thing as its own form. Therefore, when we understand something, this activity is not the activity of any bodily or material organ. And as we said above, if a part of our soul could be shown to have some activity which is independent of a bodily organ, it would follow that this part of the soul must be capable of existing apart from our body. Our conclusion is that the human soul is capable of existing apart from the body.⁵¹

Some Objections

One objection to the preceding argument is this: assuming that the human understanding has or uses a material nature to understand, how would we be aware that there is some nature which it is unable to understand? For example, the eye does not sense material natures which are transparent. Thus, it seems that the argument fails, since it assumes what it is trying to prove.

In response to this objection we note that even though the eye, for example, cannot sense the transparent, nevertheless we are aware of the existence of the transparent by means of some other sense, such as touch. In the same way, the understanding is not the only knowing faculty by which we can know material things. We can also sense material things. Thus, if there were some material nature which the human understanding could not understand, we would be aware of it through sensation: we would sense something and yet have no idea what it was. Yet there is no sensible thing in our experience which cannot be known by the human understanding. Therefore, the same conclusion follows.

A second objection is: the same thing can be possessed in one way and received in another. For example, as I am holding a book in my hand, the owner of the book can give it to me as a gift: I possessed it in one way (physically) and received it in another way (by ownership). Or again, I am a man and at the same time I can understand a man: I possess the form of humanity as my own form (naturally), but I receive it as the form of another (intentionally). In the same way, it seems that, if the human understanding had or operated through a material nature, it would be able to receive all material natures in a different way than it possesses its own material nature: it could possess a material nature as its own form, yet receive it as the form of another. Therefore, there is no reason why the human understanding could not have a material nature as its own form, and be able to receive all material natures as other.

To resolve this difficulty, it is necessary to reconsider why sense knowledge is impeded by the possession of a particular form possessed by the sense organ. For example, the hand cannot sense its own temperature, the eye cannot see the transparent, nor can it sense yellow in other things when it is itself yellow. Why must any part of the eye lack color? Although it needs to be able to receive colors, it receives them in a sensitive mode, “immaterially,” and not in the same way that bodies receive colors by alteration. And so, although something must lack whatever it is to receive, presumably nothing prevents it from both already having something and then receiving it, so long as it already has it in one way, and receives it in a new way. Similarly, nothing prevents me from knowing something and then learning it afterward, provided that the way that I already knew it is distinct from the way that I am about to come to know it. So it appears unnecessary for the eye to lack colors in a physical way, but it need only lack colors in an “intentional” way (i.e., the way in which it lacks the form of another as other). And yet we see that the eye does lack color also in a physical way, and when it does not (in those parts in which it is supposed to be receptive of color), this interferes with vision.

The reason is this: the eye, being a bodily organ, receives things in a “sensitive” form only by coming into contact with the natural presence of those things. So if colors were present in a natural way within the organ of the eye, precisely where it is to be sensitively receptive of color, it would either sense nothing at all (as when someone is asleep), or else always that color, and either nothing else, or at least that color would always be present and interfering with its reception of the colors of other things. Put another way, whenever the proper object of a sense organ is present, and the sense organ is active, that object will be sensed. So, if my eye always has present to it some physical color, it will always be sensing that color.

So too, then, if reason functioned in the mode of a sensitive organ, it would receive things in “intelligible” form only by coming into contact with the natural presence of those things. So if reason were a material organ, it would always be thinking about itself, or some part of itself, and either it would think of nothing else, or not without some interference—because exactly where it is supposed to receive things, the object (some part of itself, and its own nature) is present in precisely the way that objects are presented to it.

Having considered this, let us reconsider the definition of human knowing which we formulated before: the possession of the form of another thing, as other. Knowing is not just any kind of reception: it is the reception of the form of another thing. The argument we gave above for the immateriality of the human soul would fail if human knowing involved only the reception of a form in an immaterial way, but also essential to human knowing is the fact that it is the form of another thing. This part of the definition is essential to the notion of human knowing. In light of this, if we reexamine the objection given above, we see that the objection fails. If human understanding possessed a material nature as its own form, it could not receive that form in such a way that it is the form of another thing.

From this it follows that the human soul cannot know itself through itself. It can only know itself if it is somehow in another thing. And this is in fact the case: we do not know our own souls directly, but rather through reflection by considering its objects, activities, and powers. We know our soul through its effects which are other than the soul itself.⁵²

There remains a third objection: if our understanding is not dependent upon a material organ, why does a severe blow to the head make it impossible to understand? Or why does physical development of the brain go hand-in-hand with the development of mental capacity? Saint Thomas takes up a similar objection in the Summa Theologiae. In his reply to the third objection of Q.75, a.2, he says: “The body is necessary for the action of understanding not insofar as it is its organ of action, but as part of its object; for the image [in the imagination] is to the understanding as color is to sight.”⁵³ Recall that the object of our understanding is the form, or “what it is to be,” of material things which are sensed or imagined, just as the object of sight is the color of some object exterior to it. If I take away the exterior object of my sight (either by turning out the lights or removing all colored things from my view), this prevents me from seeing. In the same way, if I impede someone’s capacity to form images in his imagination (which does have a bodily organ), this will prevent me from understanding.

Other Arguments for the Human Soul’s Ability to Subsist

The conclusion that the activity of understanding is not an act of any material organ can be reached by a different middle term: every physical body is continuous. And whatever is received into a continuous thing is extended. For example, heat is in the different parts of a hot body, and color is in the various parts of a colored surface, etc. But the universal concepts of things which we understand are not extended in any way, for everything having extension is particular, while what is understood is universal. Therefore, the activity of understanding cannot be the act of a material body.

Again, a thing is known with certitude insofar as it is unchanging, for something which is always changing is true at one time and not true at another. But many things are understood with unchanging certitude, such as “man is an animal” and “every triangle has angles equal to two right angles.” These truths are true at all times. Now, all the particular things which we sense or imagine are always subject to change, since the organ of sensation is changeable. Therefore, the unchanging character of our knowledge must be due to the fact that our understanding is not the act of a changeable organ. But every material organ is changeable. Therefore, our understanding cannot be the act of a material organ.

Again, a material thing cannot receive opposite forms at the same time. The same part of a surface cannot be both hot and cold, or white and black. For this reason also, the eye cannot sense opposite colors in the same place, nor can the hand sense opposite temperatures in the same place. But the understanding can understand opposites through one another. For example, the concept of evil is understood through the concept of good, the concept of blindness is understood through the concept of sight, etc. Therefore, the act of the understanding cannot be the act of a material thing.⁵⁴

Can the Form of the Body also Exist apart from the Body?

The above arguments and responses positively demonstrate that the human soul is capable of existing apart from the human body. Yet this conclusion seems opposed to the definition of the soul which we gave earlier: the substantial form of a living body. How can something at once be a form and separable from that of which it is the form? The following objections and responses clear up the difficulty. First, read the objection, and then try to resolve it yourself in class. After you have discussed it and provided your own solution, read the response to see how it solves the objection. Four main problems occur in this regard:

(1) Form and matter are correlatives. But correlatives must exist together. Therefore, if the body ceases to exist, so also does the form of the body—that is, the soul.

Response: Things are relative either according to their very being (secundum esse), and such things cannot exist without their corresponding relative. But other things are said to be referred to another (relativa secundum dici), even though they are not relative in their very being, such as a head is said to be a head of a body and a part of a whole. It is in this way that the soul is related to the body.

(2) Substantial form is to matter as the shape of a statue is to the material of the statue. But if the material of a statue ceases to be, there can no longer be any shape. Therefore, the soul cannot exist apart from matter.

Response: Every likeness or analogy is the same in some respects and different in others. Otherwise, they would not be merely a likeness of analogy, but rather identically the same case. Substantial form is related to prime matter as the shape of a statue is to its material insofar as the shape of the statue is the principle by which the statue is said to be of such and such a kind. But unlike the relationship between accidental forms to their subjects (in which the subject gives being to the accidental form), the substantial form rather gives being to prime matter. Thus, being belongs first to the substantial form and second to the matter which it informs. Now, that which causes being in a thing need not cease to be when that in which being is caused ceases to be, since the posterior depends upon the prior, but not vice versa.

(3) In response to the answer given above, substantial form makes a thing to be what it is. But if that which is made to be what it is (i.e., the matter of the body) ceases to be, the soul ceases to be a substantial form (since it does not make anything to be what it is). Thus, the soul will not essentially be a form, so that the definition of soul is wrongly stated.⁵⁵

Response: Even after separation from the body, the soul retains its nature as something which is capable of and ordained to perfecting and informing a body, even though it is not actually perfecting and informing a body. Thus, the soul remains the same in itself although it happens that a body is not actually being informed by it. The soul remains a form virtually or in power.⁵⁶ Thus, it is not accidental to a soul that it be a form, whether or not it is actually informing a particular body, just as it is not accidental to color that it be visible, even though no one is actually seeing it.⁵⁷

(4) Things which have the exact same form are not distinguished from each other except by matter. But the soul after being separated from the body will no longer be individuated by its matter. Hence, it will be indistinguishable from all other souls, so that there will no longer be any individual souls, but only a single, separated human soul.

Response: The soul, although it has its individuality from the body, by coming to be in the body, does not require the body to remain individual after it is separated from the body. For insofar as the soul came to be in some particular body, and retains its relation to that body as something capable of informing and perfecting that particular body and only that body, each soul will be distinct from the other souls by the dispositions it acquired while it was in its own body. Just as wax before it is poured into a container is at first something indeterminate, but once it has acquired shape in the container, it acquires a determinate shape.⁵⁸

Whether the Human Soul is Immortal

It is one thing to say that a substance is immaterial, another to say that it is immortal: i.e., incapable of death. To be immortal, two criteria must be met:

1. a being must be alive and

2. the living being is of such a nature that its existence cannot be taken away from it.

It is obvious that the human soul is alive and exercises living activities. Moreover, it has already been demonstrated that the human soul is capable of exercising some living activities (such as understanding) apart from the body. The question remains: is the human soul of such a nature that its existence cannot be taken away from it?

To answer this question, we must return to the definition of soul: the substantial form of a natural, living body. Now, a substantial form is by definition “that which makes a thing to be what it is simply speaking.” The substantial form gives being to the composite, and in the case of the soul, that being is a kind of life. So it belongs to the very nature or definition of a substantial form to be that by which something exists. Since a form is that by which anything exists, it follows that the only way to take existence away from a thing is to take away its form. But a form cannot be taken away or separated from itself; it belongs to the very nature and definition of a form to be a form.

Therefore, if a form not only gives being to the composite, but also to itself, it would follow that such a form could not ever cease to exist. Now, substantial forms are of two kinds: some forms only cause existence in the composite, but other forms—namely, the human soul—not only cause existence in a composite but have existence in themselves, since they have an operation apart from the body and can exist apart from a body.

It follows that a substantial form which can exist apart from the body will always exist. Hence, the human soul is immortal.⁵⁹

Reincarnation?

If the human soul is both able to exist apart from the body and is also immortal, this raises the question of reincarnation. Could the same individual human soul return to another body? Many cultures and religions believe in reincarnation, some for philosophical reasons, others based upon faith or some extraordinary phenomena. Looking back at the principles we have established, we can demonstrate conclusively that reincarnation is impossible.

Reincarnation is the re-infusion of an already existing, individual soul into a new body different from its original body. Because of this, reincarnation is impossible. First, it is impossible for a human soul to enter into a body of a different species or genus (for example, a cow body or a tree). The reason can be seen from the definition of soul. Soul is the substantial form of a natural body. A substantial form makes the body it informs to be what it is. For example, the soul of a cow makes a cow to be the kind of animal it is, and the soul of a man makes a man to be the kind of animal he is (rational animal). Therefore, for a soul of one kind to inform a body of a different kind would result in a contradiction: the body would at the same time be the same kind as the soul (since the soul makes it to be that kind) and a different kind from the soul, since it was assumed that it was and remained a different kind of body from the original soul. For example, if a human soul entered a cow body, then the body would at the same time be a cow and a man: cow and not-cow; man and not-man.

It is also impossible for a human soul to be re-infused into a different individual human body from its original human body. For, if the soul is able to exist on its own apart from its original body (as happens with the human soul), then, when it is separated from its original body, either:

A) the separated soul remains a distinct individual from other souls of the same kind; or

B) the separated soul does not remain a distinct individual from other souls of the same kind (i.e., it is “absorbed” into a single, generic human soul which does not belong to this or that individual).

If (B) is true, then it would not be the same individual soul which enters into a new body, but simply a generic human soul.⁶⁰ So no one (no determinate, persisting individual) has been reincarnated. If (A) is true, then the individual soul would not be able to enter into a new body since it is “tailor made” for its original body. For the soul, having no matter itself, can only remain individual due to its determinate relationship with its original body. Hence, it would not be able to enter into any other body than its original body. But if this happened, it would be a resurrection, not a reincarnation.

Does the Human Soul Know Anything After Death?

So far we have shown that the human soul can exist apart from the body after death, and also that it naturally needs phantasms as an object in order to exercise its ability to know. We have also shown that the human soul can only be reunited with its own body and not some other body. From this it seems to follow that the human soul will not be able to exercise its knowledge (i.e., actually consider or know anything) so long as it is separated from its body. It seems that the soul separated from the body is like a sleeping man, unable to actualize its habitual knowledge.

This conclusion would follow if the separated human soul had to know in the same mode in which it knows when united to its body. However, if the soul is able to know in a different mode, a mode like that found in angelic beings, then the possibility of actual knowledge would still remain. This is the position which Saint Thomas proposes in his Disputed Questions on the Soul, something well worth reading for the interested student. However, a complete answer to this question, like the question of the resurrection of the body, is beyond philosophy. Some revelation is required to determine the exact extent of human knowledge when the soul is separated from its body. Once again, the theologian must take over where the philosopher must remain silent.

Summary

• The rational power is really distinct from the internal senses, and its activities cannot be reduced to sense activities because its object is essentially different than the object of any sense power.

• The intellectual power can be defined as the ability to know order as such.

• The rational power is distinguished from the intellectual power by adding the ability to come to know one truth from another truth.

• Because the human soul has an activity (understanding) which is not an activity in or through a bodily organ, the human soul can exist apart from the body, for what acts by itself exists by itself.

• The fact that the soul is a form does not prevent the soul from being able to exist apart from the body, since the being of the form does not depend upon the being of the body.

• The human soul is not only separable, but also immortal.

_______________

⁴⁶ Remember, all of this is spoken of in the context of natural philosophy, that is, the study of mobile being, which excludes any consideration of purely spiritual substances. Man is the only being with matter who is rational. Sometimes angels and even God are called rational, though, in its strictest sense, rationality implies reasoning from one thing to another. Therefore, it is a bit more precise to call angels and God intellectual beings.

⁴⁷ Understanding is taken broadly here to include the first two acts of reason: understanding what a thing is and understanding the true and the false.

⁴⁸ Animals might even be aware of a temporal priority between two things, but this is still not to grasp that the one which is prior in time is the cause. Before and after in time is distinct from before and after in being or causality.

⁴⁹ Animals can, by instinct, identify their parents, but they do not perceive them precisely as the cause of their being, but rather as the term of some action, like nursing.

⁵⁰ The middle term of this syllogism is “the human understanding is able to receive.” It could be put more formally as: the human understanding must lack what it is able to receive, but the human understanding is able to receive all material natures, therefore, the human understanding must lack all material natures. However, experience teaches that the above formulation is easier for most students to understand.

⁵¹ Supplementary text: Summa Theologiae, Ia, q.75, a.2.

⁵² This fact will become important when we consider subjectivism in the last chapter.

⁵³ ST, I, Q. 75, a.2.

⁵⁴ Supplementary text: A First Glance at St. Thomas Aquinas, Chapter 14, by R. McInerny.

⁵⁵ See Thomas Aquinas, Disputed Questions on the Soul, a.1., obj. 10.

⁵⁶ For a refresher on virtual presence, see Volume II: The Philosophy of Nature, chapter 6. Virtual existence is a kind of potential being: a potential being with some active power to produce certain effects or properties. Thus, something exists virtually when it is not actual, yet some of the effects which would naturally belong it are actually present. For example, the weight of the elements which compose the human body is present, even though the elements themselves are potentially present, not actually present.

⁵⁷ See Disputed Questions on the Soul, a.1, resp. 10.

⁵⁸ See Thomas Aquinas, Disputed Questions on Spiritual Creatures, a.9, resp. 2, 3, 4 &15.

⁵⁹ Supplementary text: Thomas Aquinas, Disputed Questions on the Soul, a.14, corpus.

⁶⁰ In fact, we have already seen that option (B) is false (see the answer to objection 4 above).

CHAPTER 10

The Agent and Possible Intellect

It is a fact of human experience that we go from a state of ignorance to knowledge. As small children we have very little knowledge, and what memories we have are vague. As we grow older, our knowledge grows and becomes more and more explicit. Thus, in human knowing, we move from a condition of potency (what Aristotle called a blank tablet) to a condition of actuality.⁶¹ Even in a given day we experience going from a state of not actually knowing or considering what we know to actually knowing or considering what we know. So this movement from potency to act is characteristic of human knowing.

What is the explanation for this change, and how does it come about? One thing is certain: it is through sense experience that we first begin to form universal concepts and ideas and to order our thoughts according to the order of our experiences. Aristotle called this process of pulling out universal concepts from particular sense experiences “abstraction.”

The Agent and Possible Intellectual Powers

To explain how we go from potency to act in our knowledge, it is necessary to posit both an active principle and a potential principle among our intellectual powers. Nothing moves from potency to act on its own, but only when some agent acts upon it.⁶² This shows that there must be some agent intellectual principle at work in human knowing. Not only that, but experience teaches us that it is within our own power to come to know new things. Therefore, this agent intellectual principle must be an intrinsic principle, a power belonging to each individual man. We will call this intrinsic active intellectual principle the “agent intellect.”

The agent intellect acts in such a way as to bring the potential principle in our intellectual power (the “possible intellect”) from a state of not actually knowing to a state of actually knowing.⁶³ But how does it do this? By the mediation of images (also called “phantasms”) in our internal senses. An analogy will help here.

When a projector shines light upon a screen, the screen is blank, having a plain white surface. But once a slide with some image is interposed between the light and the screen, then the picture in the slide can be seen as an image on the screen. The screen is no longer blank but contains some image. In this analogy, the light of the projector is like the agent intellect, the screen is like the possible intellect, the slide is like the phantasm in the internal senses, and the image on the screen is like the universal concept abstracted from the individual phantasm. The individual phantasm, being mixed up with and embedded in individuating conditions, is not of itself understandable (just as the image in a slide upon which no light is shining cannot be seen). But once the agent intellect acts upon it to abstract what is common from what is individual, the universal nature included in the phantasm can now be actually understood in the possible intellect. This is represented in the schematic below:

Before any image is present in the internal senses, the agent intellect contains virtually all universal concepts, but does not actually have any one of them. It is like a potential whole which contains many things in its power, like white light which virtually contains many colors, but does not actually have any one of them until passed through a prism.⁶⁴ That is why we do not actually form concepts of natural things until those natural things have been presented to our senses. Therefore, nothing is in the intellect which has not first passed through the senses.

Summary

• The rational soul includes an active and a potential power, called the agent intellect and the possible intellect.

• We reason to the existence of these two powers from the fact that we move from potency to act in our knowledge.

• We know the agent intellect must be a power intrinsic to each man because he is able to exercise it at will.

_______________

⁶¹ See De Anima, Book III, chap. 4.

⁶² Recall that this was demonstrated in natural philosophy when we considered the definition of motion; if needed, the discussion of this can be found in chapter 4 of Natural Philosophy.

⁶³ Remember that the “agent intellect” and the “possible intellect” are not two intellects within the rational soul, but are principles of the rational soul. There is only one intellect as such—these two, the agent intellect and the possible intellect, are powers of the intellect.

⁶⁴ See Disputed Questions on the Soul, a.5, resp.6.

CHAPTER 11

The Sense Appetite and
Rational Appetite

Both the sentient and rational powers of the soul discussed above are knowing powers which involve taking in or receiving things from outside of us. They are passive powers that do not, of themselves, cause us to move toward any goal. Yet it is an undeniable fact that sometimes we are inclined or moved from within toward some goal. When we acquire some new knowledge, whether it be sense knowledge of something particular or intellectual knowledge of something universal, this new knowledge brings with it the possibility of being inclined toward or away from something based upon that knowledge. When I smell pizza, there arises an inclination toward pizza. When I see a mountain lion, there arises an inclination away from the mountain lion. When I know that animals and plants act intelligently, but not from themselves, there arises an inclination to know why and how this can be so. Therefore, we must posit that, in addition to these knowing powers in the sentient and the rational soul, there must also be powers which incline and move us toward some goal. We call these powers the sense and rational appetites.

The Sense Appetite

Wherever we find sensation, we also find a sense appetite. The evidence for this is that in all things that sense, there is pleasure and pain. When an animal experiences pleasure, it continues to move or at least be inclined towards the object causing the pleasure. Similarly, when an animal experiences pain, it moves away or at least is inclined to move away from the object causing the pain. Sensation gives knowledge of some object, but pleasure and pain indicate whether or not the object is good for the animal. Therefore, the object of the sense appetite is the sensible good.

But doesn’t it sometimes happen that animals experience what is painful and still continue to act for some goal in spite of the pain associated with it? For example, when salmon swim upstream against the current for miles to return to their spawning ground, or when males fight over females, these animals are pursuing something involving pain. These facts force us to admit that there must be within the sense appetite two distinct principles inclining to two distinct objects: one inclination for acquiring what is agreeable and fleeing what is harmful; and a second inclination for resisting the things that prevent the acquiring of what is agreeable. The first inclination is called the concupiscible appetite and the second inclination is called the irascible appetite. For example, a lion may be seeking a mate for reproduction. He is acting according to his concupiscible appetite to acquire something pleasant and agreeable. But then he runs into another lion seeking the same female as a mate. So the two lions fight for the female. Here they are acting according to the irascible appetite to overcome an obstacle to mating.

Human beings also have these two principles in their sense appetite. These powers are exercised through various emotions. The emotions of the concupiscible appetite are love, hate, desire, aversion, joy, and sorrow. The emotions of the irascible appetite are hope, despair, fear, daring, and anger. The emotions of the irascible appetite all have objects involving some special difficulty. We will consider each of these emotions in detail when we consider ethics in the last quarter.

The Rational Appetite

Similar to the inclination arising from sense knowledge, there is an inclination arising from intellectual knowledge. Hence, there is a rational appetite besides the sense appetite. The rational appetite is called the will. The object of the rational appetite is not a sensible good, but rather a reasonable good. Even children recognize the difference between these two appetites when they make jokes like: “Do you love your ice cream?” “Yes.” “Well, why don’t you marry it?” Children see that the love for a sensible good like ice cream is essentially different from the love for a reasonable good like marriage, even though we give the same name “love” to our inclination toward both sensible and reasonable goods.

The will does not have a concupiscible part and an irascible part like the senses because the reasonable good is not particular and limited in the way that the sensible good is. Hence, reasonable goods do not come into opposition in the way that sensible goods do. However, it does often happen that a reasonable good comes into conflict with a sensible good. For example, the man who has diabetes sensibly desires the chocolate cake, even though he knows that it is not reasonable to eat it. The greater part of moral training involves bringing the sense appetite into conformity with the rational appetite. This is something very difficult for man, since man knows sensible goods better than he knows reasonable goods, even though reasonable goods are better for him than sensible goods. We will consider this more at length in our course on ethics next quarter.

Knowledge Is Before Appetite

Although the appetite is a mover in relation to the body and the other powers of the soul, it is itself moved by knowledge.⁶⁵ Unless something is in some way known, it will not be desired. Therefore, knowledge is before appetite, both in sensation and reason. By “before” we mean primarily in being and causality (the 2nd and 5th senses of “before” from the Categories), though sometimes knowledge is also before appetite in time.

Summary

• In addition to the knowing powers of the soul there are also appetitive powers whose proper object is some good.

• There are sense and rational appetites corresponding to sense and rational knowledge.

• The sense appetite has two principles: the concupiscible appetite and the irascible appetite.

• The rational appetite is a single principle which ought to rule over the sense appetite in man.

• Since nothing is desired unless it is known, knowledge is before appetite.

_______________

⁶⁵ The appetite moves the body and the other powers of the soul as an agent cause, but knowledge and the thing known moves the appetite as a final cause.

CHAPTER 12

Subjectivism

We end our consideration of the soul with a treatment of subjectivism and its related doctrines of relativism and skepticism.⁶⁶ These doctrines have become part of the intellectual custom of our culture. So true is this that in my experience as a teacher, I often find I do not have to give the students the arguments in favor of subjectivism or relativism or skepticism: they have heard the arguments over and over again from television, magazines, and books, as well as in school and from their friends. Modern students have been inundated with arguments for subjectivism since they were small children. We must treat these subjects not only because they are very common but also because they engender intellectual despair and destroy philosophy.

First let’s begin with some definitions of these terms. Subjectivism comes in two forms, one more radical than the other. I call the more radical position “hard” subjectivism and the less radical position “soft” subjectivism.

Soft Subjectivism: the position that we know our thoughts and sense impressions better than we know things.

Hard Subjectivism: the position that we only know our thoughts and sense impressions and we do not know things.

Intellectual Relativism: the position that there is no truth common to men, but only what is true for you and true for me.

Moral Relativism: The position that there is nothing objectively good, but only what is good for you and good for me.

Skepticism: The position that truth of any kind cannot be known.

These doctrines have a determinate relationship to one another. Soft Subjectivism leads to Hard Subjectivism, since once we admit that we know our subjective thoughts and sense impressions better than things, it is difficult or impossible to see how we can come to know things in themselves through our thoughts and sense impressions. Hard Subjectivism leads to Intellectual Relativism, since things in themselves, being unknown, can no longer be a source of common experience. Therefore, truth itself cannot be common among men, but only a private possession. This breeds Moral Relativism, since our determination of what is good depends upon what is true. Finally, Relativism leads to Skepticism since, if each man has his own truth, and men typically contradict each other, who is to say which is right. If each of these “truths” were indeed true, then we must conclude that truth contradicts truth. Thus, truth itself cannot be known.

Of these positions, Skepticism is the most radical and also the easiest to refute. To assert that truth cannot be known is to assert that something is true and that you know it. Imagine the following dialogue with a skeptic:

Joe Skeptic: There is no such thing as truth!

Ordinary Joe: Really, is that true?

Joe Skeptic: Well, maybe there is truth, but no one can know it!

Ordinary Joe: Do you know that that’s true?

Joe Skeptic: Well … no, I’m not sure if it’s true, but I’m sure that I don’t know if anything is true.

Ordinary Joe: So you know for certain that it’s true that you don’t know truth?

Joe Skeptic: Well … no, I just don’t feel certain that I know anything.

Ordinary Joe: So you admit that you don’t know anything! Therefore, you can’t teach me anything and I can’t learn anything from you, so you should stay quiet until you learn something.

So Skepticism is easy enough to refute. Relativism is also easy to refute, at least on a practical level. Imagine the following dialogue:

Joe Relativist: All truth and morality are relative. There’s no such thing as what’s objectively true and good. There’s only what’s good for me and good for you, so don’t try and impose your morality on me.

Ordinary Joe: What if harming you and your family seem good for me?

Joe Relativist: You can do what seems good for you so long as it doesn’t hurt anyone else.

Ordinary Joe: But then you are imposing your morality on me. If “do not hurt someone else” doesn’t seem good to me, how can you force your morality on me? You said there’s no such thing as what’s objectively true and good.

Joe Relativist: Maybe morality is objective if it involves me getting hurt.

Ordinary Joe: I thought so.

The truth is that if there is no objective standard of morality to which we are all bound, then the powerful will always get their way. If I want a piece of pizza, and someone else says he wants it, and there is just what seems good to each person, then the only way to resolve the problem is for each to try to get what he wants. So Moral Relativism is a doctrine which justifies the continued oppression of the weak by the strong. In fact, most people who say they are moral relativists are simply asserting that in order to justify their objectively bad actions. But as soon as any kind of injustice threatens them, they immediately become card-carrying moral objectivists. So while there are many who talk like moral relativists, no one is really a moral relativist in his heart; more often than not, Moral Relativism is used as a smoke screen to justify following emotions rather than reason.

Hard Subjectivism and Soft Subjectivism are more difficult to refute, especially Soft Subjectivism, since it makes more modest claims than the others. In fact, Hard Subjectivism, Relativism, and Skepticism would all be destroyed if Soft Subjectivism is shown to be false. Hence, we shall restrict ourselves to refuting Soft Subjectivism in this chapter. We begin by setting out two of the principal arguments for Subjectivism.

Arguments in Favor of Subjectivism

A First Argument for Subjectivism

The intellectual custom of our culture immerses young people in a subjectivist world view. Movies like The Matrix and Inception, among others, focus upon our apparent inability to distinguish dreams from our experience of reality when we are awake. Many philosophers had already formulated an argument for subjectivism based upon this and similar experiences centuries ago. Here is the argument:

A) Sometimes our experiences pertain only to things inside of us (such as dreams and phantom pains).

B) But these experiences seem to be the same as experiences we believe to be about things outside of us. This is clear from the fact that often we think that our dreams are about real things outside of us.

C) Therefore, it is more reasonable to assume that all our experiences are actually about things within us, not about things outside of us.

The philosophers David Hume and René Descartes propose versions of this argument.

The table which we see seems to diminish as we remove farther from it; but the real table, which exists independent of us, suffers no alteration. It was, therefore, nothing but its image which was present to the mind.⁶⁷

As the same percepts which we have when awake may come to us when asleep without their being true, I decided to suppose that nothing that had ever entered my mind was more real than the illusions of my dreams.⁶⁸

But I had sometimes heard it said by people whose arm or leg had been amputated that it seemed to them that they still occasionally sensed pain in the very limb they had lost. Thus, even in my own case it did not seem to be entirely certain that some bodily member was causing me pain, even though I did sense pain in it.⁶⁹

Since we cannot distinguish between our internal experiences and the experiences we believe to be about things outside of us, there is no way to be certain that we have any knowledge of things outside of us. And since all our experiences must somehow occur within us, it is safer to assume that all of our experiences are in fact a knowledge only (or, at least, primarily) of things within us.

A Second Argument for Subjectivism

Another common argument in favor of subjectivism goes like this:

A) Things can only be known by means of thoughts and sense impressions.

B) But whenever one thing is known by means of another, the means are better known. For example, if a conclusion is known by means of premises, the premises must be better known than the conclusion.

C) Therefore, thoughts and sense impressions must be better known than things.

D) If this is so, we can never be entirely certain that the thoughts or sense impressions are accurate representations of the things outside of the mind.

E) Therefore, it is better to assert that we only know our thoughts and sense impressions.

Immanuel Kant argues in this way, as does George Berkeley:

If we regard outer appearances as representations produced in us by their objects, and if these objects can be things existing in themselves outside us, it is indeed impossible to see how we can come to know the existence of the objects otherwise than by inference from effect to cause. And this being so, it must always remain doubtful whether the cause in question be in us or outside of us.⁷⁰

Though it were possible that solid, figured, moveable substances may exist without the mind, corresponding to the ideas we have of bodies, yet how is it possible for us to know this? Either we must know it by sense or by reason. As for our senses, by them we have knowledge only of our sensations, ideas, or those things that are immediately perceived by all sense, call them what you will; but they do not inform us that things exist without the mind or unperceived like to those which are perceived.⁷¹

While these are not the only arguments in favor of subjectivism, they are the most common arguments, and most of the other arguments seem to reduce back to one of these two. Next, we shall consider a critique of these arguments.

Shortcomings of the Arguments for Subjectivism

Critique of the First Argument for Subjectivism

Before we attempt a logical analysis of the first argument for subjectivism, it is helpful to point out some obvious flaws. First of all, in each case, the argument presupposes that we know things and not just our thoughts or impressions of them, and this assumption that we know things is used as a key premise in each argument. For example, Hume asserts as part of his argument that “the real table, which exists independent of us, suffers no alteration.” How would he know this if he did not know things in themselves? Similarly, Descartes asserts as part of his argument from dreams that they happen “without their being true,” and in his argument about phantom pains, he takes for granted that he is certain that the limbs are actually missing. So all of these thinkers in some way presuppose that things in themselves can be known, and that this knowledge comes through our senses. When those who try to deny some truth inadvertently end up asserting it in the very arguments they are making to deny that truth, this is a sign that the truth is self-evident.

The reason why, for example, our visual impression of a table changes as we change our perspective is because vision not only informs us about the size and shape of some object, it also informs us about our relative distance and perspective from it. Therefore, it does not represent size and shape in one way, but together with those additional factors. Vision would be deceiving us if it represented a table five feet away as if it were 100 feet away, or vice versa. On the other hand, touch represents size and shape in only one way, since it happens by contact. Therefore, we know by touch that the table does not change size or shape even when our visual perspective changes.

As for those arguments taken from sleeping people or people with missing limbs, they do not produce certain or necessary conclusions about the exercise of the senses in a waking, healthy, sober man. All they succeed in showing is that we should not trust our senses if our sense organs are defective, or if we are asleep, or out of our minds. Such conclusions could certainly not be the basis for rejecting the ability of the senses to know things in every case.

Logical Analysis of the First Argument

We now turn to a logical analysis of the same argument. This argument from dreams and phantom pains is even difficult to put into a syllogism—already a sign that it is not a carefully formed argument. But if we did put it into a syllogism, the argument would look something like this:

All B is A

No B is C

No A is C

Where

A = Experiences about things we think are outside us.

B = Experiences of things within us (e.g., dreams).

C = Knowledge of things outside us.

So, all experiences of things within us are the same as experiences of things we think are outside us. But no experience of something within us is a knowledge of something outside of us. Therefore, no experience of things we think are outside us is a knowledge of things outside us.

Looking at this argument, we notice a flaw right away in the form. It is a third figure syllogism (since the middle term B is in the subject in both premises), and it has a universal conclusion. No valid third figure syllogism concludes to a universal conclusion. Only particular conclusions are possible in the third figure. So, right away, we know the conclusion doesn’t follow.

Secondly, the first premise is obviously false. It does not happen in all cases that we cannot distinguish our inner experiences from our experiences of things outside of us. This only happens in some cases. So, in order to be true, the first premise would have to be restated as a particular affirmative: some B is A. From this it only follows that some A is not C, that is, sometimes experiences about things we think are outside of us is not a knowledge of things outside of us. But that’s not a controversial conclusion; nor is that subjectivism.

Another way the argument might be presented is as follows:

A) If something is possible in some case, it is possible in all cases.

B) But some of our experiences which we believe to be about things outside of us are not knowledge about things outside of us.

C) Therefore, it is possible that all of the experiences which we believe to be about things outside of us are not knowledge of things outside of us.

There are two main flaws with this argument. The first flaw is the premise that “If something is possible in some cases, then it is possible in all cases.” This is an example of the fallacy of composition. A few examples will manifest the falsehood of this premise. It is possible in some cases that a number is even, but does that mean it is possible in all cases? No, not all numbers can be even. It is possible that in some cases a statement is false, but is that possible in all cases? No, some statements must be true, since the statement “all statements are false” contradicts itself. Even in a case where something is possible in any case, it does not follow that it is possible in every case. For example, it is possible for any material thing to cease to be, but that doesn’t mean it is possible for every material thing to cease to be, since the corruption of one material thing is always the generation of another one. And it is possible to divide a line anywhere, but it is impossible to divide it everywhere. So that is one major flaw in the argument.

The second main flaw is that the argument itself presupposes that one knows that there is a real distinction between experiences about things “inside” and “outside” the knower. But how could someone know that this is a real distinction unless he knows something outside of him by an experience? So this distinction between “inside and outside,” “reality and thought,” seems to have no meaning.⁷²

Finally, it is not true that one cannot distinguish between the experience of dreaming and the experiences we have while awake. As I have already pointed out, that might be true sometimes when someone is dreaming, drunk, or mad, but it is not true when they are awake, sober, and sane.

Critique of the Second Argument in Favor of Subjectivism

Recall that the second argument in favor of subjectivism went like this: things, if known at all, are known only by means of thoughts and sense impressions. But that by which something is known is itself better known. Therefore, thoughts and sense impressions are better known than things.

A first observation to make about this argument is that it assumes that we know by means of thoughts and sense impressions. While this is something taken for granted and commonplace, because we are used to hearing it, this statement is by no means self-evident. Ask a small child what a thought is. It is very likely they have no concept of a thought. But ask them what a tree or a dog is and they can answer, at least by pointing to one. The truth is that the only way we can come to know about the existence of our own thoughts and sense impressions is either by way of an argument or at least by way of some reflection which begins with things outside of ourselves. I could hardly have an experience of my experience of seeing white, unless I first saw white. So our thoughts and sense impressions are derivative or secondary elements in our knowledge and experience. Some kind of argument or justification needs to be made simply to prove that we have thoughts or sense impressions.

Secondly, to know A by means of B is not the same as knowing A by means of knowing B. Certainly this happens sometimes, as in the case of knowing a conclusion by means of knowing the premises. But in other cases this is manifestly not true. I see by means of my eyes, but I do not see by means of seeing my eyes. Saint Thomas makes this point concisely:

That by which we know as by an instrument must be more known to us, as we know conclusions by principles naturally known…But that by which we know as by the form of the knower need not be known…and so it is not necessary, in order for anyone to understand anything, that he know his own intellect or intellectual light by which he understands.⁷³

And so it is not necessary to know our own thoughts and sense impressions first and then reason to the things which are their objects, the way we reason from an effect to its cause. We have shown that the two principal arguments in favor of subjectivism have serious flaws. These flaws reveal that these arguments are neither necessary nor certain. We now turn to some positive arguments against subjectivism which reveal that subjectivism cannot be reconciled with our experience of knowing nor with the correct definition of knowledge.

Positive Arguments against Subjectivism

First, thoughts and sense impressions are always of things, but things are not of thoughts and sense impressions. For example, a thought is of a dog or of a triangle, but a triangle or a dog is not of a thought. Hence, we can know what a thing is without knowing what a thought or sense impression is, but we cannot know what a thought or sense impression is without knowing a thing. Hence, things must be better known than thoughts or sense impressions.

Second, a subjectivist cannot even say what he means by a thought or sense impression. He cannot define them in terms of thoughts and sense impressions, since this would be circular. He cannot define them in terms of things, since his position is that thoughts and sense impressions are better known than things (and the defining terms must be better known than the term defined), and he cannot even point to them, since they are not sensible.

Third, every sensation is a sensation of something. But it cannot be a sensation of something outside of us, since according to the subjectivist we cannot be sure that things outside of us exist. Therefore, every sensation must be of another sensation. But that sensation too will have to be of another sensation, and so on to infinity. Therefore, to sense anything would mean sensing an infinity of things, which is impossible.

These arguments and many others manifest that subjectivism (in its hard or soft forms) is not a tenable position.⁷⁴

Problems with Subjectivism

The primary problem with subjectivism is that it begins with a faulty definition of knowledge. Subjectivists assume that knowledge is only something in the knower, without seeing that part of its very definition is that it is something of another. Knowledge is the possession of the form of another thing, as other. Since they have used a false definition of knowledge, subjectivists have erred about what is known first.

The second main problem with subjectivism is that it assumes from the beginning that we can know our own power of knowing first. But this is impossible if our power of knowing is not directly knowable. In fact, we showed above that before we think about anything outside of us, our mind is in potency, and so is not directly knowable. Only when we have thought about a thing is our knowing power actualized so that it can be known by reflection. This is why we had to define all of the powers of the soul beginning with the object, then the activity, then the power last. The power can’t be known first, and that’s a fundamental fact of our experience.

This concludes our introduction to the study of the soul. What we have done is only a beginning, but I think it is a good beginning. Now that we know something about the nature of the human soul, about its powers and properties, we are in better a position to say what perfects man and makes a man good. This is the purpose of ethics.

Summary

• Soft Subjectivism: the position that we know our thoughts and sense impressions better than we know things.

• Hard Subjectivism: the position that we only know our thoughts and sense impressions and we do not know things.

• Intellectual Relativism: the position that there is no truth common to men, but only what is true for you and true for me.

• Moral Relativism: the position that there is nothing objectively good, but only what is good for you and good for me.

• Skepticism: the position that truth of any kind cannot be known.

• Soft Subjectivism leads to Hard Subjectivism; Hard Subjectivism leads to Intellectual Relativism, which then leads to Moral Relativism (also simply called “Relativism”). Finally, Relativism leads to Skepticism.

• Subjectivism’s primary problem comes from a faulty definition of knowledge as only something in the knower rather than something which is also of another.

• Thus, knowledge is the possession of the form of another thing, as other.

_______________

⁶⁶ I am indebted for much of this chapter to a thesis written by Michael Augros of Thomas Aquinas College entitled: “Subjectivism and the Internal Principles of Knowing,” April 12, 1992. A copy of this thesis is available through Thomas Aquinas College, Santa Paula, CA. Additionally, for an alternative introductory treatment, C.S. Lewis devotes much of Book I of Mere Christianity to the inherent problems in subjectivism.

⁶⁷ David Hume, An Inquiry Concerning Human Understanding ( Indianapolis: Bobbs-Merrill, 1980), p.161.

⁶⁸ René Descartes, Discourse on Method (New York: MacMillan, 1988), p. 24.

⁶⁹ René Descartes, Discourse on Method and Meditations on First Philosophy, trans. Donald A. Cress (Hackett Publishing Company, 1999).

⁷⁰ Immanuel Kant, Critique of Pure Reason (New York: St. Martin’s Press, 1965), p.347.

⁷¹ George Berkeley, A Treatise Concerning the Principles of Human Knowledge (Indianapolis: Bobbs-Merrill, 1985), para. 18.

⁷² Just as someone who says that quantity exists on its own without substance is not actually denying that the quantity exists without substance, but rather is asserting that quantity is substance (since the meaning of substance is what exists on its own), so also the person who denies that there is no reality outside the mind of the knower is not denying that reality exists, he is asserting that his thoughts are reality. Thus, this form of subjectivism does not deny objective reality; it simply asserts that this objective reality is caused by the knower himself. That is, the knower is the source of all being: a strange position to try to reconcile with experience.

⁷³ Thomas Aquinas, Quaestiones Quodlibetales, Quodlibetal X, Question IV, a.1, ad.2.

⁷⁴ For those who would like to have a more complete refutation of subjectivism, I recommend the thesis by Michael Augros, cited above.