Jacques Maritain Center : A First Glance at St. Thomas Aquinas / by Ralph McInerny


In his youth, Aristotle wrote with a kind of Platonic insouciance of a future life when the soul would be freed from the body and soar off to its appropriate sphere. With age came the realization that such claims are anything but self-evident. So too Thomas, as Christian believer, lives in the expectation of a life beyond this one where complete fulfillment can be had. But Thomas no more than Aristotle regards as self-evident the claim that the human soul can enjoy a separate existence. How could such a thing be shown to be true?

Capacities for Vital Acts

In speaking of the life-world, we inevitably refer to our own experience of life and eventually we come to see ourselves as a kind of summing up of the cosmos. A microcosmos, as the medieval liked to say. That man exhibits activities of a peculiar kind is true enough, but it is also true that all types of activities are found in him. He falls like a rock, but he also grows like a plant and senses like an animal.

The fact that we are a natural or physical thing among other natural things makes applicable to us that initial analysis of change and the features of what has come to be as the result of change. Like everything else, we are made up of matter and form. It is when we move off from this initial, extremely abstract level and analyze the kinds and species beneath its vast umbrella that we take note of the difference between living and nonliving substances.

Our own experience of life gets into the first account we gave of the soul: that whereby we primarily live, grow, sense, remember, dream, desire, and think. The soul is known from the activities of which it is the source and, because it must be the primary source -- living substances are not merely accidentally such -- the next account of soul, as the substantial form of a physically organized body potentially having life, has in the life-world an application as broad as matter-form has in the natural world.

If soul is known, not by direct intuition, but by way of vital activities -- seeing, hearing, hoping, etc. -- the soul being that in us which enables us to do such things, we nonetheless cannot identify the soul as such with any one of these capacities. The reason is obvious enough. We begin with the barefoot belief that hearing is one thing and seeing is another. The capacity to hear cannot be identical with the capacity to see. If they were, the initial distinction between them would be threatened.

What does happen, can happen. What actually occurs relates to potentiality. To be actual and to be potential are correlatives. Actual seeing relates to potential seeing, actual hearing to potential hearing. If the activities are different, the power to perform them must differ. And such powers or capacities or faculties must be distinguished from the soul itself. If this were not done, the capacity to see would be one with the capacity to hear and that would entail that seeing and hearing are identical. But if we know anything, we know seeing is not identical with hearing. So the soul must be distinguished from its powers and their acts.


Notice how oblique and indirect Thomas's talk of the soul is (talk he learned from Aristotle). There is no suggestion at all of taking a look inside and seeing the soul and that it is not identical with its powers and activities. That kind of introspection is worse than a parody of Aristotelian procedure. We begin with vital activities -- seeing, hearing, moving our hand, breathing out and breathing in -- that we are conscious of performing.

That they differ from one another is as certain as that they occur. It is when we observe that not everything in the physical universe exhibits these activities, that the distinction between the living and nonliving is made. The soul is introduced as the name for the peculiar kind of substantial form living substances have. The distinction of these activities from one another grounds the distinction of the powers from one another and mandates the distinction between the soul and its powers.

None of this relies on any special experience, none of it requires three credits in anything, none of it is "philosophical" or sophisticated. It is ordinary talk about ordinary certitudes. The initial analysis of these matters appeals to standards and principles of discussion everybody already possesses.

Layers of Life

Not only is there a variety of vital activities, they are ranked in terms of higher and lower. This may disturb your democratic impulses, but listen to the basis for the ranking.

Some vital activities are found in anything alive, some are found in fewer, and some are found only in man. The basis for the hierarchical arrangement is thus first of all how widely shared the activities are. Your worst fears of elitism are realized. What's wrong, I imagine you protesting, with being common and widely shared? And what's so special about being special? Man is the only species that starts forest fires but we don't pin a medal on him for that. There's another basis as well. Some vital acts are more distant from the kinds of activities any physical object can engage in, living or not, and that is the basis for saying they are more perfect. The more distant from purely natural activities, the more perfect vital activity is.

Sense Perception

The activities of the senses are analyzed on the model of change or becoming. We come to see such-and-such, we come to hear this-or-that. Just as Aristotle and Thomas argued from an analogy with accidental change to establish that the subject of substantial change had to be a non-substance (prime matter), so an analogy is established between physical change and coming to sense.

On the basis of this analogy, actual seeing is spoken of as the acquiring of a form, since all change results in a subject's having a new form. What is the subject of the change? The power of seeing. The eye? Not quite.

When I feel something, a physical change occurs in my body. If I touch something cold, my hand cools. If I touch something hot, my hand undergoes a physical change. While sensing is inconceivable apart from such changes, such changes are not what we mean by sensing. Why not? Because we do not say the poker with which we stir the fire feels the heart. We do not say the pot feels the soup. And so forth. But built into the account of sensation must be such physical changes. The hand acquires a new temperature, a new form. That is needed for touch but not equivalent to it.

Sensing is the reception of a form which does not result in a new instance of that form. The inventory of warm things is not increased when I perceive warmth, even though the changed temperature of my hand does add to that inventory. Paint a fence red and there is one more red thing in the world. Look at the red fence. Actually seeing it is a change from only potentially seeing it. Say that seeing is a reception of a form, red -- but there is not another instance of red in the world because of that.

The reception of a form in perception differs from the reception of a form in matter. When a form is received in matter there is a new instance of that form. When a form is received in perception, there is not a new instance of form. The form in perception is not received as form is received in matter.

This is the origin of talk of immateriality. That talk accelerates when we turn to the activity of mind.

Thinking of Things

However different the reception of form is in sense perception, sensation is well below thinking. It is in thinking that we have the reception of a form, thanks to which a group of things are the kinds of things they are, they are, that does not intrinsically involve the kind of physical change sensation does, when the physical organ of sense has to undergo a physical change.

The basic analogy with physical change is kept. Coming to know things is as a kind of becoming the reception of a form. The intellect is the subject of the change, the form is what makes a range of things be the kind of things they are. Because the physical change of an organ is not intrinsically involved, thinking is further removed from the physical change whereby new individuals of a species come into being. The form received by mind does not make the mind another instance of that form, as if thinking of what makes rhinoceroses to be rhinoceroses altered the thinker literally into a beast of that sort.

Mind more than sense is a subject of a kind of becoming in which a form is received in a way different from the way form is received in matter.

That is what is meant by speaking of mental activity as immaterial. Such talk emerges in a straightforward way from analyzing what everybody already knows. It does not rely on some introspective intuition whereby we surprise a spiritual realm within ourselves. To speak of the immateriality of thinking is simply to say that our grasp of that which makes things to be a given sort does not produce another instance of that sort. That is to say a lot, of course, but it is not a matter of slipping in the immaterial when nobody is looking.

The Remedy of Thinking

Because physical change results in singular and individual things -- this substance, this tan lady, that relocated pitchfork --the coming into being of one thing is the ceasing to be of another. Paleness has to go if I am to become tan; I can't be where I was if I am now here; the penalty of dieting is that I am no longer a pudgy 178. Unless the seed die, the plant cannot live.

In the physical world, things interact; there are causes and effects, indeed mutual causality is the mark of the physical realm. Things are ordered. But every thing is itself and not another thing, as Bishop Butler said. On several occasions, St. Thomas speaks of knowledge as a kind of remedy for the isolation of thing from thing. It is a way of being acted on which does not physically alter the recipient.

When I eat an apple, I have it in some sense, but of course the apple ceases to be. This does not happen when I look at the apple or smell it. Nor does it happen when I think of what it is that makes apples to be apples. To have the form of things in knowledge differs from having that form physically. We can have only one substantial form physically, but we can in principle know every kind of form there is. Thanks to knowledge, the whole universe can be writ small within our minds. Knowledge enables man to be a microcosm in a far more profound way.


Aristotle and Thomas pin their philosophical arguments that the human soul can exist independently of the body after death on the character of thinking. The nature of thinking lifts the human soul, although it is the substantial form of a living body, free from the confining and restricting consequences of matter.

It is not uncommon to think that a human person cannot simply fade into dust because of the character of those activities which mark off human from other natural entities. To have the capacity to think of galaxies and billions of years, to range over human history and the duration of our solar system, all this while sitting down, does not strike us as something that can be turned off like a light.

That hunch, if we have it, is what Aristotle and Thomas elaborate in their proof of the immortality of the human soul.

The upshot of that proof is for Aristotle puzzling and for Thomas dissatisfying. Aristotle almost never in his mature years talks about the soul after death. When he does, in the Nicomachean Ethics, the discussion seems fuzzy. The Christian belief in the resurrection of the body provides Thomas with a far richer conception of man's ultimate condition.

The nerve of the proof for the survivability of the soul is this. Thinking is an activity which does not intrinsically involve a bodily organ, and this provides the basis for saying that the soul whose power the mind is itself is capable of existing without matter.


Powers or Faculties of the Soul

I reply that it must be said that potency as potency is ordered to act so that a potency must be understood in terms of the act to which it is ordered and there will be a plurality of potencies insofar as there are diverse acts. Acts in turn are distinguished in terms of their objects. Every action is of either a passive or active potency and the object of a passive potency relates to its act as an efficient principle or cause: insofar as color moves sight it is the principle of seeing. The object of an active power relates to it as term and end: as the capacity of growth relates to an ideal size which is its goal. Action is the kind it is because of these, whether as principle or as end and term . . ..Potencies then are distinguished by their acts and objects.

The Remedy of Knowledge

Notice therefore that a thing is found to be perfected in two ways. First, according to the perfection of its existence, which belongs to it because of its proper species. But because the specific being of one thing is distinct from the specific being of another, therefore in any created thing having perfection of this kind there is lacking that much of absolute perfection as is found more perfectly in other species, such that the perfection anything has in itself is imperfect insofar as it is only a part of the total perfection of the universe which is arrived at by adding up the perfections scattered among things. Hence that there might be some remedy for this imperfection there is found another manner of perfection in created things, insofar as the perfection proper to another thing is found in it, and this is the perfection of the knower as knower. Insofar as something is known by a knower it exists in a certain manner within the knower, which is why in On the Soul Aristotle said that the soul is in a way all things because it is capable of knowing them all. In this way it is possible for the perfection of the whole universe to exist in one thing. Hence this is the ultimate perfection the soul can achieve, philosophers say, that in it the whole order of the universe, and its causes, be inscribed, and they assign this as man's ultimate end which according to us will consist in the vision of God since, as Gregory put it, "what will they not see who see the one who sees all?" The perfection of one thing cannot be in another in the determinate existence it has in the thing itself, so in order for it to be in another it must be considered without that which makes it determinate. And since the forms and perfections of things are determined by matter, something will be knowable to the degree that it is separated from matter, which is why that in which this perfection is thus received must itself be immaterial. For if it were material, the received perfection would be in it according to a determined mode of existence and would thus not be in it as knowable, namely, insofar as, being the perfection of one thing, it is capable of being in another. . ..Thus Averroes says in commenting on the De anima that the form is not received in the possible intellect in the same way as it received in prime matter; it is necessary that what is received in the knowing intellect be immaterial, and thus we see that according to the degrees of immateriality in things are there degrees of knowledge. Plants and the things below them can receive nothing immaterially and are wholly lacking in cognition. . ..The sense receives a species without matter yet with material conditions whereas the intellect receives them purified of material conditions. So too there is an order in knowable things. Material things, as Averroes says, are not intelligible unless we make them so, for they are intelligible in potency alone, but they are made actually intelligible by the light of the agent intellect, as colors becomes actually visible in the light of the sun. Immaterial things are intelligible in themselves, hence are of themselves more knowable, although less knowable to us. Therefore since God is the end of separation from matter, since he is completely free of all potentiality, he is both the highest knower and the most knowable reality.

-- Disputed Questions on Truth, Question 2, article 2.

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