The Theory of Hylemorphism—Jonathan Dolhenty


A brief introduction to cosmology

Adapted from various sources and edited
by Jonathan Dolhenty, Ph.D.

Part Two:

The Theory of Hylemorphism

The term “hylemorphism” is made up of two Greek words, hyle “matter” and morphe “form,” and refers to the theory on the ultimate constitution of bodies as proposed by the Perennial Philosophy, that is, those who are within the tradition of Aristotle, Aquinas, and other commonsense philosophical realists. This theory holds that a body is composed of primal matter and substantial form. It is the theory first explained by Aristotle, four centuries before the birth of Christ, and it can be said that it stands miles above any alternative theory proposed since. For it meets the full problem it seeks to solve, and it offers a full solution.

The theory of hylemorphism is not revealed truth; it is not a theory that can claim divine authority. But it is a theory which, despite difficulties, has weathered the intellectual and experimental storms of nearly twenty-five hundred years, and is still the only rounded explanation of the nature of bodies that we possess. It has thus a sound claim upon the attention of our minds. It has a very strong case.

Yet there has been, among those not in the philosophical tradition of Aristotle, a marked tendency to condemn this theory without investigating it, and even some of those in the Aristotelian tradition have learned to speak of it with something of a cold and aloof manner. Even men who, in most of their philosophical work, merit our respect, stoop to the indecency and the dishonesty of condemning or ridiculing hylemorphism without having the slightest conception of what the theory actually teaches, or rather, with a totally wrong conception of what it teaches.


Now, there are two facts about any actual bodily substance that a philosophy of bodies must face and explain:

  • First: the bodily substance is a body. But it is more than that, for it is quite impossible for a body to exist without a specific determinant. We cannot say that a bodily substance actually exists as a body and nothing more; that it is no kind of bodily substance, but just pure body.
  • Second: it must be said about an actual body that it is a determinate specific or essential kind of body. In a word, some substantial principle must explain the bodiliness of a body; and some substantial principle, fused into substantial unity with the first, must explain the existing specific character of a body.

Hylemorphism calls the first of these principles primal matter or prime matter and the second of these principles substantial form.

Let us envision the favorite figure of of the old-fashioned novelist. Let us contemplate “the solitary horseman” riding between rows of trees along a rocky road. We shall not pause upon the romantic suggestions of the picture. We shall coldly reduce it to its elements for purposes of philosophical illustration. We shall consider these four things: the man, the horse, the trees, the rocks. Here we have four examples of bodily substance. And the first truth about them is that they are all bodies, one as much as another, one as truly and completely as another.

Yet, since we are not monists, we face the further fact that, although all these bodies are bodies, they are essentially or specifically different kinds of bodies. Each is a bodily substance; there is no mere accidental in their true bodiliness. Nor is there any mere accidental in their difference as bodily substances. For a substance that is living, like the tree, is substantially different from the substance which lacks life, like the rock. And a substance that has sentiency, like the horse, is substantially different from a non-sentient substance, like the tree. And, finally, a substance which has understanding and will (that is, rational life), is substantially different from a substance which lacks these perfections; so that the man and the horse are different by no mere accidental difference, but by a substantial difference.

The four bodies are all bodily substance, yet the four bodies differ from one another as substances. There must be, therefore, a dual substantial principle, or, more accurately, two substantially fused substantial principles in each of these bodies. For the four things are in agreement, they are at one as bodily substances, and, at the same time, they are not the same substance at all, but are substantially different.

  • There must be a substantial principle in each of the four which is the basis of its bodiliness; and,
  • There must be a substantial principle in each of the four which is the substantial determinant of the kind of substance that it is.

The first of these principles is prime matter; the second is substantial form.


Prime matter is the substantial principle found in all bodies. It is common to all bodies. It is the common substrate of all bodies. In point of prime matter, all bodies are at one. So far, monism is right; but monism goes calamitously wrong when it stops here. Prime matter is wholly without determinateness in itself. It cannot exist itself, for, as we have noticed, it is impossible for an existing body to be just a body and no more, that is, just a body, and not any kind of body.

Prime matter is substantial, but it is an incomplete substance; it requires another substantial thing to exist with it, or rather to give it existence in a determinate body. And this other substantial principle (unless it be a spiritual principle) requires prime matter to determine and make exist as a body; this other substantial is also an incomplete substance. Each leans on each, although the one (prime matter) is the determinable element, and the other (the substantial form) is the determining element.

Prime matter is called pure potentiality, that is, pure capacity for existence as a body. It is a capacity which must be filled up, determined, made into the only existible body (that is a specific kind of existing body) by a substantial principle other than itself. And, since the result of the union of this determining principle with prime matter is a single bodily substance, the union itself must be a substantial union, the substantial fusing of two substantial principles into an actuality which is a third thing, and not prime matter alone, not substantial form alone, but an existing body of a specific kind. This, of course, is perfectly in accord with our common sense, critically examined and expanded.

Prime matter then cannot exist itself, unformed. It does exist, but not alone. It exists as the common substrate of all existing bodies. It is that which makes any body a body; not actively, but by passively receiving the impress and union of the substantial form. For the whole character of prime matter is its passivity, its inertness, its indifference (or lack of tendency) to become this kind of body rather than another, in a word, its potentiality.


Substantial form, however, is active, determining. It makes the body actual (that is, an existing body) in a definite specific kind of actual bodiliness. The result of the substantial union of substantial form with prime matter is called second matter; and, of course, second matter means an existing bodily substance. Substantial form is the root and source of bodily actuality, of substantial determinateness, of activity. Prime matter is wholly potential, indeterminate, inactive or inert.

The theory of hylemorphism is not a mere clever invention. It is an explanation based upon the facts of a case. And the test of its value is the fact that it stands up. It has faced many difficulties. There are cases that seem to upset it. But careful investigation has always justified it.

The progress of experimental science, the splitting of the atom, the place and apparent power of one electron more or less in the constitution of a definite substance, — each of these facts, and others of like character, have seemed to some philosophers and to many scientists to be in conflict with the theory of hylemorphism. But it is not so.

There is no value in an argument of this sort: “If I knock out an electron of an atom of substance-A and find that I now have substance-B, it seems that these were basically one substance to start with.” The answer is that it seems nothing of the sort.

The difference is not a mere difference of accidental character because a number of like particles is an accidental thing in itself. For, although substances act upon one another through powers which are in themselves accidental, the activity is truly of substance upon substance. And if an electron more, or an electron less, should induce change, this may well be a substantial change. It may well be a change of structure unsuited to the enduring of a certain substantial form, which disappears in consequence; and the new structure receives simultaneously that substantial which it is suited to support. You change the substance of coal into a variety of substances loosely called “ashes and smoke” by applying the substance of fire. Yet this substantial change is affected by powers and capacities of the substances concerned, and these capacities and powers are, in themselves, as accidental as a mere numerical sum or numerical arrangement of electrons. The splitting of the atom, or the discovery of the character and function of electrons, is no more a new difficulty to the philosopher of bodily actuality than is the shoveling of coal on the furnace fire.

Indeed, if we shortsightedly declare that true substantial change does not occur, that all substances are the same determinate substance, we still must identify that substance as bodily (that is, as having prime matter) and as determinate in its kind of bodiliness (that is, as having substantial form). So hylemorphism stands in any case.

But to make all substances one substance is to fall into a self-contradictory theory called monism. It is to destroy the value of the theory itself which is proposed as true and certain, for if monism were true, human certitude would be bankrupt. By their fruits you shall know them; a theory which leads logically to skepticism or to monism or to both, is a theory that bears the evil fruits of falsity. The fact that there is an apparent difficulty on the side of sanity is surely no excuse for going insane. It is rather a strong challenge to the champions of sanity to study its resources more completely and apply its powers more thoroughly and astutely.

For, argue as you will, experiment as you choose, the fact remains and will ever remain that any bodily substance is bodily and is a certain specific kind. Any body has, of plain necessity, matter and form. If you consider the terms old-fashioned, you are privileged to invent more pleasing ones. But you cannot change facts by changing names.

There are persons indeed who say that there is no substantial change. Yet these persons would have a hard time proving their assertion, and the proof lies with them because they make the claim in the face of common human experience and of common human certitude. They have to prove a universal negative experimentally; any logician will be pleased to point out to them the difficulties of their situation.


The change from a living body to a corpse is indubitably a substantial change. For everything by which we identify the organic unity and the substantial character of the living body is not only changed by the thing called death, but all the processes once in possession and in operation are actually reversed. Instead of organic unity, we have (immediately upon death) a strong tendency to disunity and diversity; instead of a unified drive or tendency to vital function, we have the tendency to rest and equilibrium. In a word, by all the tests which distinguish one kind of body from another, the corpse is a radically different kind of thing from the living body. Substantial change is a fact. Another interesting example of substantial change is the change of bread and butter into the living flesh of the diner.

Now, if substantial change is a fact, it is an inexplicable fact unless two things are acknowledged:

  • The substances concerned (the substance changed, and the substance which is the result of change); and
  • Some substantial actuality which supports the change.

When food is digested, it is not a mere preliminary process which annihilates the food, a meaningless process which is unaccountably accompanied by the creation of blood cells. The ceasing of the food to be food is the emerging of the blood cells which came from the change of food. There is no annihilation (an abrupt and complete cessation of being) and a simultaneous creation (an abrupt and entire production out of nothing of a new being wholly unrelated to the other).

No, there is a substantial change of food into blood. Now, a change is a transit, a going-over. And a going-over requires a support which does not go over, but which is determined in bodily being first by one determinant, and, this giving way, by a new determinant which instantly takes the place of that which gives away. The support of substantial change is itself a substantial thing, and a substantial element of each of the two substantial bodily beings in turn. This support of substantial change is called prime matter; the substantial determinant which makes it one kind of body, and then the new substantial determinant which makes it another substantial body, is called, each in its turn, substantial form. Again, you may not like the terms matter and form, but you cannot deny the facts for which they stand. Substantial change is inexplicable without hylemorphism, although, as we say, you might like it under a more modern name, such as precipitation, or galvanization, or the etiology of substantial emergence.

We have said that there are four theories which propose themselves as fundamental philosophies of bodies, although three of them are not fundamental at all. All philosophies of bodies must, in last analysis, be resolved into one or other of these four forms. Now, we have found that three of these four theories are unacceptable, for they conflict with experience and are in themselves self-contradictory. Therefore, by exclusion, we prove the one acceptable theory to be the true theory. This is the theory of hylemorphism.

We stand, therefore, by the theory of hylemorphism. We defend it, not as partisans “taking sides,” but as philosophers, lovers of wisdom, seekers of truth. We refuse to leave what is manifestly reasonable, although sometimes difficult of application, in favor of what is manifestly unreasonable and often impossible of application. Hence our acceptance of hylemorphism is right and reasonable; it is worlds away from the stubborn business of taking sides in a free debate. In a word, we accept hylemorphism on evidence. Most of those who reject it do so by reason of mood, or temperament, or prejudice, or the desire to keep pace with the current scientistic fashion. It is not difficult to decide which of the parties stands on the more solid ground.

The late Dr. Jonathan Dolhenty was the Founder and President of The Center for Applied Philosophy and the Radical Academy, and is Honorary Philosophy Editor at Self-Educated American. Self-Educated American has adopted these projects beginning with a republishing and preserving of all of Dr. Dolhenty’s work.

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