Aristotle on Substance, Matter, and Form

1. Matter underlies and persists through substantial changes. A substance is generated (destroyed) by having matter take on (lose) form.
   1. A house is created when bricks, boards, etc., are put together according to a certain plan and arranged in a certain form. It is destroyed when the bricks, boards, etc., lose that form.

   2. An animal is generated when matter (contributed by the mother) combines with form (contributed by the father).

2. This suggests that the primary substances of the Categories, the individual plants and animals, are, when analyzed, actually compounds of form and matter. And in the Metaphysics, Aristotle suggests that a compound cannot be a substance (Z3, 1029a30).

3. This may seem a strange move for Aristotle to be making. But the idea may be this: a compound cannot be a basic ontological ingredient. Cf. these compounds:

              a brown horse
              a scholar
   

   Each of these is a compound of substance + attribute:
   
           a brown horse = a horse + brownness
           a scholar = a human + education
   

   In these cases, the compound is a compound of entities that are more basic. ("A scholar is not an ontologically basic item in the world -- a scholar is just a human with a liberal education.")

4. If then primary substance (in the Metaphysics conception of primary substance) cannot be a form-matter compound, what is primary substance? The possibilities seem to be: matter and form. (Aristotle actually discusses more possibilities -- this is a simplification.)

5. In Z3, Aristotle considers the claim of matter to be substance, and rejects it. Substance must be separable and a this something (usually translated, perhaps misleadingly, as "an individual").
   1. Separable: to be separable is to be nonparasitic. Qualities, and other non-substances of the Categories, are not separable. They only exist in substances. Separability, then, amounts to independent existence.

   2. This something: [there is much dispute over what Aristotle means by this odd locution] "Individual" comes close, except for the suggestion that only a primary substance of the Categories could count as a "this something". Perhaps an individual plant or animal counts as a this something, but perhaps other things do, too. For Aristotle seems to count form as, in some way, a this something (e.g., H1, 1042a28).  But, as a rough gloss, individuality seems to be what is at issue.

   3. Now it may seem puzzling that matter should be thought to fail the "separability/individuality" test. For:
      1. Separability: It seems that the matter of a compound is capable of existing separately from it. (The wood of which a tree is composed can continue to exist after the tree has ceased to exist.)

      2. Individuality: We can certainly pick out a definite, particular, batch of matter as a singular object of reference: "the quantity of wood of which this tree is composed at this time."

   4. But perhaps Aristotle's point is not that matter is neither separable nor individual; all he is committed to saying is that matter fails to be both separable and individual.
      1. Separability: Separate from a substance, matter fails to be a this. It owes what individuality it has to the substance it is the matter of. (What makes this quantity of wood one thing is that it is the wood composing this one tree.)

      2. Individuality: Considered as an individual (a "this something"), matter fails to be separate from substance. (This batch of wood no longer has any unity once it no longer composes the tree it used to be the matter of - unless it now happens to be the matter of some other substance that gives it its unity.)

6. So matter cannot simultaneously be both separable and individual, and therefore matter cannot be substance. The only remaining candidate for primary substance seems to be form (which Aristotle now begins to call essence).  It is clear that Aristotle is now focusing on the concept of the substance of something - i.e., what it is about an individual plant or animal (what the Categories called a "primary substance") that makes it a self-subsistent, independent, thing. Some evidence:
   1. Z.3, 1029a30: "the substance composed of both - I mean composed of the matter and the form - should be set aside … we must, then, consider the third type of substance [the form], since it is the most puzzling."

   2. Z.6, 1031a16: "a given thing seems to be nothing other than its own substance, and something's substance is said to be its essence."

   3. Z.11, 1037a6: "it is also clear that the soul is the primary substance, the body is matter, and man or animal is composed of the two as universal. As for Socrates or Coriscus, if <Socrates'> soul is also Socrates, he is spoken of in two ways; for some speak of him as soul, some as the compound."

   4. Z.17, 1041a9: "substance is some sort of principle and cause …"

7. Does Aristotle's view that substance is form or essence make him a Platonist? Most commentators think not, but for different reasons.
   1. Some think that the kind of essence or form that Aristotle counts as primary substance is one that is not in any way universal; a form that is as individual as the compound whose form it is. (Thus, Socrates and Callias would each have his own distinct individual form - there would be as many individual human forms as there are humans.)

   2. Others think that the "individual forms" solution is not to be found in Aristotle, and is anyway (for other reasons¹) unavailable to him. On their view, the primary substance of the Metaphysics is species form - something that is common to different members of the same species, but is still, in some plausible sense, an individual ("this something").

8. Z17 seems to chart a course about substance that is anti-Platonic but does not (so far as I can tell) decide between the individual-form and species-form interpretations of Aristotle's doctrine. The main ideas:
   1. The individual substances of the Categories are, indeed, compounds of matter and form, but

   2. They are not just heaps, or piles, of components.

   3. Rather, they're like syllables.

      That is, they're not just unstructured collections of elements, but have a structure that is essential to their being what they are. The syllables BA and AB are different, but they are the same collection of components - they have the same "matter".

   4. Structure or form is not just an ingredient (or what Aristotle here calls an "element") in the compound.

      [Aristotle offers an infinite regress argument for this: if the structure of a compound (e.g., a syllable) were just another component (along with the letters) then the whole compound would just be a heap. (E.g., the syllable BA would be a collection consisting of two letters and one structure. But a structure considered by itself, as an element, is not the structure of the syllable. The syllable BA consists of two elements structured in a certain way; it isn't an unstructured collection of three things, one of which is a thing called a structure.]

   5. So substance is the structure or form of a compound of matter and form (i.e., of a plant or an animal). At the end of Z.17, Aristotle describes substance, in this sense, in three ways:
      1. Primary cause of being.
      2. The nature (of a plant or animal).
      3. Not an element, but a principle.

9. The resulting view is not Platonism:
   1. The form that Aristotle says is primary substance is not, like Plato's, separable from all matter (except, perhaps, in thought). And it cannot exist if it is not the form of something. (E.g., the species-form does not exist if there are no specimens of that species.) But it is still separable, in Aristotle's sense, since it is non-parasitic: it does not depend for its existence on the particular batch of matter it's in, nor on the accidental characteristics of the compound it's the form of.

   2. The form is not a "thing", in the manner of a Platonic form. It's the way something is, the way the matter composing an individual compound is organized into a functioning whole.

10. Why doesn't this view collapse into materialism? That is, why isn't the form that can only exist in matter just a mode or modification of the matter that it in-forms? Why isn't matter more basic than form in the way that the primary substances of the Categories are more basic than their accidents?

    The substantial form (i.e., what makes Socrates human, or, for the proponent of individual forms, what makes Socrates Socrates) is really the basic entity that persists through change.

    This may seem wrong, since when Socrates dies, his matter persists, although he no longer exists.

    But: when we are tracing the history of Socrates through time, we do not follow the course of the matter that happens to compose his body at any given moment, but that of the form that the matter has. (Animals and plants metabolize; the matter that they are composed of differs from time to time.)

    So what makes Socrates the kind of thing he is, and what makes him remain, over time, the same thing of that kind, is the form that he continues to have.

    For Aristotle, the form of a compound substance is essential to it; its matter is accidental. (Socrates could have been composed of different matter from that of which he is actually composed.)

    Form may be accidental to the matter that it informs, but it is essential to the compound substance (i.e., the compound of matter and form) that it is the form of. Form is what makes the individual plants and animals what they are. Therefore, it is the substance of those individuals.

Notes

1.  Substances are supposed to be objects of knowledge, and objects of knowledge are universals, Aristotle says (417b21, 1140b31). Similarly, substances are supposed to be, par excellence, definable, and it is universals, rather than individuals, that are definable, according to Aristotle (90b4, 97b25, 1036a28, 1039b20, 1040a5).  These seem to be serious obstacles to the "individual form" interpretation.   Back to text.

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