Aristotle on Substance, Matter, and Form
Matter underlies and persists through substantial changes. A substance is
generated (destroyed) by having matter take on (lose) form.
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.
An animal is generated when matter (contributed by the mother) combines with
form (contributed by the father).
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).
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
a brown horse
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.)
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.)
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).
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
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.
Now it may seem puzzling that matter should be thought to fail the
separability/individuality test. For:
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.)
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.
But perhaps Aristotles 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.
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
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
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:
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.
Z.6, 1031a16: a given thing seems to be nothing other than its own substance,
and somethings substance is said to be its essence.
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.
Z.17, 1041a9: substance is some sort of principle and cause
Does Aristotles view that substance is form or essence make
him a Platonist? Most commentators think not, but for different reasons.
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.)
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).
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 Aristotles doctrine. The main ideas:
The individual substances of the Categories are, indeed, compounds
of matter and form, but
They are not just heaps, or piles, of components.
Rather, theyre like syllables.
That is, theyre 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.
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 isnt an unstructured collection of three
things, one of which is a thing called a structure.]
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:
Primary cause of being.
The nature (of a plant or animal).
Not an element, but a principle.
The resulting view is not Platonism:
The form that Aristotle says is primary substance is not, like Platos, 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 Aristotles
sense, since it is non-parasitic: it does not depend for its existence on
the particular batch of matter its in, nor on the accidental characteristics
of the compound its the form of.
The form is not a thing, in the manner of a Platonic form. Its the
way something is, the way the matter composing an individual compound
is organized into a functioning whole.
Why doesnt this view collapse into materialism? That is, why isnt the form
that can only exist in matter just a mode or modification of
the matter that it in-forms? Why isnt matter more basic than form in the
way that the primary substances of the Categories are more basic than
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
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.
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.
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