13 Why is form substance?
In claiming that form is substance, Aristotle relies on the connections between form, cause, essence and identity. He rejects the eliminative view (§8) that the so-called ‘coming-to-be’ or ‘perishing’ of an artefact or organism is simply an alteration of the matter. According to the eliminative view, this alteration does not involve the existence or non-existence of a distinct substance, any more than Socrates’ coming to be musical involves the existence of a distinct substance, musical Socrates. Aristotle replies that the production of an artefact and the generation of an organism introduce a new subject, a substance that is neither identical to nor wholly dependent on the matter that constitutes it
at a time. Although this statue of Pericles has come into being from a particular piece of bronze, we may repair the statue by replacing damaged bits; we preserve the same statue but we cause a different bit of bronze to constitute it. Similarly, an organism remains in
existence as long as it replaces its matter with new matter: it persists as long as its form persists (Generation and Corruption I 5).
When Aristotle speaks of the relation of form to matter, he may refer to either of two kinds of matter: (1) the proximate, organic matter (for example, the organs and limbs making up the organic body); and (2) the remote, non-organic matter (for example, blood, earth, water) of which the organic body is made. Remote matter can exist without the form of the organism, but the organism can persist without any particular piece of remote matter. Proximate matter cannot exist without the form (since it is the function of an arm or heart that makes it the limb or organ it is); the form is the actuality of which the proximate matter is the potentiality (On the Soul 412a10; Metaphysics 1038b6, 1042b10).
The role of the form in determining the persistence of an organism results from its role as the source of unity. The form, including the organism’s vital functions, makes a heap of material constituents into a single organism (Metaphysics VII 16). A collection of flesh and bones constitutes a single living organism in so far as it has the form of a man or a horse; the vital functions of the single organism are the final cause of the movements of the different parts. The organism remains in being through changes of matter, as long as it retains its formal, functional properties. Since the structure, behaviour and persistence of the organism must be understood by reference to its form, the form is irreducible to matter (see §9); the organism, defined by its form, must be treated as a subject in its own right, not simply as a heap of matter.
These facts about organisms explain why Aristotle sees a close connection between primary substance and form. Organisms are substances primarily because of their formal properties, not because of their material composition; hence we cannot identify all the basic subjects there are unless we recognize the reality of formal properties and of subjects that are essentially formal.
14 What are substantial forms?
The conclusion that primary substance and form are closely connected, however, explains only why some substances are essentially formal; it does not explain why form itself is substance. To explain this further claim, we need to decide whether Aristotle regards a substantial form as (1) a species form (shared by all members of a given species, for example, the form of man or horse), normally taken to be a universal, or as (2) a particular form, proprietary to (for example) Socrates. (See Metaphysics VII 10-16, XII 5, XIII 10, Generation of Animals IV 3 for important evidence.)
Some points favouring the ‘universal solution’ are the following. (1) Aristotle often contrasts the form with the compound of form and matter, and describes particulars as compounds; hence he apparently does not regard particulars as forms. (2) Similarly, he says that a particular differs from a universal in having both form and matter; hence no particular seems to be simply a form. (3) He says the form is what is specified in a definition, but there is no definition of a particular; hence a particular apparently cannot be a form. (4) He says that substance is prior in knowledge to non-substance, but scientific knowledge of particulars is impossible; hence they apparently cannot be substances, and only a universal can be a substance.
In favour of the ‘particular solution’ it may be argued: (1) a substance must be a subject, whereas all universals are said of subjects; (2) a substance must be a ‘this’, as opposed to a ‘such’, and hence, apparently, some sort of particular; (3) Aristotle argues at length that no universal can be a substance.
We might be tempted to conclude that Aristotle’s position is inconsistent. His conviction that substance as ‘this’ and substance as ‘what is it’ must be the same thing leads him to insist that the successful candidate for substance must satisfy the criteria for being both a this (a subject, and hence a particular) and an essence (a property, and hence a universal). If one and the same thing cannot satisfy both criteria, then no one thing can satisfy all Aristotle’s conditions for being a substance.
We need not draw this conclusion, however. We can maintain that Aristotle consistently favours the universal solution, if we can show: (1) a ‘this’ need not be a particular; (2) some universals are subjects; (3) a species form is not the sort of universal that cannot be a substance.
We can maintain that he consistently favours the particular solution, if we can show the following. (1) The contrast between form and matter does not imply that they are always mutually exclusive; some forms may be constituted by, or embodied in, particular bits of matter. Sometimes, indeed, Aristotle speaks as though a form is a subject that can persist
and perish and can exchange its matter. (2) The sense in which particulars do not allow definition and scientific knowledge does not prevent them from also being, in an appropriate sense, prior in definition and knowledge to universals (Metaphysics XIII 10 may attribute the relevant priority to particular substances).
These two solutions are different ways of expressing Aristotle’s belief that substances are basic. Both his metaphysics and his natural philosophy express and defend the conviction that natural organisms and their kinds are substances because they are fundamental; they are fundamental because they are irreducible to their constituent matter. It is more difficult to decide whether the individuals or their kinds are more fundamental. Perhaps, indeed, we ought not to decide; different things may be fundamental or irreducible in different ways.