Form and Function in Aristotle

On the one hand, Aristotle claims that the matter of a material thing is not part of its form. On the other hand, he suggests that the proper account of a natural thing must include a specification of the kind of matter in which it is realized. There are three possible strategies for dealing with this apparent tension. First, there may be two kinds of definition, so that the definition of the form of a thing does not include any specification of its matter, whereas the definition of a compound does. Second, the definition of a substance may not include a specification of its matter at all, but still reveal in what kinds of matter its form can be realized. Third, there may be a special kind of matter, functional matter, which belongs to the form of certain things. I will show that the functional matter of a thing does not belong to its form (in a strict sense of "form"), but that an adequate account of natural substances and their functions must nonetheless involve a reference to their functional matter. This means that the function of a natural thing is not the same as its form and that its adequate account as a natural thing is not a definition (in a strict sense of "form" and "definition").