Abstract
Aristotle claims in Metaphysics Z.17 that form is both a cause and principle of c‐substances. In this chapter, Wedin argues that the explanatory, or causal, role of form is in the background of the entire discussion, and indeed directs much of the argumentation of Metaphysics Zeta. Form is the cause of some matter being a unity and not a heap, because form alone explains how the material parts of a thing are united in a single whole. Wedin draws together the main results of the preceding investigation of Zeta—that form is essence, that form must not contain matter or actual parts, and that form must not be a certain kind of universal—and he argues that these constraints on form are designed to serve the explanatory role that Aristotle explicitly gives to form in Z.17. Wedin emphasizes that the notions isolated in the examination of the earlier chapters, such as the purity of form, weak proscription, and dual complexity, each contribute to the account of form as the explanatory principle of c‐substance.