Abstract

The central question in Aristotle' Metaphysics Zeta- Eta is "What is substance?" and Aristotle answers that substance is essence or substantial form. But it is not clear what in Zeta-Eta Aristotle is inquiring and what the conclusion implies. ;In this study I argue that in Zeta-Eta Aristotle advances a new theory of substance: he establishes a new criterion for substance and identifies substantial form as primary substance. ;The criteria for substance which I take Aristotle to offer are these two. A thing is a substance if and only if its formula of essence is a definition. A thing is a substance if and only if it has no cause other than itself. The former criterion is derived from a consideration of essence and substance from the formulaic point of view, while the latter is derived from a consideration of essence and substance from the metaphysical point of view. ;However, Aristotle recognizes a problem in the logical or formulaic criterion. The difficulty is that the definition of substantial form doesn't seem to be different from the definition of a concrete particular in the composite structure of the formula. The definitions of substantial form and a concrete particular are all composed of parts. I claim that such dissatisfaction with the logical criterion is the main reason why Aristotle declares a new beginning in Zeta 17. ;In Zeta 17 Aristotle claims that it is impossible to identify the cause of the being of substantial form in the same way as the cause of the being of a concrete particular, since the thing asked about is ontologically simple. The cause of the being of a simple thing is itself. Aristotle claims that substantial form, which is the cause of the being of a concrete particular, does not have any cause other than itself. Substantial form is, therefore, primary substance on the metaphysical criterion. ;This interpretation implies that a concrete particular is not to be ranked as primary substance and that this revision can be taken as "a return to, or a renewal of sympathy with, Plato" as G. E. L. Owen described.