The unity of substantial form and definition: an interpretation of the argument of Aristotle’s Metaphysics Z12

FABIAN MIE

Ciudad de México

Conferencia; Conferencia sobre Aristóteleles; 2023

In Met. Z12, Aristotle raises a difficulty about the unity and composition of forms and their definitions (1037b11-14, b24-27). There are at least two main issues to be clarified in this chapter. (1) What is the announced relevance of this difficulty (1037b9-10), which is also said to be anchored to the discussion of the Analytics (APo. 2.6 92a27-33; and Int. 5, 17a13-15), for the theory of substance of book Z? (2) Aristotle seems to assume that a form is a unified compound made of purely formal parts, genus and differentia; but at the same time he rejects some other ways of explaining that unity. In fact, he argues that the unity of form can be explained neither (i) by being one thing predicated of another ―as an attribute that belongs to a subject is predicated of it― (1037b14-18) nor (ii) by participation ―as if the genus would take part in the opposite and the many differentiae (1037b18-24). But what is Aristotle’s own alternative in Z12? (3) His answer is presented in 1037b29 ff. I will claim that we can best understand his proposal by resorting to two formal features of division, which are made clear in Topics 6. First, the unity of forms is explained by entailment ―the differentiae entail the genus― (ἐπιφέρειν, Top. 6.6 144b16; συνεπιφέρειν, 144b17-18, b29-30), which is not something independent apart from the differentiae. Second, the unity of form is explained by proper differentiation, and so the many differentiae are reduced to the last one (διαιρῇ τῇ οἰκείᾳ διαιρέσει, 1038a24, and already 1038a9-10). As a result, we get a parsimonious and clear model of unity for complex forms, which can bound the highest (genus) and the lower (differentiae) formal parts together in just one determination: the last differentia, which is said to be the same as the form (1038a26). Moreover, this can shed light on the first question raised above. Since explaining the unity of forms turns out to be relevant for guaranteeing a main constraint on substance generally set in Z4.1030a3-7, i.e. that substances are definable essences with no different parts that would be externally linked by participation or by any other similar outer bond (1030a13-14). Thus, only Z12 can ground the claim of Z4 that there is no essence but of the forms (1030a11-13), which, in turn, fulfil a main condition (i.e. definability and unity) to make substantial forms into primary substance.