14. Explanation and Definition in ’ Commentary on ’s Metaphysics

Fabrizio Amerini

In his forty-year career, Sten Ebbesen has dealt with a great number of medieval topics, and metaphysics has not escaped his notice. In a series of texts that, in recent years, Sten has published in the Cahiers de l’Institut du Moyen-Âge Grec et and elsewhere, he has, among other things, directed the attention of scholars to the presence of sensitive logical and semantical issues in the commentary tradition on Aristotle’s Metaphysics.1 In this paper I want to continue this line of investigation and focus on the interconnection between logic and metaphysics. I will not, however, approach this issue from the usual perspective of the relation between these two sciences—their borders, methods and subject-matter. My con- cern, rather, is to discuss the contribution that (syllogistic) logic can give to metaphysics, that is, the role that it can play in a metaphysical explana- tion of natural phenomena. Since the medievals normally read Aristotle’s Metaphysics as a work applying the Posterior Analytics theory of science to the field of metaphysics, (syllogistic) logic is supposed to structure the way of doing investigation in metaphysics. An interesting example of such an interconnection is given by Metaphysics 7.17, the chapter where, according to some contemporary interpreters, Aristotle extends the Posterior Analy­ tics explanation theory from attributes to substances. The present paper deals with Thomas Aquinas’s interpretation of this chapter.

1 See, e.g., S. Ebbesen, ‘Words and Signification in 13th-Century Questions on Aristotle’s Metaphysics’, CIMAGL 71 (2000), 71–114, and S. Ebbesen, ‘Radulphus Brito on the Metaphys- ics’, in J. A. Aertsen, K. Emery, and A. Speer (eds.), Nach der Verurteilung von 1277: Philoso- phie und Theologie an der Universität von Paris im letzten Viertel des 13. Jahrhunderts (Berlin: De Gruyter, 2001), pp. 456–92 (repr. in S. Ebbesen, Collected Essays, 2 vols. (Aldershot/ Farnham: Ashgate, 2008–9), vol. 2, pp. 197–208). See also S. Ebbesen, ‘Five Parisian Sets of Questions on the Metaphysics from the 1270s to the ’, in F. Amerini and G. Galluzzo (eds.), A Companion to the Latin Medieval Commentaries on the Metaphysics (Leiden: Brill, forthcoming). 240 fabrizio amerini

Aquinas on the ‘Logical’ Character of Aristotle’s Examination of Substance in Metaphysics 7

At the beginning of his commentary on book seven of the Metaphysics, Aquinas notices the ‘affinity’ between logic and metaphysics. This is quite usual. The occasion is given by Aristotle’s claim that the examination of the notion of substance, understood as essence, will be first set forth in a logical way (λογικῶς, logice).2 It is not easy to establish what Aristotle pre- cisely meant by λογικῶς.3 What is certain, however, is that for many con- temporary interpreters Aristotle changes the way of scrutinizing substance not starting in book eight but from the last chapter of book seven. At the very beginning of 7.17, in fact, Aristotle states that he wants to approach afresh the question of substance: since substance is some sort of principle and cause, the examination of substance must, he claims, restart from this point.4 Aquinas regards such anticipation as unnecessary, for there is a point in 7.17 where Aristotle explicitly reconnects the examination of substance qua principle with the preceding examination of substance qua essence.5 For Aquinas, such a connection shows that in 7.17 Aristo- tle is continuing to investigate substance in a ‘logical way’. Moreover, since Aquinas links the ‘logical way’ with definition and predication, such a connection also shows that in 7.17 Aristotle aims to illustrate, in a very general way, in what sense essence and definition can be explanatory of a thing’s substantiality. Only with book eight does Aristotle come to the metaphysical investigation properly speaking, when he introduces the notions of form and matter into the analysis and accounts for them as metaphysical principles of a thing’s substantiality.6 Of course, this does not mean that in book seven Aristotle never mentions form and matter, but when he does, Aquinas explains, he is either anticipating what he will say in the subsequent book,7 or he is still scrutinizing matter and form in a

2 Aristotle, Metaphysics 7.4.1029b13. 3 For the state of discussion, see G. Galluzzo and M. Mariani, Aristotle’s Metaphysics, Book Zeta: The contemporary debate (Pisa: Scuola Normale Superiore, 2006). 4 Aristotle, Metaphysics 7.17.1041a6–7: ‘ἐπεὶ οὖν ἡ οὐσία ἀρχὴ καὶ αἰτία τις ἐστίν, ἐντεῦθεν μετιτέον’. 5 Aristotle, Metaphysics 7.17.1041a27–30. 6 Thomas Aquinas, In duodecim libros Metaphysicorum Aristotelis expositio 8, lect. 1, n. 1681 (ed. M. R. Cathala and R. M. Spiazzi (Turin and Rome: Marietti, 1950), p. 402). Henceforth, this commentary is referred to as Exp. Met. 7 See, e.g., Aquinas, Exp. Met. 7, lect. 11, n. 1536 (p. 370).