If we consider the traditional, Scholastic classification of the speculative sciences, it seems rather obvious that first philosophy, or metaphysics, has little to do with matter or with material beings, and has much to do, or has only to do, with beings separate from matter and motion. This is explicitly affirmed by many medieval masters, including Thomas Aquinas. Yet, if the medieval masters generally agree on the fact that metaphysics concerns what is immaterial, they disagree about the proper subject of metaphysics, i.e., the question of whether it coincides with God and other separate substances or with being qua being. This alternative is rooted in Aristotle himself, for his ‘first philosophy’ has at least a twofold structure: on the one hand, in Gamma, as is well-known, the subject of this science is identified with being qua being; on the other, for instance in E 1, the same science is called θεολογική: in other words, it is a theology (or ‘divine science’) which concerns what is separate from matter and motion (περὶ χωριστὰ καὶ ἀκίνητα). The history of the reception of Aristotle’s Metaphysics is above all the history of all the attempts – from the ancient commentators to Heidegger’s famous theses on the onto-theological constitution of Western metaphysics – to find a way to balance or to combine these two distinct subject-matters: being qua being and the divine. But how can a qualified subject (being qua immovable, eternal and immaterial, or being qua divine) coincide with an unqualified subject (being qua being)? Or, to reverse the question, how can being qua being exclude from itself material being, if matter is one of the principles which is included in the universality of being?

In the thirteenth century, Thomas Aquinas sought out a possible solution to this question, and found it in Avicenna. But while borrowing from Avicenna the essential part of the solution (i.e. the distinction between two different meanings of ‘immaterial’ and ‘immateriality’), some of his conclusions seem radically different from those of Avicenna. This is precisely the issue I would like to deal with today.

My presentation will consist of five parts. (i) I will briefly show how the question concerning the immateriality of the subject of metaphysics is raised in Aristotle and in his ancient commentators. (ii) I will explain the way in which Thomas Aquinas deals with this issue in his Commentary on the Metaphysics and, above all, in his Commentary on Boethius’ De trinitate, in which he introduces a distinction between two degrees of abstraction proper to physics and mathematics, and a further distinct operation, called separatio, proper to divine science. (iii) I will show how Aquinas draws this distinction from Avicenna, and yet distorts the intentions of Avicenna himself in order to reach a different and perhaps divergent conclusion. (iv) I will consider the main logical tool used by Avicenna in his re-interpretation of metaphysics and his criticism of Platonism: the distinction between plain negation and metathetic affirmation (or negation by equipollence). (v) I will briefly investigate the possible reasons for the peculiar attitude Aquinas adopts towards this issue, with respect to Avicenna’s legacy.