 Clearly then, not only Avicenna’s ontology but also his henology should be understood in the light of the distinction between being and thing: the existent and the one are both primary indefinable concepts (Ilāhiyyāt, I, 5, 30, 3–4) and necessary concomitants of a thing (if a thing is, it is one), but being a thing is different from existing and being one: in itself the quiddity of a thing is neither existent nor one. Indeed, even unity is an attribute or a concomitant added to quiddity as it exists (Ilāhiyyāt, V, 1, 200, 13–201, 3; 201, 8–13). So, while for Aristotle “being” and “one” are coextensive—being one is a per se attribute of being—(they are not identical in meaning, although Aristotle presents this possibility: Metaph. 1003b25), for Avicenna being and one are per se attributes of a thing, so that being and one are coextensive, although not identical in meaning, and this is so whenever we can speak of a “thing” (Druart 2001; Wisnovsky 2003a, esp. 158–60) i.e., always excepting the Principle. Consequently there is the difficulty of conceiving “one” as both univocal and transcendental: being and being one coincide only because they are both said of every category and do not indicate a substance (Ilāhiyyāt, III, 2, 103, 7–9). Unity—which is an accident in the category of quantity—is indivisibility; it is said in terms of priority and posteriority—with a certain ambiguity or modulation (bi-l-taškīk)—of several things (Ilāhiyyāt, III, 2, 97, 4–5; 99, 13–14; but cf. Averroes on Aristotle’s Metaphysics, 39–42; Menn 2013) and cannot coincide with being because otherwise multiplicity could not be (unity and multiplicity—which derives from unity—cannot be opposite: Ilāhiyyāt, III, 3, 104, 6–7; 6, 129, 11–130, 7).