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8 CONCERNING BEING AND ESSENCE priate to its essence. For by the form, which is the actuality of matter, matter is made being in act and a this somewhat. Whence that which is superadded does not give existence (essc) in act simply to matter, but existence in act of such sort as likewise accidents make, as for instance whiteness makes some- thing white in act. Wherefore whenever such form is acquired it is not said to be generated simply but in a certain respect (secundum quid). Hence it follows that in composite sub- stances the name of essence signifies that which is composed of matter and form. And this agrees also with the opinion of Boethius in his commentary Predicamentorum? where he says that ousia signifies a composite. For ousia according to the Greeks is the same as essence according to us, as Boethius him- self remarks in his book De Duabus Naturis. 10 Avicenna also says 11 that the quiddity of composite substances is itself a composition of matter and form. The Commentator also says concerning the seventh book of the Metaphysics 12 : "The na- ture which species have in things capable of generation is something intermediate that is composed of matter and form." Reason also accords with this, because the existence of a com- posite substance is not the existence of form only, nor the existence of matter only, but of the composite itself; and indeed essence is that according to which a thing is said to exist. Whence it follows that the essence by virtue of which a thing is called being is not form alone, nor matter alone, but both; although in its mode the form is the cause of its existence. We discover it indeed thus in other things which are constituted from more than one principle, since a thing is not named from one of those principles alone, but from that which unites both. 9 In Cat. I, De Substantia, PL, t. 64, col. 184 A. 10 DC Persona et Duabus, Nat, PL, t. 64, col. 1344 C. D. 11 Avicenna, Met, V, 5, f. 90 a F. 12 Averrocs, In Met, VII, c. 7, comm. 27, f. 83 a 41.