D. To the Fourth

303. As to the fourth argument [n.182] from the Metaphysics, it could be brought in for my side; because I concede that a quality cannot be the principle for generating a composite substance. But in another respect it is brought in against me, because neither is a quality the principle for generating a composite quality, nor would a substantial form (even if it existed per se) be a principle for generating a composite substance - which, however, you would have to deny, just as you also deny it about a quality and a composite quality [nn.182, 186].

304. Therefore, first I say to the authority [from the Metaphysics, n.182] that the Philosopher’s intention is that Plato’s ‘Idea’ cannot be a principle for generating a composite substance, because no completely immaterial substance can generate a composite substance without the mediation of a body [cf. Ord. II d.3 n.208].

305. But how is this proposition true with him [sc. Aristotle]?

I say that it is so because he posits the order of causes in the universe to be simply necessary; and he sees the separate substances, according to his own position, as moving the heavens, so that they produce, through such movement, other things down below; but they would not thus move if they could immediately produce them, because then the order of causes would not be necessary - which for him would be unacceptable.

306. And for this reason one ought not to impose on him the lies‘Trufa’, a medieval word for ‘truffle’ but also for untruths or lies. ⁵¹ of some people, that a separated substance could not cause anything here below because of an imperfection, either such or such in a separated substance, or because of the disproportion between a simple and a composite - but only that they could not do so because of the order of causes. For he conceded that a simple substance causes the moved heaven, which heaven is a per accidens composite. Why then is it thus not a per se composite, since the agent has no greater fit with a per accidens composite (either in whole or in part) than with a per se composite?

307. But we do not agree with the Philosopher in the proposition: ‘the order of causes is simply necessary’ [n.305]. For he would say that a simple accident would not produce a qualified subject - not because he would deny that a simple accident (when it is in a subject) is the whole idea of acting, and thus that, if it could exist per se, it could also act per se, but because he would deny (because of the necessity of the order of causes with him) that this could be the case.

308. But as to what is said there [n.182], that ‘a substantial form, if it existed per se, could not, according to this authority of the Philosopher, be the principle for generating a composite substance’, this indeed contains a doubt. For if it is the case that, just as a quality is the total principle for altering something, so the substantial form of the generator is the total principle for generating, the up shot for us is to say that a substantial form that is a per se being can generate a substance - save that it would not be in a suitable mode for acting (for nothing has a suitable mode for acting on a matter quantum unless it is itself a quantum - speaking of a univocal agent).

309. But on the question whether a substantial form alone could be the principle for generating, or (what is more) that the substance alone would be the principle for generating, look above in the first article [i.e. the solution of the question, nn.257-260].