3. Third Conclusion

224. Let the third conclusion be about the two actions contrary to the others [ nn.201, 212, instrumental or principal actions for substance], namely actions on the intellect and sense. I say that a separated accident (at any rate in the way that a quality of the third speciesThe reference is to the several species of quality listed by Aristotle, the third of which is the perceptible qualities that affect the several senses, Categories 8b26-10a11. ⁴⁷ is here separated, namely without a substance) can be the principle of both actions in the way it was before [sc. before when it existed in a substance, nn.194-195] - and this to the extent it is from itself (the reason for this addition will be plain in the solution of the following doubts [nn.230-238]).

225. I prove this as follows: in the case of any action of which some form is the total active principle, that form could, if it were to exist per se and in a manner fit for acting, be the principle of the same action; but quality is the total and formal principle of both the aforesaid actions [n.224], and when it is separated from substance, it is yet in quantity or, having extension as it is here [sc. in the Eucharist], it remains in a manner fit for acting, which is an extensive manner;     therefore etc     .

226. The major is plain, because when a total principle is in place and is under the idea under which it is of a nature to be principle, it can act as principle for that of which it is posited to be the principle.

227. The minor is proved in one way as follows, that nothing is taken away from this form by the fact that it exists per se save its subject; and the subject only makes a unity per accidens with it, but a per se principle of acting in a single order is a per se unity; therefore, the taking away of this subject takes nothing away from the per se principle of acting.

228. But this argument [n.227] only proves that the subject does not have the per se idea of principle in the same order as the accident; but there is no obstacle to prevent it being a per se principle of acting for the same action, yet in a different order (as is plain about ordered causes [cf. Lectura I d.3 n.372, II dd.34-37 nn.124-126]); and the per accidens unity of them [subject and accident] does not prevent unity of order.

229. Therefore the minor is proved in another way as follows: that form is the total principle of action which is the total principle of assimilating the passive object to itself - not only really, as in a real action, which is action on a contrary, but in intentional action, which is action on the senses. The first point is plain, because the formal term simply is like to the accidental form; therefore the accident can be the principle ‘by which’ of acting. The second point has a proof, because if the likeness in the senses falls away in some respect from the real likeness in the passive object [sc. the perceived object], then, on the part of this form as agent, it can as well be the total principle of this action as of the former; but if there is some further perfection in the sensation, this is not insofar as the sensation is from the sensible quality but insofar as it is from the sense power.