Whereas this power, to wit the one that conceives mentally-grasped things, the more it perceives wearying mental conceptions the stronger it becomes for its work [the more efficient it becomes], wherefore it has no need for an instrument in its operation of perceiving, and hence it perceives of itself. Now, we have already shown that every power perceiving of its own self is an essence; so then this power is an essence, which is what we set out to show. SUB-SECTION C:--Among the proofs that guide to this claim is what I shall now show, so I say as follows. The indwelling (immanence) of form in body is at once both passive and receptive--passivity of the form and receptivity of the body. And whereas one and the same thing excludes the possibility of its being both doer and done, it becomes clear unto us that a body is not able of itself to dress itself in one mentally-grasped form and strip off another. Yet nevertheless we see a man consciously and with forethought conceiving and proceeding from one mentally-grasped form unto another, which operation is not devoid of being either an act peculiar to body, or else an act peculiar to the rational speaking power, or finally an act commonly shared between them both. It has been already shown [perhaps he here refers to the Second Section of this Essay] that it is not licit to attribute action and doing peculiarly and specially to body; nay I will say and not even to body conjointly with the rational power; since body is a co-adjutor of that power, helping towards affording an abode for any form whatsoever in that body’s own self, seeing that it has become known to us that body along with the power will both become fit subjects for this form that has thus arisen; a subject however is to be stigmatized with nothing beyond simple passivity alone, whereas both these two are [aggressive] acts and deeds. Consequently this is an act peculiar to the power. And everything that, in its act which emanates from its own self, has had no need for another thing to help it, will not need in its own structure anything beyond its own self to help it, seeing that independence or isolation in the structure of self precedes independence or isolation in the putting forth of self-emanating action. Therefore this power is an essence standing of itself [independent of body]; and consequently the rational soul is an essence. SUB-SECTION D:--Among the proofs that guide (point) to the validity of this contention is what I am now going to say.