P31: The third kind of knowledge depends on the Mind, as on a formal cause, insofar as the Mind itself is eternal.

Dem.: The Mind conceives nothing under a species of eternity except insofar as it conceives its Body’s essence under a species of eternity (by P29), i.e., (by P21 and P23), except insofar as it is eternal. So (by P30) insofar as it is eternal, it has knowledge of God/Nature, knowledge which is necessarily adequate (by IIP46). And therefore, the Mind, insofar as it is eternal, is capable of knowing all those things which can follow from this given knowledge of God/Nature (by IIP40), i.e., of knowing things by the third kind of knowledge (see the Def. of this in IIP40 S2); therefore, the Mind, insofar as it is eternal, is the adequate, or formal, cause of the third kind of knowledge (by IIID1), q.e.d.

Schol.: Therefore, the more each of us is able to achieve in this kind of knowledge, the more he is conscious of himself and of God/Nature, i.e., the more perfect and blessed he is. This will be even clearer from what follows.

But here it should be noted that although we are already certain that the Mind is eternal, insofar as it conceives things under a species of eternity, nevertheless, for an easier explanation and better understanding of the things we wish to show, we shall consider it as if it were now beginning to be, and were now beginning to understand things under a species of eternity, as we have done up to this point. We may do this without danger of error, provided we are careful to draw our conclusions only from evident premises.