Plotinos: Complete Works, v. 2 In Chronological Order,...

This difference between souls is caused principally by the constitution of the bodies they animate; also by the moral habits, the activities, the thoughts and behavior of these souls in earlier existence. According to Plato109 the choice of the souls' condition depends on their anterior existence. On observing the nature of souls in general, we find that Plato recognizes differences between them by saying that some souls occupy the second or third ranks.110 Now we have said that all souls are (potentially) all things,111 that each is characterized by the faculty principally exercised thereby, that is, that some souls unite with the intelligible world by actualization, while others do so in thought or desire.112 Souls, thus contemplating different objects, are and become all that they contemplate. Fulness and perfection also belong to soul, but in this respect they are not all identical, because variety is the law that directs their co-ordination. Indeed, the universal113 reason is on the one hand manifold, and on the other varied, like a being that is animate, and which possesses manifold forms.114 In this case, there is co-ordination; beings are not entirely separated from each other, and there is no place for chance either in real beings, nor in bodies; consequently the number of beings is definite. To be individual, beings must first be stable, then they must remain identical, and last, they must numerically be one in order to achieve individuality.

Bodies which by nature perpetually ooze away, because for them form is something incidental, never possess formal existence but by their participation in (and imitation of), genuine "Beings." On the contrary, for the latter, that are not composite, existence consists in each of them being numerically single, in possessing this unity which dates from the beginning, which does not become what it was not, and which will never cease being what it is. If indeed they cannot exist without some producing principle, that principle will not derive them from matter. It will have to add to them something from its own being. But if intelligible entities thus have at times more, and at times less, perfection, they will change; which would contradict their (nature, or) "being," which is to remain identical. Why indeed should they become such as they are now, and why should they not always have been such as they now are? Further, if they be at times more or less perfect, if they "become," they are not eternal. But it is granted that the Soul (as an intelligible being) is eternal.