2. Nothing is destroyed by that which makes its perfection. But the perfection of the human soul consists in a certain withdrawal from the body: for the soul is perfected by knowledge and virtue: now in knowledge there is greater perfection, the more the view is fixed on high generalisations, or immaterial things; while the perfection of virtue consists in a man's not following his bodily passions, but tempering and restraining them by reason. -- Nor is it of any avail to reply that the perfection of the soul consists in its separation from the body in point of activity, but to be separated from the body in point of being is its destruction. For the activity of a thing shows its substance and being, and follows upon its nature: thus the activity of a thing can only be perfected inasmuch as its substance is perfected. If then the soul is perfected in activity by relinquishing the body and bodily things, its substance cannot fail in being by separation from the body.
4. A natural craving cannot be in vain.* But man naturally craves after permanent continuance: as is shown by this, that while existence is desired by all, man by his understanding apprehends existence, not in the present moment only, as dumb animals do, but existence absolutely. Therefore man attains to permanence on the part of his soul, whereby he apprehends existence absolute and for all time.
6. Intelligible being is more permanent than sensible being. But the substratum of material bodies (materia prima) is indestructible, much more the potential intellect, the recipient of intelligible forms. Therefore the human soul, of which the potential intellect is a part, is indestructible.*
8. No form is destroyed except either by the action of the contrary, or by the destruction of the subject wherein it resides, or by the failure of its cause. Thus heat is destroyed by the action of cold: by the destruction of the eye the power of sight is destroyed; and the light of the atmosphere fails by the failure of the sun's presence, which was its cause. But the human soul cannot be destroyed by the action of its contrary, for it has no contrary, since by the potential intellect the soul is cognitive and receptive of all contraries. Nor again by the destruction of the subject in which it resides, for it has been shown above that the human soul is a form not dependent on the body for its being.* Nor lastly by the failure of its cause, for it can have no cause but one which is eternal, as will be shown (Chap. LXXXVII). In no way therefore can the human soul be destroyed.
9. If the human soul is destroyed by the destruction of the body, it must be weakened by the weakening of the body. But the fact is that if any faculty of the soul is weakened by the body being weakened, that is only incidentally, inasmuch as that faculty of the soul stands in need of a bodily organ, as the sight is weakened by the weakening of the organ of sight, but only incidentally, as may be shown by this consideration: if any weakness fell essentially upon the faculty, the faculty would not be restored by the restoration of the organ; but now we see that however much the faculty of sight seems weakened, it is restored, if only the organ is restored.* Since then the soul's faculty of understanding needs no bodily organ, the understanding itself is not weakened, neither essentially nor incidentally, either by old age or by any other weakness of body. But if in the working of the understanding there happens fatigue or hindrance through bodily weakness, this is not due to weakness of the understanding itself, but to weakness of other faculties that the understanding has need of, to wit, the phantasy, the memory, and the cogitative faculty.*
10. The same is evidenced by the very words of Aristotle: "Moving causes pre-exist, but formal causes are along with the things whereof they are causes: for when a man is well, then there is health. But whether anything remains afterwards, is a point to consider: in some cases there may well be something remaining: the soul is an instance, not the whole soul, but the intelligence: as for the whole soul remaining, that is perhaps an impossibility."* Clearly then, in speaking of forms, he wishes to speak of the intellect, which is the form of man, as remaining after its matter, that is, after the body. It is clear also that though Aristotle makes the soul a form, yet he does not represent it as non- subsistent and consequently perishable, as Gregory of Nyssa imputes to him:* for he excludes the intellectual soul from the general category of other forms, saying that it remains after the body and is a subsistent being (substantiam quandam).*
Hereby is banished the error of the impious in whose person it is said: We were born out of nothingness, and hereafter we shall be as though we had never been (Wisd. ii, 2); in whose person again Solomon says: One is the perishing of man and beast, and even is the lot of both: as man dies, so do beasts die: all breathe alike, and man hath no advantage over beasts (Eccles iii, 19): that he does not say this in his own person, but in the person of the ungodly, is clear from what he says at the end, as it were drawing a conclusion: Till the dust return to the earth, from whence it came; and the spirit go back to the God who gave it (Eccles xii, 7).
2.78 : That it was not the Opinion of Aristotle that the Active Intellect is a separately Subsistent Intelligence, but rather that it is a Part of the Soul
2.80, 81 : Arguments of those who wish to prove that the Human Soul perishes with the Body, with Replies to the same