Reply. Whatever things are necessarily in conjunction and proportion with one another, are made many or one together, each by its own cause. If the being of the one depends on the other, its unity or multiplication also will depend on the same: otherwise it will depend on some extrinsic cause. Form then and matter must always be in proportion with one another, and conjoined by a certain natural tie. Hence matter and form must vary together in point of multiplicity and unity. If then the form depends on the matter for its being, the multiplication of the form will depend on the matter, and so will its unity. But if the form is in no such dependence on the matter, then, -- though it will still be necessary for the form to be multiplied with the multiplication of the matter, -- the unity or multiplicity of the form will not depend on the matter. But it has been shown (Chap. LXVIII, and note [Chapter 79], that the human soul is a form not dependent on matter for its being. Hence it follows that, though souls are multiplied as the bodies which they inform are multiplied, still the fact of bodies being many cannot be the cause of souls being many.* And therefore there is no need for the plurality of souls to cease with the destruction of their bodies.
Arg. 2. The formal nature (ratio formalis [Chapter 48 note i ; Chapter 56 note i]) of things is the cause of their differing in species. But if souls remain many after the perishing of their bodies, they must differ in species, since in souls so remaining the only diversity possible is one of formal nature. But souls do not change their species by the destruction of the body, otherwise they would be destroyed too, for all that changes from species to species is destroyed in the transition. Then they must have been different in species even before they parted from their bodies. But compounds take their species according to their form. So then individual men must differ in species, an awkward conclusion consequent upon the position that souls remain a multitude after their bodies are gone.
Reply. It is not any and every diversity of form that makes a difference of species. The fact of souls separated from their bodies making a multitude follows from their forms being different in substance, inasmuch as the substance of this soul is different from the substance of that. But this diversity does not arise from the souls differing in their several essential constitutions, but from their being differently commensurate with different bodies: for one soul is commensurate with one body and not with another.* These commensurations remain in souls even when their bodies perish, as the substances of the souls also remain, not being dependent on their bodies for their being. For it is by their substances that souls are forms of bodies: otherwise they would be united with their bodies only accidentally, and soul and body would not make up an essential but only an accidental unity. But inasmuch as they are forms, they must be commensurate with their bodies. Hence it is clear that their several different commensuratenesses remain in the departed souls, and consequently plurality.
Arg. 3. It seems quite impossible, on the theory of those who suppose the eternity of the world, for human souls to remain in their multitude after the death of the body. For if the world is from eternity, infinite men have died before our time. If then the souls of the dead remain after death in their multitude, we must say that there is now an actual infinity of souls of men previously dead. But actual infinity is impossible in nature.*
Reply. Of supporters of the eternity of the world, some have simply allowed the impossibility, saying that human souls perish altogether with their bodies. Others have said that of all souls there remains one spiritual existence which is common to all, -- the active intellect according to some,* or with the active also the potential intellect according to others.* Others have supposed souls to remain in their multitude after their bodies; but, not to be obliged to suppose an infinity of souls, they have said that the same souls are united to different bodies after a fixed period;* and this was the opinion of the Platonists, of which hereafter (Chap. LXXXIII). Others, avoiding all the aforesaid answers, have maintained that there was no difficulty in the existence of an actual infinity of departed souls: for an actual infinity of things, not related to one another, was only an accidental infinity, in which they saw no difficulty; and this is the position of Avicenna and Algazel.* Which of these was the opinion of Aristotle is not expressly set down in his writings, although he does expressly hold the eternity of the world. But the last mentioned opinion is not inconsistent with his principles: for in the Physics, III, v, his argument against an actual infinity is confined to natural bodies, and is not extended to immaterial substances. Clearly however the professors of the Catholic faith can feel no difficulty on this point, as they do not allow the eternity of the world.*
Arg. 5. It is impossible for any substance to exist destitute of all activity. But all activity of the soul ends with the body, as may be shown by simple enumeration. For the faculties of the vegetative soul work through bodily qualities and a bodily instrument; and the term of their activity is the body itself, which is perfected by the soul, is thereby nourished and developed, and comes to furnish the generative products. Also all the activities of the faculties of the sensitive soul are accomplished through bodily organs; and some of them are accompanied by (sensible) bodily change, as in the case of the passions. As for the act of understanding, although it is not an activity exercised through any bodily organ, nevertheless its objects are phantasms, which stand to it as colours to sight: hence as sight cannot see without colours, so the intellectual soul cannot understand without phantasms. The soul also needs, for purposes of understanding, the faculties which prepare the phantasms to become actual terms of intellect, namely, the cogitative faculty and the memory, of which it is certain that they cannot endure without the body, seeing that they work through organs of the body. Hence Aristotle says that "the soul by no means understands without a phantasm," and that "nothing understands without the passive intellect," by which name he designates the cogitative faculty, "which is perishable"; and that "we remember nothing" after death of the things that we knew in life.* Thus then it is clear that no activity of the soul can continue after death, and therefore neither can its substance continue.
Reply. The assertion that no activity can remain in the soul after its separation from the body, we say, is incorrect: for those activities remain which are not exercised through organs, and such are understanding and will. As for activities exercised through bodily organs, as are the activities of the vegetative and sentient soul, they do not remain. But we must observe that the soul separated from the body does not understand in the same way as when united with the body: for everything acts according as it is. Now though the being of the human soul, while united with the body, is perfect (absolutum), not depending on the body, still the body is a sort of housing (stramentum*) to it and subject receptive of it. Hence the proper activity of the soul, which is understanding, while independent of the body in this that it is not exercised through any bodily organ, nevertheless finds in the body its object, which is the phantasm.* Hence, so long as the soul is in the body, it cannot understand without a phantasm,* nor remember except by the cogitative and reminiscent faculty whereby phantasms are shaped and made available (Chap. LXXIII); and therefore this method of understanding and remembering has to be laid aside when the body is laid aside. But the being of the departed soul belongs to it alone without the body:* hence its intellectual activity will not be accomplished by regard to such objects as phantasms existing in bodily organs, but it will understand by itself after the manner of those intelligences that subsist totally apart from bodies (Chapp. XCI-CI), from which superior beings it will be able to receive more abundant influence in order to more perfect understanding.
We may see some indication of this even in living men. When the soul is hampered by preoccupations about its body, it is less disposed to understand higher things. Hence the virtue of temperance, withdrawing the soul from bodily delights, helps especially to make men apt to understand.* In sleep again, when men are not using their bodily senses, they have some perception of things to come, impressed upon them by superior beings, and attain to facts that transcend the measure of human reasonings.* This is much more the case in states of syncope and ecstasy, as the withdrawal from the bodily senses is there greater. And that is what one might expect, because, as has been pointed out above (Chap. LXVIII), the human soul being on the boundary line between corporeal and incorporeal substances, and dwelling as it were on the horizon of eternity and time, it approaches the highest by receding from the lowest. Therefore, when it shall be totally severed from the body, it will be perfectly assimilated to the intelligences that subsist apart, and will receive their influence in more copious streams. Thus then, though the mode of our understanding according to the conditions of the present life is wrecked with the wreck of the body, it will be replaced by another and higher mode of understanding.
But memory, being an act exercised through a bodily organ, as Aristotle shows,* cannot remain in the soul after the body is gone; unless memory be taken in another sense for the intellectual hold upon things known before: this intellectual memory of things known in life must remain in the departed soul, since the intellectual impressions are indelibly received in the potential intellect (Chap. LXXIV). As regards other activities of the soul, such as love, joy, and the like, we must beware of a double meaning of the terms: sometimes they mean passions, or emotions, which are activities of the sensitive appetite, concupiscible or irascible,* and as such they cannot remain in the soul after death, as Aristotle shows:* sometimes they mean a simple act of will without passion, as Aristotle says that "The joy of God is one, everlasting, and absolute," and that "In the contemplation of wisdom there is admirable delight"; and again he distinguishes the love of friendship from the love of passion.* But as the will is a power that uses no bodily organ, as neither does the understanding, it is evident that such acts, inasmuch as they are acts of will, may remain in the departed soul.
2.79 : That the Human Soul does not perish with the Body
2.82 : That the Souls of Dumb Animals are not Immortal