Chapter 16

The distinction between the potentiality and the essence
of the soul

903. Are the potencies of the soul distinct from its essence? We must first distinguish between the soul's general potentiality and its special potencies. I will speak about its potentiality in general and see how this differs from the essence of the soul. In the succeeding books I will discuss the various powers.
Philosophers conceive the potentiality of the soul in two ways: 1. as the soul's principle separated from its term, and 2. as the principle of the soul informed by its term.

The first way presents to our mind a non-informed principle which is neither the soul nor anything belonging to the soul. It lacks any act proper to the soul, even its act as principle, which ceases to be when separated from its term. If however we consider this potentiality in relationship with, but not isolated from its term, it ceases to be potentiality because it is a first act, that is, the soul.(63)

904. In the second way, the term is variable, as I said. This variability, which is the cause of the potentialities, pertains to the soul's term, not the principle, which is the soul itself actuated in different ways by its term. This is true potentiality that remains distinct from the soul's essence, because the essence could be conceived even if the term never varied. For example, while a sensitive soul cannot be conceived without a felt element, the felt element can vary in numerous ways and change from one way to another. Hence, in order to conceive the soul, that is, think its essence, an extended felt element is necessary whose quality need not be determined.

905. The soul, in so far as it has any kind of extended felt element, is conceived in its essence, but in so far as it has a particular felt element, is conceived in its potentiality. Thus, its potentiality differs from its essence.
The same reasoning can be applied to the object which is term of the intellective soul, except that the intellective soul has a determinate object, universal being. Here, strictly speaking, the variability does not concern the object (this is immutable) but the realities known in and through it.(64)

906. But why are the terms of the soul variable? Because they are limited. In anything limited we can conceive variation and degrees of quantity.
If however there were an ens whose term were all being and therefore the whole order of being, it would be pure act without any kind of potentiality. All being together with its whole order is perfectly one and immutable. This is proved, as mathematicians say, by the absurdity that would result from the contrary supposition. In fact, let us suppose that some variation arises in the whole. Every variation pertains to the order of being. The term of the ens, contrary to the supposition, was not therefore all being with all its order; the order lacked the variation which has now come about.
It is impossible therefore for God to have any potentiality; he is pure act. His term is all being with all its order, because it is himself. Furthermore, what we conceive in God as potency cannot be distinguished from his essence without error.

907. There is another consequence. If we conceive a potency as the essence of being, the acts we attribute to this potency must be identified with the essence of being, that is, it must be a single act whose term is all being in its perfect unity and simplicity.(65)

Nevertheless, the essence of the soul is the source of its potencies and consists in the nature of a principle actuated by its term. Clearly then, this principle, that is, the soul, when actuated differently by different terms, performs all the different kinds of acts to which the potencies are referred. This explains why St. Thomas makes the soul the remote principle of acts, and potencies the proximate principle.(66)

Notes

(63) St Thomas says: 'The potency of matter is its essence.' Here he starts from the concept of unformed matter whose act is substantial form (S.T. , I. q. 77, art. 1, ad 2). But we have seen that totally unformed matter is not an ens; properly speaking, it is the nothing conceived by the mind as the term from which springs the existence of contingent things which are drawn from nothing. It is a hypothetical abstraction.

(64) This explains what St. Thomas says when he proves the difference between essence and the powers of the soul. He poses the following objection: 'Is the sensible element essential to the sensitive soul, and the rational element to the rational soul? If so, the powers of sense and of intellect do not differ from the essence of the soul.' He replies that 'the rational and the sensible elements, in so far as different, are not received by the powers of sense and of reason but by the sensitive, rational soul' (S.T., 1, q. 77, art. 1, ad 7). This means that 'there is a sensible and a rational element which both pertain to the essence of the soul, because without them the soul cannot be conceived. Moreover, there is a sensible and a rational element which do not pertain to the essence of the soul. These vary, or vary in different degrees; they are the objects of the potentiality.'

(65) St. Thomas shows that potency cannot be identified with the essence of an ens unless the acts also are identified with its essence: 'Because potency and act divide ens and every kind of ens, both act and potency must be referred to the same kind. Thus, if the act is not in the genus of substance, the potency itself predicated of that act cannot be in the genus of substance.' From this he deduces that the potencies of the soul are not the essence of the soul because 'the action of the soul is not in the genus of substance, but in God alone is action his substance' (S.T. , 1, q. 77, art. 1).

(66) S.T. , I, q. 77, art. 1.