Chapter 6

The nouns 'substance' and 'subject' applied to the human soul

181. Our reasoning so far shows that the human soul is a single, substantial subject.
It is a subject because it is a first principle of actions endowed with feeling;(82) it is a substance because this principle is conceived by the mind as existing in itself and not in something anterior in the order of feeling and understanding.

182. We should note the difference between the noun substance and the phrase substantial subject. The word subject, which I use to express the active principle of a feeling, is employed as a name for soul in so far as it refers to the essence of the soul in all its simplicity (cf. 81). The word substance, which indicates the first act through which the whole being subsists, embraces all that the first act makes subsist; the 'substance' embraces the entire feeling both in its principle and in its term. The first feeling is, therefore, rightly called substance provided that it is seen from the point of view of principle rather than term. The act making feeling subsist is precisely the principle of the feeling.(83)

183. This distinction between substance and substantial subject shows that only a sensitive or intellective ens can be called 'substantial subject'. The word 'substance', however, is suitable for inanimate bodies in so far as our mind conceives them with their own act of subsistence.

Notes

(82) AMS, 767.

(83) In his book On the Soul, St. Gregory Thaumaturgus proves the soul is substance because it remains identical under different modifications. He starts from the following definition of substance, which is equivalent to that which I have given: 'Substance is that which, while remaining one and the same in number, receives contrary things in itself.' He then goes on to demonstrate that this is precisely what occurs with the soul. Following the same path, I began by demonstrating the identity of the soul under various, contrary modifications. I then rose to investigate the first subject of these modifications, demonstrating that it must be a first principle of all consequent activities and actions, and contain them all virtually. In this principle all the activities and actions have their root, from which they draw their subsistence (their first act of subsistence). I then concluded that by calling this first principle 'soul', the human soul has all the conditions constituting a true substance. — St. Thomas acknowledges 'acting per se' as the known characteristic of substance: 'Nothing is able to act per se except that which subsists per se', and from this principle proves that the soul is a substance (S.T., I, q. 75, art. 2). I say the same thing when I define the soul as 'a first principle of action'. However, I add 'in a given order of activity' to avoid confusing it with God (who is the universal first principle), and thus falling into pantheism.