Chapter 1

Summary of the distinction between potencies and habits

935. The soul, we remember, cannot really be divided without being destroyed. Nevertheless we saw that, in order to exist, its constitution needs two entities, a principle, which is the soul itself, and a term, which is not the soul but arouses the soul's activity, a condition necessary for the soul's existence. The principle, if separated from its term, vanishes into nothing; united to its term, it is very distinct from it and, although aroused by the term as by a quasi-cause of its form, has its own activity.

936. Consequently, the activity aroused by the term which posits the principle in being, is one thing; the activity of the principle already in being is another.

937. Potencies are determined by the term and vary as the term varies; habits proceed, as from their source, from the activity proper to an already constituted principle.

938. I said that the laws which increase, diminish and modify the activity proper to the principle independently of the term, cannot be deduced a priori but must be determined by attentive observation.
Observation also shows us that the principle has a power by which it strives 1. to keep its term united to itself. 2. to maintain the term in the attitude and disposition which most satisfies the principle, or 3. to modify the term itself sufficiently to provide this attitude, and even 4. to bind the term to itself with a stronger bond. In these four different ways the principle, that is, the essence of the soul, unfolds its activity.

939. These four ways are the origin of habits through which potencies act more easily, more promptly, more effectively and more pleasantly. When the soul exercises one or more of its activities, it feels pleasure; each of the activities, as activity, is essentially sensible and pleasant. The exercise of an activity is itself an activity, and therefore pleasant. When the accidental act ceases, a trace of the experienced feeling remains in the soul which, retaining the pleasant feeling and increasing its activity, tends to reproduce it by renewing the accidental act. Habit is precisely this active tendency.
The trace of feeling experienced in the exercise of an activity endures in the soul by means of the activity proper to the soul itself. As I said, the soul does all it can to keep united and bound to itself the term which aroused the pleasant act in it. It maintains the term in an attitude suitable for reproducing the pleasant act. It also helps the term to place itself in the kind of attitude formed by the four above-mentioned ways in which the principle, that is, the essence of the soul, is active.

940. In the case of the sensitive soul, nothing of this is prevented by the cessation of the external stimulus which arouses the actual sensation. The constant term of the soul is the living body, not the external stimulus directly aroused by the sensation. True, the actual sensation ceases when the external stimulus ceases, but the disposition of the animate body does not cease. The body is maintained by the soul in that attitude and mobility through which the body can promptly and vividly re-acquire the sensation at the approach of the external stimulus.
Moreover, traces remain in the phantasy. The soul, aided by casual, internal movements that take place in a living body where everything is movement, easily re-awakens the images in the phantasy. The images pertain to the accidental acts of sensitivity and give to the rational soul a new or changed term, as sensations do.

941. Even when accidental acts have ceased, the soul itself retains those traces of its acts which constitute memory. Thus the sensible and intelligible traces remaining in the soul after accidental acts are a development of its term and increase its habitual activity.
When the rational soul has come to the point of actually having an end before it, it becomes arbiter of many sensitive and intelligible acts and uses them as means to the end. Thus it can move by itself, draw nearer to its term, bind itself more tightly to it, and apply to itself external stimuli.