Now, the faculties which guide us in action and in the apprehension of truth are three: sense, reason, 141 and desire.

The first of these cannot originate action, as we see from the fact that brutes have sense but are incapable of action.

If we take the other two we find two modes of reasoning, viz. affirmation and negation [or assent and denial], and two corresponding modes of desire, viz. pursuit and avoidance [or attraction and repulsion].

Now, moral virtue is a habit or formed faculty of choice or purpose, and purpose is desire following upon deliberation.