Since the expression 'that whereby we live and perceive' has two meanings, just like the expression 'that whereby we know' that may mean either knowledge or the soul, for we can speak of knowing by either, and similarly that whereby we are in health may be either health or the body or some part of the body; and since of these knowledge or health is a form, essence, or account, or if we so express it an activity of a recipient matter knowledge of what is capable of knowing, health of what is capable of being made healthy (for the activity of that which is capable of originating change seems to take place in what is changed or altered); further, since it is the soul by which primarily we live, perceive, and think: it follows that the soul must be an account and essence, not matter or a subject.