1. But we have wandered far from our subject, for the purpose of our argument was to show that the mind is not restricted to any part of the body, but is equally in touch with the whole, producing its motion according to the nature of the part which is under its influence. There are cases, however, in which the mind even follows the bodily impulses, and becomes, as it were, their servant; for often the bodily nature takes the lead by introducing either the sense of that which gives pain or the desire for that which gives pleasure, so that it may be said to furnish the first beginnings, by producing in us the desire for food, or, generally, the impulse towards some pleasant thing; while the mind, receiving such an impulse, furnishes the body by its own intelligence with the proper means towards the desired object. Such a condition, indeed, does not occur in all, save in those of a somewhat slavish disposition, who bring the reason into bondage to the impulses of their nature and pay servile homage to the pleasures of sense by allowing them the alliance of their mind; but in the case of more perfect men this does not happen; for the mind takes the lead, and chooses the expedient course by reason and not by passion, while their nature follows in the tracks of its leader.
2. But since our argument discovered in our vital faculty three different varieties -- one which receives nourishment without perception, another which at once receives nourishment and is capable of perception, but is without the reasoning activity, and a third rational, perfect, and co-extensive with the whole faculty -- so that among these varieties the advantage belongs to the intellectual, -- let no one suppose on this account that in the compound nature of man there are three souls welded together, contemplated each in its own limits, so that one should think man's nature to be a sort of conglomeration of several souls. The true and perfect soul is naturally one, the intellectual and immaterial, which mingles with our material nature by the agency of the senses; but all that is of material nature, being subject to mutation and alteration, will, if it should partake of the animating power, move by way of growth: if, on the contrary, it should fall away from the vital energy, it will reduce its motion to destruction.
3. Thus, neither is there perception without material substance, nor does the act of perception take place without the intellectual faculty.