Chapter XV.—The Lust and Desire of Sentient Things; Demons; Animals Sentient; So Also the Sun and the Moon and Stars; The Platonic Doctrine, Not the Christian. Whence, then, come pleasure and desire? For these are the principal evils that they talk of and hate. Nor does matter appear to be anything else. That these things, indeed, only belong to animals which are endowed with sense, and that nothing else but that which has sense perceives desire and pleasure, is manifest. For what perception of pleasure and pain is there in a plant? What in the earth, water, or air? And the demons, if indeed they are living beings endowed with sense, for this reason, perhaps, are delighted with what has been instituted in regard to sacrifices, and take it ill when these are wanting to them; but nothing of this sort can be imagined with respect to God. Therefore those who say, “Why are animals affected by pleasure and pain?” should first make the complaint, “Why are these animals endowed with sense, or why do they stand in need of food?” For if animals were immortal, they would have been set free from corruption and increase; such as the sun and moon and stars, although they are endowed with sense. They are, however, beyond the power of these, and of such a complaint. But man, being able to perceive and to judge, and being potentially wise,—for he has the power to become so,—when he has received what is peculiar to himself, treads it under foot.