Naturalia non sunt in nobis, the natural being marked off from the voluntary (note [3.106a]). The natural appetites, apart from their voluntary gratification to this or that effect, do not induce acts of the individual man, but acts of the species man. Such acts are not the acts of Charles or James: they are racial, not personal; and so long as they remain racial, and are not in any way brought about or taken up by the will of the person in whom they occur, they are outside of the category of morality, being neither moral nor immoral, but organic.

Of God and His Creatures: 3.113