One of the forms of moral realism is the ontological realism which is divided into moral naturalism and moral non-naturalism. Moral naturalism is also divisible into three general kinds: reductive moral naturalism, non-reductive moral naturalism, and new-Aristotelian moral naturalism that is discussed by some people such as Philippa Foot. In Foot's view, moral goodness in human beings is like the natural goodness in plants and animals. So, since the natural goodness in plants and animals as a factual thing is the necessary condition of their flourishing, the moral goodness (moral virtue) in human beings as a factual and objective thing is also a necessary requirement of human flourishing. Therefore, evaluation in plants and animals, 011 the one hand, and in human beings, on the other hand, has logically the same structure. Responding to the problem to the effect that moral goodness in human beings unlike animals is determined by reason and rationality, Foot introduces a new conception of practical reason upon which not only practical rationality does not determine moral goodness, but reversely the moral goodness is the necessary condition of practical rationality in human beings.