Abstract

The ethical naturalist asks us to take seriously the idea that practical norms are a species of natural norms, such that moral goodness is a kind of natural goodness. The ethical naturalist has not demonstrated, however, how it is possible for a power of reason to be governed by natural norms, because her own attempts to do this have led her into a dilemma. If she takes the first horn and stresses that ethical naturalism provides objective, natural norms of the species, then she fails to show how such norms are practical, or operative from a deliberative point of view. If she takes the second horn and stresses that ethical naturalism yields a picture of knowledge of human life that is practical because it comes through virtuous dispositions of intellect and will, then she fails to have an account of how it is knowledge of facts about a life form, potentially accessible to a non-human knower. In this paper, I argue that one potential resolution to this dilemma can be found in the writings of Thomas Aquinas. On a broadly Thomist account of practical reason, the first principles of practical reason are our common human ends or goods, which are constitutive of a good human life. The work of practical reason on this naturalistic account is twofold: to conceive and order these ends into some general conception of how to live, and to apply this general conception to the particular situations of one’s life in order to realize one’s vision of the good life, here and now.