Although this book seeks to show that the naturalists are wrong to criticize the normativity in moral theory, nonetheless in Part I, I shall be taking the naturalists' side, identifying what it is about the moral objectivists' norms that cannot, in the naturalists' view, pass “scientific muster.” This involves explaining what “scientific muster” is supposed to be and why a theory is commonly thought to be disreputable unless it passes it.

Surprisingly, however, this is a difficult project. In this chapter, I will review a variety of ways that naturalists have tried to show the unscientific nature of objective moral norms, none of which I shall argue is successful. It is remarkable that objectivist moral theorists have been so much on the defensive in recent years, given that the naturalists' arguments against their theories have been incomplete, or imprecise, or have, in various ways, begged the question at issue.

I will then spend the next two chapters developing a more successful argument on behalf of the naturalists. Once we are clear about the unnatural component within objectivist moral theories, we will be in a position to look for it in the theories of the naturalists in Part II.