Abstract

A number of moral philosophers have endorsed instances of the following curious argument: it would be better if a certain moral theory were true; therefore, we have reason to believe that the theory is true. In other words, the mere truth of the theory—quite apart from the results of our believing it or acting in accord with it—would make for a better world than the truth of its rivals, and this fact provides evidence of the theory’s truth. This form of argument may seem to be an obvious non-starter. After all, the fact that the truth of some empirical claim, say, the claim that there is an afterlife, would be desirable does not, by itself, give us any reason to believe it. But I argue that, when it is properly understood, this form of argument—which I call the better world argument—is valid in moral philosophy. I develop and defend a version of the argument that rests on the view that the correct moral theory cannot exhibit a certain form of self-defeat—a form that, as far as I know, has not been discussed in the literature. I also identify two promising applications of this form of argument. The first is a defense of permissions to promote one’s own private aims, rather than promote the greater good, and the second, an argument against the possibility of moral dilemmas