 Moral philosophers tend to focus on questions about the justification of moral claims, the existence and grounds of moral truths, and what morality requires of us. These are very different from the empirical questions pursued in the sciences, but how we answer each set of questions may have implications for how we should answer the other. As we will see, though the two sets of issues are distinct, the scientific explanatory projects raise potential challenges for certain philosophical views, and at the same time attention to philosophical issues raises doubts about some of the explanatory claims made in the name of science, which often rely on controversial philosophical assumptions. Progress in this area will not be made either by doing moral philosophy in isolation from the sciences or by taking morality out of the hands of philosophers and looking to scientific inquiry in isolation. More promising would be a careful examination of the ways in which the scientific and philosophical projects inform each other.