 The winds driving the sort of disciplinary cross-pollination we describe do not blow in one direction. As philosophers writing for an encyclopedia of philosophy, we are naturally concerned with the ways empirical research might shape, or re-shape, philosophical ethics. But philosophical reflection may likewise influence empirical research, since such research is often driven by philosophical suppositions that may be more or less philosophically sound. The best interdisciplinary conversations, then, should benefit both parties. To illustrate the dialectical process we have described, we will consider a variety of topics in moral psychology. Our primary concerns will be philosophical: What are some of the most central problems in philosophical moral psychology, and how might they be resolved? However, as the hybrid nature of our topic invites us to do, we will pursue these questions in an interdisciplinary spirit, and are hopeful that our remarks will also engage interested scientists. Hopefully, the result will be a broad sense of the problems and methods that will structure research on moral psychology during the 21st century.