We begin, in section 2, with a brief sketch of a cluster of assumptions about human desires, beliefs, actions, and motivation that are widely shared by historical and contemporary authors on both sides in the debate. With this as background, we’ll be able to offer a more sharply focused account of the debate. In section 3, our focus will be on links between evolutionary theory and the egoism/altruism debate. There is a substantial literature employing evolutionary theory on each side of the issue. However, it is our contention that neither camp has offered a convincing case. We are much more sanguine about recent research on altruism in social psychology, which will be our topic in section 4. Though we don’t think this work has resolved the debate, we will argue that it has made illuminating progress – progress that philosophers interested in the question cannot afford to ignore.