What about strangers? Darwinian theory says we should be indifferent to them because they are genetically alien to us. Even so, we do trade with strangers and coexist with them and generally treat them decently and fairly. The Darwinians explain this as a consequence of “reciprocal altruism,” which is the moral equivalent of “I’ll be nice to you, so that you will be nice to me.” This strategy can take various forms—”first be nice to me, and then I’ll be nice to you” or “I’ll continue to be nice to you as long as you are nice to me”—but the general idea is that morality is a strategy we employ for our own long-term benefit. Darwinians go to elaborate lengths to establish these strategies, resorting to game theory and obscure analogies from the behavior of ants and vampire bats, but I don’t need to reproduce those arguments; the underlying logic is clear and persuasive enough.