 We can distinguish between two ways in which game theory is relevant to ethics. The first is explanatory. Game theoretic tools can be used to explain things ranging from (i) the function of morality and (ii) general features of our moral practices, to (iii) the dynamics of morally or politically significant social issues and (iv) the emergence, existence, and stability of particular moral norms. The second way in which game theory is relevant to ethics is justificatory. Here game theoretic tools are used to justify things ranging from (i) particular norms or principles, to (ii) large scale social institutions, or (iii) general characteristics of our moral practices. In what follows, we shall consider each of these uses, including the ways in which the former complement the latter.