 This extensive form game depicts Laura’s true payoffs, including the cost of guilt that Sidgwick would call an internal sanction. In this game if Claudia performs as promised, then to follow P as justice requires is now Laura’s best response. However, this isn’t because we’ve simply assumed that one couldn’t ever stand to gain by breaking a promise. To see why, note that if Claudia breaks her promise first, then A continues to be Laura’s best response. As we saw in our discussion of the evolution of cooperation, morality can’t require us to be suckers. Or, to use Kavka’s helpful terminology, justice may forbid violating a covenant offensively by breaking one’s promise unexpectedly, while permitting defensive violations of covenants that others can no longer reasonably expect us to honor (Kavka 1986: 139). Accordingly, if Claudia offensively violates her covenant with Laura by following A, then if Laura responds in kind, Laura’s violation should not give rise to the internal sanctions associated with having committed an injustice. Furthermore, note that the presence of internal sanctions can change things even when these aren’t universally felt. For instance, even if Claudia herself would feel negligible guilt for offensively violating their covenant, if Claudia knows that Laura would suffer the internal sanction cost \(\gamma &gt; 1\) of offensive violation, then Claudia can expect Laura to perform when she does as well, and in this case she fares best by following P at the outset.