 The use of evolutionary game theory and evolutionary techniques is a burgeoning and exciting area of contract theory. One of the many questions that arise, however, is that of why, and if so under what circumstances, we should endorse the output of evolutionary procedures. Should one equilibrium be preferred to another merely because it was the output of an evolutionary procedure? Surely we would want reasons independent of history for reflectively endorsing some equilibrium. This problem highlights the concern that social contracts that are the product of evolutionary procedures will not meet the publicity condition in the right kind of way. If the publicity condition seems harder to meet, the evolutionary approach provides a powerful and dynamic way to understand stability. Following Maynard Smith (1982), we can see stability as being an evolutionarily stable strategy equilibrium or an ESS. Basically, this is the idea that an equilibrium in an evolutionary game where successful strategies replicate at higher rates is stable if the equilibrium composition of the population in terms of strategies is not susceptible to invasion by a mutant strategy. An ESS is an application of the Nash equilibrium concept to populations. A population is evolutionarily stable when a mutant strategy is not a better response to the population than the current mix of strategies in the population. This gives a formal interpretation of Rawls’s conception of “inherent stability” and to Buchanan’s notion that social contracts should be able to withstand subversion by a sub-population of knaves. This new conception of stability combined with the dynamic nature of evolutionary games provides interesting new ways for the social contract theorist to model the output of the contract.