tit-for-tat is an optimal (and Nash Equillibrium) strategy for recurring prioner's dilemma if you don't how many games you will play. If you know the number of

tit-for-tat is an optimal (and Nash Equillibrium) strategy for recurring prioner's dilemma if you don't how many games you will play. If you know the number of games, or it is the last game, always-defect is the Nash Equillibrium. Depending on social circumstances (such as in a Gulag), murder can be the Nash equillibrium strategy if you optimize for survival. It's just that such circumstances are outside of the experience of most people, and most people today cannot even imagine it.