Hence so long as he can foresee two more plays of the game beyond the current play, it always serves his interest to repay the money. Once the relationship is clearly over, however, and there is no longer any chance of reprisal, there is only a short-run gain from a single final loan, and that is substantially trumped by the gain from cheating and keeping the 4,500 rubles (plus any profit he has made from them).

Russell Hardin, Trust and Trustworthiness, loc. 116