In this essay I dispute the widely held view that utility theory and decision theory are formalizations of instrumental rationality. I show that the decision theoretic framework has no deep problems accommodating the ?reasonable? qua a preference to engage in fair cooperation as such. All evaluative criteria relevant to choice can be built into a von Neumann?Morgenstern utility function. I focus on the claim that, while rational choice?driven agents are caught in the Pareto?inferior outcome, reasonable agents could ?solve? the PD (...) and cooperate. Not so, I argue. If reasonable people find themselves in PD situations they too would follow the dominant ?defect? strategy. The difference between instrumentally rational agents and those who are also reasonable is not that they would behave differently in Prisoner?s Dilemmas, but that reasonable people are more successful at avoiding the Prisoner?s Dilemma and tend to play more cooperative games. (shrink)