Cohen (1981) and others have made an interesting argument for the thesis that humans are rational: normative principles of reasoning and actual human reasoning ability cannot diverge because both are determined by the same process involving our intuitions about what constitutes good reasoning as a starting point. Perhaps the most sophisticated version of this argument sees reflective equilibrium as the process that determines both what the norms of reasoning are and what actual cognitive competence is. In this essay, I will (...) evaluate both the general argument that humans are rational and the reflective equilibrium argument for the same thesis. While I find both accounts initially appealing, I will argue that neither successfully establishes that humans are rational. (shrink)