 Historicist philosophers did a convincing job of showing that historical evidence called the received views into question. Most philosophers today accept that verdict of history. Less successful was the attempt to formulate an adequate positive theory of rationality, both at the first-order level of scientific methodological norms (e.g., “Reject a hypothesis that makes clearly false predictions” or “Use double-blind experimental methods when dealing with cognitive agents”) and at the metamethodological level, where they faced the problem of how to rationally select among competing theories of scientific rationality, without circularity. The disagreements here raised the question of whether there is a general theory of scientific rationality to be found, or a need for one.