 The connection of the historicization of philosophy of science in the 1960s to the German historicist tradition is indirect, given the time-gap of decades. However, the historicists of scientific rationality discussed in this article did (or do) agree to several of the following (overlapping) tenets, most of them traceable to nineteenth-century antecedents. There exist tensions among the following claims, so internal disagreement among historicists is to be expected.