 With all that said, the threat of relativism remains, for how can a good, non-whiggish historicist have a trans-historical measure of progress? Laudan’s answer was that we can whiggishly measure scientific progress by our own standards, regardless of what the goals of the historical investigators were. This sounds right about what we do. But if the reasons why the historical scientists in the trenches made the decisions they did do not really matter to us (or to any given generation), retrospectively, then how is rationality providing a methodological guide or causal explanation why historical scientists made the decisions they did?  Their individual rationality would seem to become irrelevant. And why, then, is rationality the central problem of philosophy of science?