Are methodologies theories of scientific rationality?

Historians should not use their own up-to-date methodologies to judge the rationality or correctness of the research strategies of scientists in history. For the history of science is, in part, the history of the rational growth of methodology and the historian's own up-to-date methodology is, in part, a product of the scientific revolutions of the past. Historians who use their own methodologies to judge the rationality of past research strategies are being too wise after the event. I show, using the case of Charles Darwin, how we can judge the rationality and correctness of research strategies and revolutions without being too wise after the event. I do this by rejecting the idea that methodologies double as rationality theories and by drawing instead on Popper's competing view of rationality as critical debate