The canonical version of the history of twentieth century philosophy of science tells us that Lakatos was Popper’s disciple, but it is rarely mentioned that Popper would have learned anything from Lakatos. The aim of this paper is to examine Lakatos’ influence on Popper’s philosophical system and to argue that Lakatos did have an important, yet somewhat unexpected, impact on Popper’s thinking: he influenced Popper’s evolutionary model for ‘progress’ in science. And Lakatos’ influence sheds new light on why and how (...) Popper continually revised one of the central claims of his philosophy of science: the evolutionary account of scientific theory change. (shrink)