 In “The History of Science and its Rational Reconstructions” (HS&amp;IRR) Lakatos develops a theory of how to do the history of science, which, with some adjustments, can be blown up into an account of how to do intellectual history in general. For Lakatos, the default assumption in the history of science is that the scientists in question are engaged in a more-or-less rational effort to solve a set of (relatively) “pure” problems (such as “How to explain the apparent motions of the heavenly bodies consistently with a plausible mechanics?”). A “rational reconstruction” in the history of science, employs a theory of (scientific) rationality in conjunction with an account of the problems as they appeared to the scientists in question to display some intellectual episode as a series of rational responses to the problem-situation. On the whole, it is a plus for a theory of [scientific] rationality if it can display the history of science as a relatively rational affair and a strike against it if it cannot. Thus in Lakatos’s opinion, naïve versions of Popper’s falsificationism are in a sense falsified by the history of science, since they represent too much of it as an irrational affair with too many scientists hanging on to hypotheses that they ought to have recognized as refuted. If the rational reconstruction succeeds—that is if we can display some intellectual development as a rational response to the problem situation—then we have an “internal” history of the developments in question. If not, then the “rational reconstruction of history needs to be supplemented by an empirical (socio-psychological) ‘external history’” (HS&amp;IRR: 102). Non-rational or “external” factors sometimes interfere with the rational development of science. “No rationality theory will ever solve problems like why Mendelian genetics disappeared in Soviet Russia in the 1950s” [the reason being that Lysenko, a Stalin favourite, acquired hegemonic status within the world of Soviet biology and persecuted the Mendelians] (HS&amp;IRR: 114).