To judge by a very quick scan of the literature of economics over the past two centuries, the occurrence of the word "rational" and its cognates was both infrequent and sporadic before the 1940s. Of course, a quick scan of the literature is an imperfect substitute for more careful and intensive research by historians of economic thought, and a thorough search through that literature (especially through those portions written in languages other than English) might lead to a very different impression than the one given here.¹