Abstract This paper focuses on the linguistic evidence base provided by proponents of conceptualism (e.g., Chomsky) and rational realism (e.g., Katz) and challenges some of the arguments alleging that the evidence allowed by conceptualists is superior to that of rational realists. Three points support this challenge. First, neither concep-tualists nor realists are in a position to offer direct evi-dence. This challenges the conceptualists ’ claim that their evidence is inherently superior. Differences between the kinds of available indirect evidence will be discussed. Second, at least some of the empirical evidence provided by the conceptualist is flawed. It is not obtained indepen-dently of theoretical commitments, alternative interpreta-t...