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 conceptualists nor realists are in a position to offer direct evidence. 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 independently of theoretical commitments, alternative interpretations have not been ruled out, and some of the thought experiments intended to extend the evidence base are conceptually flawed. Third, the widely held assumption that rational realism disallows empirical evidence relevant to linguistics is dubious. It will be shown that the limitation imposed by rational realism concerns strictly formal linguistics. The rationalist realist has no reason to impose any restriction on the evidence relevant to psycholinguistics. I conclude that it is a mistake to dismiss realism based on the assumption that it imposes undue restrictions on evidence that is relevant to linguistics. (shrink)