This article discusses how the results of infant research challenge the assumptions of the classical sciences of social behaviour. According to A.J. Bergesen, the findings of infant research invalidate Durkheim's theory of mental categories, thus requiring a re-theorizing of sociology. This article argues that Bergesen's reading of Emile Durkheim is incorrect, and his review of the infant research in fact invalidates his argument. Reviewing the assumptions of sociology in the light of the findings of infant research, it is argued that the real challenge is to formulate a research strategy that combines the findings of the two sciences.