The author analyzes pertinent aspects of Piaget's and Chomsky's points of view on language and thought, indicating the similarities in their attempts to understand the underlying structures of both functions. The major difference between Chomsky and Piaget is that the latter considers all cognitive acquisitions, including language, to be the outcome of the gradual process of construction, whereas the former seems to be assuming as innate a general ability to synthesize the successive levels reached by an increasingly complex cognitive organization. Citing examples drawn from ongoing research in Geneva, the author also challenges Chomsky's assertion that there exist highly innate specific capacities which account for the principles underlying the development of scientific knowledge.