Piaget's studies clearly highlight two qualitative advances made during the preoperational period. The first is the breakthrough of representational intelligence, beginning around 2 years of age. The second is the emergence of coordinated representational thought, beginning around 4 years of age. This paper focuses on the second advance, which Piaget calls the "intuitive substage." The paper begins with a summary of intuitive thought as conceived in the classical Genevan studies of the 1940s and 1950s, then moves to the more detailed analyses provided in three relatively recent sources: (1) the research on the psychology of functions; (2) studies of possibility and necessity; and (3) research on the logic of meaning. These analyses elaborate on the logical structure of intuitive thought and describe the emergence of logical modalities and the abstraction of representational meanings during the intuitive period. It is concluded that these Genevan accounts of the transition at 4 years of age are consistent with current research and theory in such areas as children's theories of mind, and children's understanding of certainty and probability, and of appearance and reality. (RH)