Since the critique of psychologism initiated by Gottlob Frege and championed by Edmund Husserl, logicians and psychologists alike have adhered to a strict division of labour. This has created a gap between reasoning as a psychological phenomenon and logic. However, reasoning involves logic, and logic is the benchmark of rationality; intuitively at least, reasoning and logic are connected. Recently, attempts have been made to bridge the gap, but the strict division of labour is often eroded. Jean Piaget conceived genetic epistemology (...) as a science of the growth of knowledge, and since logical knowledge is in its purview the accusation of psychologism was omnipresent. In this paper, I outline Piaget's psychological account of the development of logic and argue that he successfully navigated the hazards of psychologism. In essence, he minds the gap by preserving the division of labour; however, by making logic the mirror of thought, he also intimated at a bridge. Concrete correspondences between logic and psychological structures of thought lie at the heart of Piaget's metaphor, and, by building on these foundations, I illustrate how an axiom schema for sentential logic can be derived from the interpropositional grouping, Piaget's psychological model of the operational structure characterising hypothetico-deductive reasoning. (shrink)