Many contemporary logicians acknowledge a plurality of logical theories and accept that theory choice is in part motivated by logical evidence. However, just as there is no agreement on logical theories, there is also no consensus on what constitutes logical evidence. In this paper, I outline Jean Piaget’s psychological theory of reasoning and show how he used it to diagnose and solve one of the paradoxes of material implication. I assess Piaget’s use of psychology as a source of evidence for (...) logical theory in light of reservations raised by psychologism, and I highlight some ramifications for exceptionalism and anti-exceptionalism about logic by considering his use of psychology as logical evidence in the framework of genetic epistemology, Piaget’s research programme. I conclude that Piaget’s psychological theory of reasoning not only plausibly serves as a source of evidence for logical theory but also makes a strong case for anti-exceptionalism about logic. (shrink)

The Strong Normative Constitutivity reading of logical laws in Frege argues that although he regards logical laws as purely descriptive, he in fact accepts that they are normatively constitutive of the act of judgement. There are passages in which Frege seems to commit himself to such an idea. However, we can understand what Frege argues in those passages based only on his conception of logical laws as the most general descriptive laws and his objectivism about truth. If my suggested interpretation (...) is correct, there is a reason to think that logical laws are merely descriptive for Frege. Further, my interpretation shows that the central issue between Frege and psychological logicians is the nature of truth. (shrink)

The neo-Kantian transcendentalist reading of the epistemic status of logical axioms in Frege argues that he is committed to the neo-Kantian idea that we are epistemically justified in accepting logical axioms because accepting them is necessary for achieving epistemically crucial goals. However, I show that Frege hesitates to be fully committed to neo-Kantian transcendentalism because he struggles to accept the idea that such a teleological reason can constitute an epistemic warrant. This interpretation shows some crucial aspects of his philosophy of (...) logic, such as his understanding of the relationship between the simplicity and the sufficiency of logical systems. (shrink)

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)