This paper re-examines the relationship between Hegelian dialectics and the principle of reductio ad absurdum in classical logic. It argues that their relation should not be understood in terms of identity or direct reduction, but as a structural difference in the position of negation within logical and ontological systems. By introducing Fregean semantics, in which negation is formalized as a truth-value operation, and Quinean holism, which challenges the analytic/synthetic distinction and emphasizes the revisability of logical frameworks, the paper reconstructs the conceptual space in which dialectical and classical logical structures can be comparatively analyzed. The central claim is that reductio ad absurdum functions as an external mechanism for ensuring consistency within a truth-functional system, whereas Hegelian negation operates as an immanent generative principle of conceptual determination. Contradiction is therefore interpreted differently in each framework: as a sign of invalidity in classical logic, and as an internal moment of self-mediation in Hegelian logic. The paper further suggests that this distinction has contemporary relevance for non-classical logical systems, including paraconsistent and non-monotonic logics, in which contradiction is not eliminated but structurally managed. In this sense, the study contributes to a stratified understanding of negation across different levels of logical theory, bridging analytic philosophy of logic and the Hegelian dialectical tradition.
Yugo Hidaka (Wed,) studied this question.