The antinomies of Kant’s Critique of Pure Reason concern central metaphysical topics: if the world is finite; if it consists of simple parts; if it contains free causes; and if there belongs to the world a necessary being. Kant offers proofs for the opposed theses and antitheses of the antinomies. Though their conclusions contradict each other, Kant claims that the proofs are all valid. He further claims that they therefore must be based on a dialectical presupposition, and that transcendental idealism removes this presupposition and thus avoids contradiction. An interesting feature of Kant’s treatment is the transformation of the opposition of theses and antitheses that occur with the introduction of transcendental idealism, in his terminology a change from “analytical” to “dialectical” opposition. This distinction corresponds to that between contradictory pairs and contraries in the Aristotelian square of opposition. I will suggest that a clearer view of this transformation of status of the oppositions can be attained by considering a special version of the square, and by its extension to a hexagon.