Kant's Dialectic and the Limits of Metaphysics

The third major division of the Critique of Pure Reason, the Transcendental Dialectic, diagnoses reason's natural but illusory tendency to extend the categories, which are valid only within possible experience, beyond that domain in pursuit of unconditioned, absolute knowledge. Kant's most celebrated demonstration of this illusion is the Antinomies of Pure Reason, four pairs of arguments in which reason, applied to the world as a totality, generates equally rigorous-seeming proofs for contradictory conclusions: for instance, that the world both has and does not have a beginning in time and a limit in space, that substances both are and are not infinitely divisible, that there both is and is not freedom alongside universal natural causality, and that a necessary being both does and does not exist. For Kant, these contradictions do not reveal defects in reason's logic but the illegitimacy of treating the world as a determinate, knowable totality of things in themselves.