How do antinomies challenge metaphysical claims in Kant’s Critique of Pure Reason?

In his Critique of Pure Reason, Immanuel Kant used the concept of antinomies to demonstrate the inherent limitations of human reason when it attempts to make claims about the unconditioned or supersensible world.12

An antinomy arises when pure reason generates two contradictory propositions—a thesis and an antithesis—that both appear equally justified by logical proof. For example, Kant identified contradictions regarding whether the universe has a beginning, whether it consists of simple parts, whether freedom exists, and whether a necessary being exists.12

These contradictions challenge metaphysical claims by revealing that reason oversteps its bounds when it tries to apply concepts beyond the realm of possible experience. Kant resolved these antinomies by distinguishing between phenomena (things as they appear to us) and noumena (things-in-themselves). He argued that because human knowledge is limited to the phenomenal world—structured by our own minds—we can never achieve scientific knowledge of the noumenal realm. Consequently, while metaphysics cannot provide knowledge of the supersensible, these antinomies compel reason to self-examine, ultimately clearing the way for moral belief.213