Immanuel Kant begins by questioning whether metaphysics can legitimately be considered a science, noting that while other disciplines advance continuously, metaphysics remains trapped in endless disputes. Prompted by David Hume's critique of causality, Kant asks how synthetic judgments a priori are possible, arguing that such propositions form the foundation of both pure mathematics and natural science. He demonstrates that space and time are not properties of things in themselves, but rather the subjective forms of human sensuous intuition. This crucial insight forms the basis of his critical idealism, proving that human knowledge is strictly limited to the realm of possible experience.
Building on this foundation, Kant explores how the pure concepts of the understanding, or categories, actively prescribe laws to nature rather than merely deriving them from experience. He explains that while our understanding makes empirical knowledge possible by organizing perceptions, reason inevitably overreaches these boundaries when it seeks absolute completeness. This overreaching leads to unavoidable dialectical illusions, manifest as cosmological antinomies where reason seemingly contradicts itself. Kant resolves these antinomies by distinguishing between appearances and things in themselves, thereby rescuing practical freedom while preserving the necessity of natural law.
In the final sections, Kant addresses the theological idea of a Supreme Being, arguing that speculative reason cannot prove its objective reality through dogmatic proofs. Instead, he suggests a regulative and symbolical use of such concepts, which serve to guide our understanding toward maximum systematic unity and support moral principles. He concludes that a thorough critique of pure reason is the only reliable method to reform metaphysics, shifting it from a pseudo-science of endless debate into a definitive system of philosophy.
