The Critique of Pure Reason

Immanuel Kant's foundational work of epistemology and metaphysics, published in 1781 and substantially revised for a second edition in 1787, undertaking to determine what reason can and cannot know independently of experience. Kant argues that the mind supplies certain forms, space and time, and certain categories, including causality and substance, through which alone experience becomes possible, so that we can have secure knowledge of how things appear to us while remaining permanently unable to know things as they are in themselves. On this basis he argues that traditional metaphysical claims about the soul, the world as a whole, and God outstrip anything experience could ever confirm or deny, and that disputes over them are therefore not failures of ingenuity but a structural illusion built into reason itself when it tries to reach beyond possible experience. The book is famously difficult and was, by Kant's own account in the 1783 Prolegomena written to explain it, widely misunderstood on first publication, but it is now treated as one of the handful of works that divide the history of philosophy into before and after.