The Critique of Pure Reason is one of the most influential works in the history of philosophy and marks a turning point and the beginning of modern philosophy. Also referred to as Kant's "first critique," it was followed by the Critique of Practical Reason and by the Critique of Judgment. In the preface to the first edition, Kant explains what he means by a critique of pure reason: "I do not mean by this a critique of books and systems, but of the faculty of reason in general, in respect of all knowledge after which it may strive independently of all experience."

Immanuel Kant (1724-1804) was a German philosopher, who, according to the Stanford Encyclopedia of Philosophy is "the central figure of modern philosophy." Kant argued that fundamental concepts of the human mind structure human experience, that reason is the source of morality, that aesthetics arises from a faculty of disinterested judgment, that space and time are forms of our understanding, and that the world as it is "in-itself" is unknowable. Kant took himself to have effected a Copernican revolution in philosophy, akin to Copernicus' reversal of the age-old belief that the sun revolved around the earth.