Immanuel Kant

The Critique of Pure Reason (1781, Riga; second edition 1787) is a book by Immanuel Kant that has exerted an enduring influence on Western philosophy. Also referred to as Kant's First Critique, it was followed by the Critique of Practical Reason (1788) and the Critique of Judgment (1790). In the preface to the first edition Kant explains that by a critique of pure reason he means not "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" and that he aims to reach a decision about "the possibility or impossibility of metaphysics in general." Kant builds on the work of empiricist philosophers such as John Locke and David Hume, as well as rationalists such as Gottfried Wilhelm Leibniz and Christian Wolff. He expounds new ideas on the nature of space and time, and tries to provide solutions to Hume's scepticism regarding human knowledge of the relation of cause and effect, and Ren Descartes' scepticism regarding knowledge of the external world. This is argued through the transcendental idealism of objects (as appearance) and their form of appearance. Kant regards the former "as mere representations and not as things in themselves," and the latter as "only sensible forms of our intuition, but not determinations given for themselves or conditions of objects as things in themselves." This grants the possibility of a priori knowledge, since objects as appearance "must conform to our cognition . . . which is to establish something about objects before they are given to us."

The Critique of Practical Reason by Immanuel Kant and translated by Thomas Kingsmill Abbott. The Critique of Practical Reason is the second of Immanuel Kant's three critiques, first published in 1788. It follows on from Kant's Critique of Pure Reason and deals with his moral philosophy. This work is called the Critique of Practical Reason, not of the pure practical reason, although its parallelism with the speculative critique would seem to require the latter term. The reason of this appears sufficiently from the treatise itself. Its business is to show that there is pure practical reason, and for this purpose it criticizes the entire practical faculty of reason. If it succeeds in this, it has no need to criticize the pure faculty itself in order to see whether reason in making such a claim does not presumptuously overstep itself (as is the case with the speculative reason). For if, as pure reason, it is actually practical, it proves its own reality and that of its concepts by fact, and all disputation against the possibility of its being real is futile.