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Talk:Critique of Pure Reason

The Critique of Pure Reason (Kritik der reinen Vernunft, KrV) by Immanuel Kant, (first published in 1781, second edition 1787), is one of the most influential works in the history of philosophy, and comes at the end of the period known as the Enlightenment. It deals with questions concerning the foundations and extent of human knowledge and builds on the work of empiricist philosophers such as John Locke and David Hume, as well as taking into account the theories of rationalist philosophers such as Leibniz and Wolff.

Sometimes referred to as Kant's First Critique, it was followed in 1788 by the Critique of Practical Reason and in 1790 by the Critique of Judgment. Kant also wrote a more popular version of the First Critique entitled, Prolegomena to any Future Metaphysics that Will Be Able to Come Forward as Science (1783), in which he strove to make his ideas more accessible to the general reader.

The book contains radically new ideas on the nature of space and time, and also claims to solve the problem which Hume posed regarding our knowledge of the relation of cause and effect. These are central themes of the book, and Kant also claims to have assessed the ability of the human mind to engage in metaphysics.

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." Such knowledge is referred to by Kant as "a priori" knowledge, by comparison with knowledge obtained through experience, which is termed "a posteriori". The hallmark of "a priori" knowledge is, according to Kant, that it expresses a necessary truth. Statements which are necessarily true are such as cannot be negated without becoming false - they are universally true and do not allow of any exceptions. Examples provided by Kant include the propositions of mathematics; propositions "from the understanding in its quite ordinary employment", such as "Every alteration must have a cause"; as well as propositions from "natural science (physics)", such as "in all changes in the material world the quantity of matter remains unchanged".

Kant believed that he had discovered another attribute of propositions, which allowed him to frame the problem of a priori knowledge in a new way. This was the distinction between "analytic" and "synthetic" judgments. To say that a sentence is "analytic" is, according to Kant, to say that what is stated in the predicate-concept of the sentence is already contained (albeit covertly) in the subject-concept of that sentence. The example he provides is the sentence, "All bodies are extended". This sentence is, according to Kant, "analytic", since the predicate-concept ("extended") is already contained in - or "thought in" - the subject-concept of the sentence ("bodies"). On the other hand, the judgment, "All bodies are heavy" was thought by Kant to be synthetic, since "I do not include in the concept of body in general the predicate 'weight'". Synthetic judgments therefore add something to a concept, whereas analytic judgments only explain what is already contained in the concept.

The distinctive character of "analytic" judgments was, therefore, for Kant, that they can be known to be true simply by an analysis of the concepts contained in them - or, alternatively, are true by definition. Prior to Kant, it was thought that all necessary truth had the character of being "analytic". Kant, however, argued that not all necessary truths are analytic, but that some of them are synthetic. Having explained that the basis of analytic judgments lies in the principle of contradiction, (or the principle of identity), the task he set out to achieve in the Critique of Pure Reason was to explain the grounds of those judgments which are necessary and synthetic - and these he termed "a priori synthetic judgments". Thus, we arrive at the formulation of the fundamental question of the Critique of Pure Reason: "Now the proper problem of pure reason is contained in the question: How are a priori synthetic judgments possible?"