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Last Reviewed on June 19, 2019, by eNotes Editorial. Word Count: 429

Critique of Pure Reason by German philosopher Immanuel Kant (22 April 1724 – 12 February 1804) was originally published in 1781. It is widely acknowledged to be among the most important philosophical works of the modern period, transforming the way philosophers regard fundamental questions about the nature of being and knowledge.

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In this work, Kant takes a systematic and scientific approach to questions of metaphysics (in its classical sense of the study of "being qua being") and epistemology. One especially important aspect of his approach to the topic is his emphasis on the limits of human knowledge. He tries to precisely demarcate what can be known with certainty from things of which it is only possible to have limited knowledge and those about which no real knowledge is possible.

One key distinction Kant makes is between things known a priori (i.e., prior to experience) and those known a posteriori (i.e., knowable only after having experience of those things). The truths of mathematics, for example, are known a priori. One knows that if one places two apples in a basket and then adds two additional apples, one will have four apples. One has this knowledge without the need to actually place apples in baskets or even to have ever encountered an apple. On the other hand, the color of a neighbor's cat is known a posteriori; it can only be determined after one has had the experience of seeing the cat itself or a picture of it. Certain truths of logic and mathematics are examples of a priori knowledge, while facts about the external world, such as the population of a country or the distance between two cities, are known a posteriori by empirical measurement.

Another important distinction is between things known analytically and things known synthetically. Analytic knowledge inheres in the thing being analyzed. For example, one can determine the truth of the statement "a bachelor is an unmarried man" or "all dogs are quadrupeds" simply by knowing the definition of the relevant terms. The statement that "dogs are often beloved pets" requires knowledge that does not inhere in the definition of a dog.

A particularly important class of knowledge for Kant is synthetic a priori intuitions, which include the notions that effects have causes and that all things are extended in space and time. These intuitions, for Kant, condition our experiences. Rather than experience things-in-themselves (noumena) directly, people's experience is of phenomena, which are filtered through human consciousness conditioned by synthetic a priori intuitions. This insight harmonizes the empiricism of Hume and other empiricists with the rationalism of Leibniz, Berkeley, and Descartes.


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Last Updated on May 6, 2015, by eNotes Editorial. Word Count: 165

Immanuel Kant’s Critique of Pure Reason is an established classic in the history of epistemology. First published in 1781 and then revised in 1787, it is the fruit of Kant’s later years and, as such, clearly reflects the insight and wisdom of a mature mind. It is a work in which the author attempted to conciliate two conflicting theories of knowledge current at his time: British empiricism as represented by John Locke, George Berkeley, and David Hume, and continental rationalism as represented by René Descartes, Gottfried Wilhelm Leibniz, and Christian von Wolff. The latter theory maintained that important truths about the natural and the supernatural worlds are knowable by pure reason alone, independently of perceptual experience, whereas the former held that perceptual experience is the source of all our legitimate concepts and truths of the world. Kant believed that both these doctrines were wrong, and he tried in Critique of Pure Reason to correct the pretensions of each while saving what was sound in each.


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