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Kant, Immanuel (1724–1804)

DOI
10.4324/9780415249126-DB047-2
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Published
2004
DOI: 10.4324/9780415249126-DB047-2
Version: v2,  Published online: 2004
Retrieved February 20, 2019, from https://www.rep.routledge.com/articles/biographical/kant-immanuel-1724-1804/v-2

4. The project of the Critique of Pure Reason

In spite of this progress in 1775, six more years passed before the Critique of Pure Reason finally appeared in 1781. In an umistakeable reference to Locke’s Essay concerning Human Understanding (see Locke, J.), Kant began the work with the promise to submit reason to a critique in order to obtain a ‘decision about the possibility or impossibility of metaphysics in general and the determination of its sources, its scope and its boundaries’ (A xii). The ‘chief question’ would be ‘what and how much can understanding and reason know apart from all experience?’ (A xvii). Answering this question would require discovering the fundamental principles that human understanding contributes to human experience and exposing the metaphysical illusions that arise when human reason tries to extend those principles beyond the limits of human experience.

But Kant’s project was even more ambitious than that, as he was to make clear in the revised edition of the Critique six years later. There, in addition to more explicitly describing his strategy for explaining the certainty of the first principles of human knowledge as one of supposing that ‘objects must conform to our knowledge’ rather than vice versa (B xvi), Kant described his whole project in broader terms: ‘I therefore had to deny knowledge in order to make room for faith’ (B xxx). Kant did not mean to return to the sceptical fideism of earlier thinkers such as Pierre Bayle, who simply substituted religious belief for theoretical ignorance. Instead, Kant argues first that the human mind supplies necessary principles of sensibility and understanding, or perception and conception; next, that if human reason tries to extend the fundamental concepts and principles of thought beyond the limits of perception for purposes of theoretical knowledge, it yields only illusion; but finally that there is another use of reason, a practical use in which it constructs universal laws and ideals of human conduct and postulates the fulfilment of the conditions necessary to make such conduct rational, including the freedom of the will, the existence of God, and the immortality of the soul. This use of reason does not challenge the limits of theoretical reason but is legitimate and necessary in its own right.

In the Introduction, Kant defines his first task as that of explaining the possibility of synthetic a priori judgments. This notion is grounded in two distinctions. First, there is a logical distinction between analytic and synthetic propositions: in analytic propositions, the predicate-concept is implicitly or explicitly contained in the subject-concept (for example, ‘A bachelor is unmarried’ or ‘An unmarried male is male’), so the proposition conveys no new information and is true by identity alone; in synthetic propositions, the content of the predicate is clearly not contained in the subject-concept (for example, ‘Bachelors are unhappy’) (A 6–7/B 10–11), so the proposition conveys new information and cannot be true by identity alone. Second, there is an epistemological distinction between propositions which are a posteriori, or can be known to be true only on the basis of antecedent experience and observation, and those which are a priori, or known to be true independently of experience, or at least any particular experience (A 1–2/B 1–3). Kant maintains that anything which is known to be universally and necessarily true must be known a priori, because, following Hume, he assumes that experience only tells us how what has actually been observed is, not how everything must be (A 1–2/B 3–4). Combining these two distinctions yields four possible kinds of judgments. Two of these obviously obtain: analytic a priori judgments, in which we know a proposition to be true by analysis of its subject-concept and without observation; and synthetic a posteriori judgments, in which we know factual statements going beyond subject-concepts to be true through observation. Equally clearly, a third possibility is excluded: there are no analytic a posteriori judgments, for we need not go to experience to discover what we can know from analysis alone. What is controversial is whether there are synthetic a priori judgments, propositions that are universally and necessarily true, and thus must go beyond experience, but which cannot be reached by the mere analysis of concepts. Both rationalists and empiricists had denied such a possibility, but for Kant only it could ground an informative science of metaphysics at all.

Kant’s notion of synthetic a priori judgment raises various problems. Critics have long complained that Kant provides no unequivocal criterion for deciding when a predicate is contained in a subject, and twentieth-century philosophers such as W. Quine argued that there are no analytic truths because not even definitions can be held entirely immune from revision in the face of empirical facts. Lewis White Beck showed, however, that this did not affect Kant’s project, for Kant himself, in a polemic with the Wolffian Johann August Eberhard, argued that analysis always presupposes synthesis, and that the adoption of any definition itself has to be justified, either by construction or observation; so even conceding that all judgments are ultimately synthetic, Kant’s question remains whether any of these are synthetic a priori.

Another issue is just what synthetic a priori judgments Kant intended to justify. In the ‘Prolegomena’ and the ‘Introduction’ to the second edition of the Critique, Kant suggests that it is obvious that synthetic a priori judgments exist in what he calls ‘pure mathematics’ and ‘pure physics’, and that his project is to show that what explains these also explains other such propositions, in metaphysics. Elsewhere, however, Kant suggests that metaphysics must show that there are any synthetic a priori judgments, even in mathematics and physics. While much of the content of the Critique suggests that Kant’s considered view must be the latter, he is far from clear about this.

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Citing this article:
Guyer, Paul. The project of the Critique of Pure Reason. Kant, Immanuel (1724–1804), 2004, doi:10.4324/9780415249126-DB047-2. Routledge Encyclopedia of Philosophy, Taylor and Francis, https://www.rep.routledge.com/articles/biographical/kant-immanuel-1724-1804/v-2/sections/the-project-of-the-critique-of-pure-reason.
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