Immanuel Kant revolutionized philosophy by asking and answering the seemingly simple question, “How is knowledge possible?” His Critique of Pure Reason is among the most important texts in the history of philosophy, as it is the starting point for both the analytic and continental traditions that followed.

The continental rationalism Rationalism that René Descartes pioneered in the 1630’s culminated in the elaborate philosophical vision of Gottfried Wilhelm Leibniz. Starting around 1709, Christian Wolff built an internally coherent and overarching philosophical system based mainly on Leibniz’s principle of sufficient reason, Principle of sufficient reason
Reason;and German philosophy[German philosophy] the idea that anything that exists must necessarily have some reason why it exists. Wolff intended this system to be the last word in philosophy, and for a time he was successful. [kw]Kant Publishes Critique of Pure Reason (1781)
[kw]Reason, Kant Publishes Critique of Pure (1781)
[kw]Critique of Pure Reason, Kant Publishes (1781)
[kw]Publishes Critique of Pure Reason, Kant (1781)
Critique of Pure Reason (Kant)
Transcendental philosophy
Kant’s First Critique[Kants First Critique]
[g]Prussia;1781: Kant Publishes Critique of Pure Reason[2430]
[g]Germany;1781: Kant Publishes Critique of Pure Reason[2430]
[g]Russia;1781: Kant Publishes Critique of Pure Reason[2430]
[c]Philosophy;1781: Kant Publishes Critique of Pure Reason[2430]
[c]Literature;1781: Kant Publishes Critique of Pure Reason[2430]
Kant, Immanuel
Baumgarten, Alexander Gottlieb
Descartes, René
Fichte, Johann Gottlieb
Hegel, Georg Wilhelm Friedrich
Hume, David
Leibniz, Gottfried Wilhelm
Schelling, Friedrich Wilhelm Joseph von
Wolff, Christian

By the mid-eighteenth century, the Leibniz-Wolff Leibniz-Wolff school of metaphysics[Leibniz Wolff] system had become the standard curriculum in German universities and secondary schools. Its effect on German thought was at once stimulating, because of its wide scope, and smothering, because of its pretensions of inclusiveness, closure, and finality. Among the Leibniz-Wolffians was Alexander Gottlieb Baumgarten, whose metaphysics and philosophy of art strongly influenced Immanuel Kant.

Kant claimed in 1783 that reading David Hume Hume, David in the 1760’s or 1770’s had awakened him from the “dogmatic slumber” that had been induced by immersion in the Leibniz-Wolff school of metaphysics. Metaphysics Kant’s new doubts about Leibniz-Wolff pushed him toward unprecedented critical inquiry. He began to ask questions that were more fundamental and potentially more unsettling than any questions asked by the continental rationalists. Kant published his answers to these questions about the very nature of knowing as Kritik der reinen Vernunft (1781; Critique of Pure Reason, 1838). His purpose in this massive, difficult, and supremely important book was to determine which logical, metaphysical, or transcendental conditions are absolutely necessary for any knowledge, especially a priori knowledge, A priori knowledge (Kant)
Knowledge, a priori
Epistemology;a priori knowledge to arise. He called the book Critique of Pure Reason because pure reason is supposed to be that faculty which alone is capable of a priori knowledge.

Kant’s philosophy, although systematic, is critical and exploratory rather than dogmatic and didactic. He attacked rationalism by saying that concepts without percepts are empty, attacked empiricism by saying that percepts without concepts are blind, and sought a synthetic middle ground in which rationalism and empiricism would take each other seriously. He considered his inquiry “transcendental,” that is, concerned not with the knowledge of the usual objects of knowledge, but with the a priori knowledge of how the knowledge of objects is possible. Accordingly, the book is divided into sections such as “Transcendental Aesthetic,” considering how sensation is possible; “Transcendental Logic,” considering how concepts, intuitions, and thinking itself are possible; “Transcendental Analytic,” considering how understanding is possible; and “Transcendental Dialectic,” considering how the generation of new ideas is possible.

The transcendental aesthetic Aesthetics;Kantian posits the two forms of intuition, space and time, Space and time
Time and space through which all perception Perception must occur. The transcendental analytic, as part of the transcendental logic, Logic offers an exhaustive table of twelve kinds of judgments in four groups of three. Under “Quantity” are universal, particular, and singular judgments; under “Quality” are affirmative, negative, and infinite; under “Relation” are categorical, hypothetical, and disjunctive; and under “Modality” are problematic, assertive, and certain. This table corresponds to the twelve “pure concepts” or categories of the understanding, also divided into four groups of three. Under “Quantity” are unity, plurality, and totality; under “Quality” are reality, negation, and limitation; under “Relation” are substance/accident, cause/effect, and community; and under “Modality” are possibility/impossibility, existence/nonexistence, and necessity/contingency. Rational consciousness, and therefore human understanding, is internally coherent through what Kant calls “the transcendental unity of apperception.” This self-consciousness defines not only the human self, but also any other possible rational selves of any other species that may exist anywhere in the universe.

The transcendental dialectic, Dialectics as the other part of the logic, examines some of the consequences and paradoxes of pure reason. Central to this section are the antinomies, four examples of how conflicts in dogma, when argued out to their logical conclusions, result in unresolvable contradictions. The dialectic also examines difficult questions about God, freedom, and immortality, and challenges the traditional theistic proofs.

For Kant as for the continental rationalists, mathematics Mathematics;and Kantian philosophy[Kantian philosophy] is the epitome of clear and rational knowledge. All that is empirically Empiricism
Experience and knowledge knowable is phenomenon Reality and philosophy
Philosophy;and reality[reality] or appearance, that is, the way that things appear to perceivers. Appearances are not true reflections of reality. Kant posited that behind every appearance is an unknowable and unreachable noumenon or thing-in-itself. Thing-in-itself (Kant)[Thing in itself] However, the truths of mathematics are knowable, reachable, and synthetic a priori because they emerge from the application of pure reason alone without recourse to experience. Kant aimed in the Critique of Pure Reason to establish synthetic a priori knowledge for other fields besides mathematics. Philosophers continue to debate whether he achieved this goal.

Kant published two other critiques, Kritik der praktischen Vernunft (1788; Critique of Practical Reason, Critique of Practical Reason (Kant) 1873), which grounds social, ethical, and political philosophy, and Kritik der Urteilskraft (1790; The Critique of Judgment, Critique of Judgment, The (Kant) 1892), which develops a philosophy of art. Philosophers typically refer to these books as Kant’s First, Second, and Third Critiques. Kant’s other major work, Grundlegung zur Metaphysik der Sitten (1785; Fundamental Principles of the Metaphysics of Ethics, 1895; better known as Foundations of the Metaphysics of Morals, Foundations of the Metaphysics of Morals (Kant) 1950), introduced to ethics the concept of the categorical imperative, Categorical imperative or an objectively valid moral law that holds in all circumstances. All three of these later works, especially the Foundations of the Metaphysics of Morals, depend upon the principle of freedom as established in the First Critique. Kant defines freedom as the ability of an agent to be an unconditioned cause of some event, which makes freedom an absolutely necessary precondition for any human thought, action, judgment, morality, or ethics.

Kant’s influence on philosophy is immeasurable. Along with Plato, Aristotle, Thomas Aquinas, Descartes, Baruch Spinoza, Hume, Georg Wilhelm Friedrich Hegel, Friedrich Nietzsche, Martin Heidegger, and Ludwig Wittgenstein, he is acknowledged as one of the greatest philosophers of all time. Greatness in philosophy involves innovation, intelligence, coherence, discernment, and relevance. Kant’s writings all show these qualities in abundance.

It is not an exaggeration to argue that, without Kant’s insights, the course of subsequent philosophy would not have been possible. Within two decades after the publication of his first critique, reaction against his concept of the thing-in-itself had sown the seeds of German Idealism Idealism
German Idealism in Johann Gottlieb Fichte, Friedrich Wilhelm Joseph von Schelling, and Hegel. German Idealism was the first major post-Kantian movement in philosophy that would not have been possible without Kant.

Kantians generally divide into two camps, those who see him as essentially a metaphysician and those who use his thought as the foundation of analytic philosophy. Analytic philosophy
Philosophy;analytic We might call these camps rationalist and empiricist, respectively, but, like most philosophical labeling, this is problematic. Kant aimed to synthesize rationalism and empiricism, and perhaps to some extent succeeded, but the point is that neither rationalism nor empiricism could have proceeded into the nineteenth century without considering Kant. Continental European speculative thinkers who are concerned with overarching truths and British-American philosophers who prefer the minute analysis and clarification of language and logic equally take their direction from Kant.

• Adorno, Theodor. Kant’s “Critique of Pure Reason.” Stanford, Calif.: Stanford University Press, 2001. An engaging work by a major twentieth century German philosopher that tells as much about Adorno as it does about Kant.
• Dicker, Georges. Kant’s Theory of Knowledge: An Analytical Introduction. New York: Oxford University Press, 2004. A useful aid for first-time readers of the transcendental aesthetic, logic, and analytic.
• Gardner, Sebastian. Kant and the “Critique of Pure Reason.” New York: Routledge, 2000. A well-reviewed basic introduction to Kant in Routledge’s popular Philosophy Guidebooks series.
• Hanna, Robert. Kant and the Foundations of Analytic Philosophy. New York: Oxford University Press, 2004. Defends Kant against several kinds of criticism.
• Hartnack, Justus. Kant’s Theory of Knowledge: An Introduction to the “Critique of Pure Reason.” Indianapolis, Ind.: Hackett, 2001. A classic short introduction.
• Kant, Immanuel. Critique of Pure Reason. Translated by Norman Kemp Smith. New York: St. Martin’s Press, 1965. The standard English translation.
• Kuehn, Manfred. Kant: A Biography. New York: Cambridge University Press, 2001. A commendable focus on the chronological development of Kant’s ideas, rather than on his uneventful life.
• Sassen, Brigitte, ed. Kant’s Early Critics: The Empiricist Critique of the Theoretical Philosophy. New York: Cambridge University Press, 2000. Even though fixed on the empiricist contribution to the philosophical dialogue, Sassen identifies three strains of German comment on Kant during his lifetime: empiricist, rationalist, and idealist.
• Savile, Anthony. Kant’s “Critique of Pure Reason”: An Orientation to the Central Theme. Malden, Mass.: Blackwell, 2005. A penetrating analysis by a renowned expert on Kant, continental rationalism, and eighteenth century aesthetics.
• Sedgwick, Sally S., ed. The Reception of Kant’s Critical Philosophy: Fichte, Schelling, and Hegel. New York: Cambridge University Press, 2000. A solid collection of new interpretations by world-class scholars.
• Smith, Norman Kemp. A Commentary to Kant’s “Critique of Pure Reason.” New York: Palgrave Macmillan, 2003. The standard commentary and an important key to Kant’s difficult work.

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Johann Gottlieb Fichte; David Hume; Immanuel Kant. Critique of Pure Reason (Kant)
Transcendental philosophy
Kant’s First Critique[Kants First Critique]