The major works of the German philosopher Immanuel Kant (1724-1804) offer an analysis of speculative and moral reason and the faculty of human judgment. He exerted an immense influence on the intellectual movements of the 19th and 20th centuries.
The fourth of nine children of Johann Georg and Anna Regina Kant, Immanuel Kant was born in the town of Königsberg on April 22, 1724. Johann Kant was a harness maker, and the large family lived in modest circumstances. The family belonged to a Protestant sect of Pietists, and a concern for religion touched every aspect of their lives. Although Kant became critical of formal religion, he continued to admire the "praiseworthy conduct" of Pietists. Kant's elementary education was taken at Saint George's Hospital School and then at the Collegium Fredericianum, a Pietist school, where he remained from 1732 until 1740.
In 1740 Kant entered the University of Königsberg. Under the influence of a young instructor, Martin Knutzen, Kant became interested in philosophy, mathematics, and the natural sciences. Through the use of Knutzen's private library, Kant grew familiar with the philosophy of Christian Wolff, who had systematized the rationalism of Leibniz. Kant accepted the rationalism of Leibniz and Wolff and the natural philosophy of Newton until a chance reading of David Hume aroused him from his "dogmatic slumbers."
The death of Kant's father in 1746 left him without income. He became a private tutor for 7 years in order to acquire the means and leisure to begin an academic career. During this period Kant published several papers dealing with scientific questions. The most important was the "General Natural History and Theory of the Heavens" in 1755. In this work Kant postulated the origin of the solar system as a result of the gravitational interaction of atoms. This theory anticipated Laplace's hypothesis (1796) by more than 40 years. In the same year Kant presented a Latin treatise, "On Fire", to qualify for the doctoral degree.
Kant spent the next 15 years (1755-1770) as a nonsalaried lecturer whose fees were derived entirely from the students who attended his lectures. In order to live he lectured between 26 and 28 hours a week on metaphysics, logic, mathematics, physics, and physical geography. Despite this enormous teaching burden, Kant continued to publish papers on various topics. He finally achieved a professorship at Königsberg in 1770.
Critique of Pure Reason
For the next decade Kant published almost nothing. But at the age of 57 he published the first edition of the Critique of Pure Reason (1781; 2d ed. 1787). This enormous work, one of the most important and difficult books in Western thought, attempts to resolve the contradictions inherent in perception and conception as explained by the rationalists and empiricists.
On the level of experience, Kant saw the inherent difficulties in the "representative theory of perception." Our percepts, or intuitions of things, are not themselves objects but rather images or re-presentations. Since these perceptual images are the only evidence for an external, physical world, it can be asked how faithfully mental images represent physical objects. On the level of conception, mathematical, scientific, and metaphysical judgments make predictions about the connections and consequences of events. As these judgments tell us about the past, present, and future, they cannot be derived from our immediate experience. Some events, however, can be experienced as conforming to these universal and necessary laws; hence, these judgments are more than mere definitions. The aim of the critique is to explain how experience and reason interact in perception and understanding.
Philosophers had long recognized two kinds of judgment. The first is analytic, which is the product of the analysis or definition of concepts. All analytic propositions are reducible to statements of identity, that is, they define what a thing is. For example, a triangle is a three-sided figure universally (always) and necessarily (could not be otherwise) by definition. As such, all analytic judgments are true a priori, or independent of experience. The content and form of the second type of judgment is exactly the reverse. Synthetic propositions expand or amplify our knowledge, but these judgments are a posteriori, or derived from experience.
Kant's position is that of the first thinker to posit the problem of pure reason correctly by isolating a third order of judgment. Consider the following propositions: 10 times 2 is 20; every event has a cause; the universe is created. As universal and necessary, all three judgments are a priori but also, according to Kant, synthetic, in that they extend our knowledge of reality. Thus the fundamental propositions of mathematics, science, and metaphysics are synthetic a priori, and the question that the Critique of Pure Reason poses is not an analysis of whether there is such knowledge but a methodology of how "understanding and reason can know apart from experience."
The solution to this problem is Kant's "Copernican Revolution." Until Copernicus hypothesized that the sun was the center of the universe and the earth in its rotation, science had assumed the earth was the center of the universe. Just so, argues Kant, philosophers have attempted and failed to prove that our perceptions and judgments are true because they correspond to objects. "We must therefore make trial whether we may not have more success…ifwe suppose that objects must conform to our knowledge." This radical proposal means that the mind constitutes the way the world appears and the way in which the world is thought about.
But, unlike later idealists, Kant does not say that the mind creates objects but only the conditions under which objects are perceived and understood. According to Kant, "we can know a priori of things only what we ourselves put into them." The attempt to preserve a realist orientation leads Kant to distinguish between the appearances of things (phenomena), as conditioned by the subjective forms of intuition, and the categories of the understanding and things-in-themselves (noumena). In brief, mathematics and science are true because they are derived from the ways in which the mind conditions its percepts and concepts, and metaphysics is an illusion because it claims to tell us about things as they really are. But since the mind constitutes the appearances and their intelligibility, we can never know noumenal reality (as it exists apart from mind) with any certainty. Although Kant considers the denial of metaphysics inconsequential because it has consisted only of "mock combats" in which no victory was ever gained, he is at some pains to establish that the restriction of pure reason to the limits of sensibility does not preclude a practical knowledge of morality and religion. In fact, the limitation of pure reason makes such faith more positive.
The first critique attempts to reconcile the conflict between rationalism and empiricism over the role of experience. Kant's ingenuity is to suggest that both parties are correct but one-sided, that is, "though all knowledge begins with experience it does not follow that it arises out of experience." Kant attempts to isolate the a priori element in the various parts of knowledge: intuition, which Kant calls esthetic, understanding, or analytic and speculative reason, or dialectic. He calls his method "transcendental" as opposed to formal or material logic, and by this he means only the manner, or mode, in which we perceive, understand, or think.
The problem of the transcendental esthetic can be seen in the term "a priori intuition." That is, what does the mind tell us about experience prior to having experience. Kant argues that if one eliminates the content of any possible intuition, space and time remain as the a priori forms, or ways, in which the mind can perceive. As a priori forms of any possible experience, space and time are subjective conditions or limitations of human sensibility. But as the universal and necessary conditions without which there will be no experience, these forms are empirical conditions of appearances, or phenomena. Thus, for Kant, space and time are "transcendentally ideal" and "empirically real" as subjective conditions and objective, constitutive principles of intuition. In brief, this is Kant's resolution of the scientific debate between the adherents of Newton's concept of absolute space and time and Leibniz's relational view. Kant is saying that space and time are absolute conditions for human experience even though there may be nonspatial and nontemporal entities that are unknown.
This argument provides an answer to how synthetic a priori judgments in mathematics are possible. These judgments are universal and necessary, and yet they apply to and yield new knowledge about experience. The principle of Kant's explanation may be expressed as follows: whatever is true of a condition is a priori true of the conditioned. Space and time are the conditions for all possible perceptions. And Euclidean geometry and arithmetic are true of space and time. Therefore, arithmetic and geometry are a priori valid for all possible appearances.
A weak analogy with eyeglasses will explain the drift of Kant's thinking. If I cannot see anything without the glasses, they are my subjective limitation since there may be things which are not perceivable. But the glasses are also objective conditions for the possibility of anything appearing to me. And whatevers true of this condition—such as their being tinted—will be true a priori of whatever can be seen but not necessarily of whatever can be. The point of Kant's radical proposal is that human experience may be just that— exclusively human—but that it is valid of appearances since space and time are the a priori and empirical conditions of every possible perception.
A similar explanation of the working of human understanding presented a great difficulty occasioned by the seeming impossibility of specifying the forms of thinking in other than an arbitrary and chance manner. Eventually Kant discovered a "transcendental clue" in the traditional forms of logical judgment enumerated by Aristotle. The question raised is why are there only 12 forms of judgment? Kant argued that each form of possible judgment was related to a thought form that he called an a priori category of the understanding. Thus, again, there is a form and content division such that, if one thinks, there are only certain ways in which one can make judgments about the quantity, quality, relation, and modality of objects. In human understanding, as the name implies, experience is made to stand underneath and be organized by the categories. Experience is given as conditioned by space and time, a category is superimposed by the mind, and the resulting synthesis produces human knowing. This complicated process of synthesis is unified by the ego and aided by the imagination, which associates particular percepts with appropriate universal concepts. As in the case of perception, Kant's efforts are directed toward reconciling the claims of both rationalism and empiricism. Concepts of themselves are empty logical forms, and percepts, alone, are blind; it is only in their synthesis that understanding, or knowing, takes place.
This development commits Kant to the position that science is knowing and metaphysics is false, speculative thinking. Knowing is confirmed by experience as above, but the categories can be extended beyond space and time, and they, then, function as ideas of pure reason. Since metaphysics claims to speak about things as they are rather than as they appear, such pure thinking must justify itself without appeal to experience. But that is just the difficulty when one asks questions about the unconditioned reality of the self, world, or God!
It is not that reason is incapable of producing arguments, but rather that there are equally valid arguments that contradict one another, and experience is unable to resolve these "antinomies," or seeming contradictions. For example, we know that the universe is either created or eternal, and we can think both of these alternatives through; but the spatiotemporal world of experience would be the same in either instance; and so while the mind can think about these problems, it can never know the answers to the questions that it raises. The only exception to this rule occurs in what Kant calls the "dynamical antinomies" concerning the dilemmas of necessity or freedom and atheism or theism. Here Kant suggests that in the realms of morality and religion one can entertain the possibility that while necessity and determinism are true of phenomena, freedom and God are true of noumena. Thus, one could live in a universe that is physically determined and still believe in human freedom.
In 1783 Kant restated the main outlines of his first critique in a brief, analytic form in the Prolegomena to Any Future Metaphysics. In 1785 he presented an early view of the practical aspects of reason in Fundamental Principles of the Metaphysic of Morals. In 1788 he published the Critique of Practical Reason.
While theoretical reason is concerned with cognition, practical reason is concerned with will, or self-determination. There is only one human reason, but after it decides what it can know, it must determine how it shall act. In the analytic of practical reason Kant attempts to isolate the a priori element in morality. The notion that happiness is the end of life is purely subjective, and every empirical morality is arbitrary.
Thus the freedom of the will, which is only a speculative possibility for pure reason, becomes the practical necessity of determining how one shall lead his life. And the fundamental, rational principle of a free morality is some universal and necessary law to which a man commits himself. This principle is called by Kant the "Categorical Imperative," which states that a man should obligate himself to act so that any one of his actions could be made into a universal law binding all mankind. The dignity of man consists in the freedom to overcome inclination and private interest in order to obligate oneself to the duty of performing the good for its own sake. In examining the consequences of man's freedom, Kant insists that practical reason postulates the immortality of the soul and the existence of God as the conditions for true freedom.
In 1790 Kant completed his third critique, which attempts to draw these conflicting tensions together. In pure reason the mind produces constitutive principles of phenomena, and in practical reason the mind produces regulative principles of noumenal reality. The Critique of Judgment attempts to connect the concepts of nature with the concepts of freedom. The reflective or teleological judgment of finality, which is derived from our esthetic feelings about the fittingness of things, mediates between our cognition and our will. This judgment neither constitutes nature like the understanding nor legislates action like practical reason, but it does enable us to think of the "purposiveness" of nature as a realm of ends that are in harmony with universal laws.
Although Kant continued writing until shortly before his death, the "critical works" are the source of his influence. Only a life of extraordinary self-discipline enabled him to accomplish his task. He was barely 5 feet tall and extremely thin, and his health was never robust. He attributed his longevity to an invariable routine. Rising at five, he drank tea and smoked his daily pipe and meditated for an hour. From six to seven he prepared his lectures and taught from seven to nine in his own home. He worked in his study until one. He invited friends for long dinners, which lasted often until four. After his one daily meal he walked between four and five so punctually that people were said to set their watches on his passing. He continued to write or read until he retired at ten. Toward the end of his life he became increasingly antisocial and bitter over the growing loss of his memory and capacity for work. Kant became totally blind and finally died on Feb. 12, 1804.
Further Reading on Immanuel Kant
There is no standard edition in English, but virtually all of Kant's major works are available in various paperback editions. The field of general and critical studies is rich. Basic accounts of Kant's critique are Herbert James Paton, Kant's Metaphysic of Experience (2 vols., 1936); Heinrick Cassirer, A Commentary on Kant's Critique of Judgment (1938); A. C. Ewing, A Commentary on Kant's Critique of Pure Reason (1938); Lewis White Beck, A Commentary on Kant's Critique of Practical Reason (1960); Norman Kemp Smith, A Commentary to Kant's Critique of Pure Reason (2d ed. 1962); and S. Körner, Kant (1964), which is one of the best general works available. Specialized studies include Paul Arthur Schlipp, Kant's Pre-critical Ethics (2d ed. 1960); Martin Heidegger, Kant and the Problem of Metaphysics, translated by James S. Churchill (1962); Robert Paul Wolff, Kant's Theory of Mental Activity (1963); and P. F. Strawson, The Bounds of Sense (1966).