Immanuel Kant (22 April 1724 12 February 1804) was an 18th-century German philosopher from the Prussian city of Königsberg (now Kaliningrad, Russia). He is regarded as one of the most influential thinkers of modern Europe and of the late Enlightenment.
His most important work is the Critique of Pure Reason, a critical investigation of reason itself. It encompasses an attack on traditional metaphysics and epistemology, and highlights Kant's own contribution to these areas. The other main works of his maturity are the Critique of Practical Reason, which concentrates on ethics, and the Critique of Judgement, which investigates aesthetics and teleology.
Pursuing metaphysics involves asking questions about the ultimate nature of reality. Kant suggested that metaphysics can be reformed through epistemology. He suggested that by understanding the sources and limits of human knowledge we can ask fruitful metaphysical questions. He asked if an object can be known to have certain properties prior to the experience of that object. He concluded that all objects that the mind can think about must conform to its manner of thought. Therefore if the mind can only think in terms of causality which he concluded that it does then we can know prior to experiencing them that all objects we experience must either be a cause or an effect. However, it follows from this that it is possible that there are objects of such a nature that the mind cannot think of them, and so the principle of causality, for instance, cannot be applied outside of experience: hence we cannot know, for example, whether the world always existed or if it had a cause. And so the grand questions of speculative metaphysics are off limits, but the sciences are firmly grounded in laws of the mind.
Kant believed himself to be creating a compromise between the empiricists and the rationalists. The empiricists believed that knowledge is acquired through experience alone, but the rationalists maintained that such knowledge is open to Cartesian doubt and that reason alone provides us with knowledge. Kant argues, however, that using reason without applying it to experience will only lead to illusions, while experience will be purely subjective without first being subsumed under pure reason.
Kant’s thought was very influential in Germany during his lifetime, moving philosophy beyond the debate between the rationalists and empiricists. The philosophers Fichte, Schelling, Hegel and Schopenhauer saw themselves as correcting and expanding the Kantian system, thus bringing about various forms of German Idealism. Kant continues to be a major influence on philosophy to this day, influencing both Analytic and Continental Philosophy.
In the General History of Nature and Theory of the Heavens (Allgemeine Naturgeschichte und Theorie des Himmels) (1755), Kant laid out the Nebular Hypothesis, in which he deduced that the Solar System formed from a large cloud of gas, a nebula. He thus attempted to explain the order of the solar system, seen previously by Newton as being imposed from the beginning by God. Kant also correctly deduced that the Milky Way was a large disk of stars, which he theorized also formed from a (much larger) spinning cloud of gas. He further suggested the possibility that other nebulae might also be similarly large and distant disks of stars. These postulations opened new horizons for astronomy: for the first time extending astronomy beyond the solar system to galactic and extragalactic realms.
From this point on, Kant turned increasingly to philosophical issues, although he continued to write on the sciences throughout his life. In the early 1760s, Kant produced a series of important works in philosophy. The False Subtlety of the Four Syllogistic Figures, a work in logic, was published in 1762. Two more works appeared the following year: Attempt to Introduce the Concept of Negative Magnitudes into Philosophy and The Only Possible Argument in Support of a Demonstration of the Existence of God. In 1764, Kant wrote Observations on the Feeling of the Beautiful and Sublime and then was second to Moses Mendelssohn in a Berlin Academy prize competition with his Inquiry Concerning the Distinctness of the Principles of Natural Theology and Morality (often referred to as "the Prize Essay"). In 1770, at the age of 45, Kant was finally appointed Professor of Logic and Metaphysics at the University of Königsberg. Kant wrote his Inaugural Dissertation in defense of this appointment. This work saw the emergence of several central themes of his mature work, including the distinction between the faculties of intellectual thought and sensible receptivity. Not to observe this distinction would mean to commit the error of subreption, and, as he says in the last chapter of the dissertation, only in avoidance of this error will metaphysics flourish.
The issue that vexed Kant was central to what twentieth century scholars termed "the philosophy of mind." The flowering of the natural sciences had led to an understanding of how data reaches the brain. Sunlight may fall upon a distant object, whereupon light is reflected from various parts of the object in a way that maps the surface features (color, texture, etc.) of the object. The light reaches the eye of a human observer, passes through the cornea, is focused by the lens upon the retina where it forms an image similar to that formed by light passing through a pinhole into a camera obscura. The retinal cells next send impulses through the optic nerve and thereafter they form a mapping in the brain of the visual features of the distant object. The interior mapping is not the exterior thing being mapped, and our belief that there is a meaningful relationship between the exterior object and the mapping in the brain depends on a chain of reasoning that is not fully grounded. But the uncertainty aroused by these considerations, the uncertainties raised by optical illusions, misperceptions, delusions, etc., are not the end of the problems.
Kant saw the mind could not function as an empty container that simply receives data from the outside. Something had to be giving order to the incoming data. Images of external objects have to be kept in the same sequence in which they were received. This ordering occurs through the mind's intuition of time. The same considerations apply to the mind's function of constituting space for ordering mappings of visual and tactile signals arriving via the already described chains of physical causation.
Kant spent his silent decade working on a solution to the problem mentioned above. Although fond of company and conversation with others, Kant isolated himself. He resisted friends' attempts to bring him out of his isolation. In 1778, in response to one of these offers by a former pupil, Kant wrote "Any change makes me apprehensive, even if it offers the greatest promise of improving my condition, and I am persuaded by this natural instinct of mine that I must take heed if I wish that the threads which the Fates spin so thin and weak in my case to be spun to any length. My great thanks, to my well-wishers and friends, who think so kindly of me as to undertake my welfare, but at the same time a most humble request to protect me in my current condition from any disturbance.
When Kant emerged from his silence in 1781, the result was the Critique of Pure Reason. Although now uniformly recognized as one of the greatest works in the history of philosophy, this Critique was largely ignored upon its initial publication. The book was long, over 800 pages in the original German edition, and written in what some considered a convoluted style. It received few reviews, and these granted no significance to the work. Its density made it, as Johann Gottfried Herder put it in a letter to Johann Georg Hamann, a "tough nut to crack," obscured by "…all this heavy gossamer. Its reception stood in stark contrast, to the praise Kant had received for earlier works such as his "Prize Essay" and other shorter works that precede the first Critique. These well-received and readable tracts include one on the earthquake in Lisbon which was so popular that it was sold by the page. Prior to the change in course documented in the first Critique, his books sold well, and by the time he published Observations On the Feeling of the Beautiful and the Sublime in 1764 he had become a popular author of some note. Kant was disappointed with the first Critique's reception. Recognizing the need to clarify the original treatise, Kant wrote the Prolegomena to any Future Metaphysics in 1783 as a summary of its main views. He also encouraged his friend, Johann Schultz, to publish a brief commentary on the Critique of Pure Reason.
Kant's reputation gradually rose through the 1780s, sparked by a series of important works: the 1784 essay, "Answer to the Question: What is Enlightenment?"; 1785s Groundwork of the Metaphysics of Morals (his first work on moral philosophy); and, from 1786, Metaphysical Foundations of Natural Science. But Kant's fame ultimately arrived from an unexpected source. In 1786, Karl Reinhold began to publish a series of public letters on the Kantian philosophy. In these letters, Reinhold framed Kant's philosophy as a response to the central intellectual controversy of the era: the Pantheism Dispute. Friedrich Jacobi had accused the recently deceased G. E. Lessing (a distinguished dramatist and philosophical essayist) of Spinozism. Such a charge, tantamount to atheism, was vigorously denied by Lessing's friend Moses Mendelssohn, and a bitter public dispute arose among partisans. The controversy gradually escalated into a general debate over the values of the Enlightenment and the value of reason itself. Reinhold maintained in his letters that Kant's Critique of Pure Reason could settle this dispute by defending the authority and bounds of reason. Reinhold's letters were widely read and made Kant the most famous philosopher of his era.
Kant never concluded that one could form a coherent account of the universe and of human experience without grounding such an account in the "thing in itself." Many of those who followed him argued that since the "thing in itself" was unknowable its existence could not simply be assumed. Rather than arbitrarily switching to an account that was ungrounded in anything supposed to be the "real," as did the German Idealists, another group arose to ask how our (generally reliable) accounts of a coherent and rule-abiding universe were actually grounded. This new kind of philosophy became known as Phenomenology, and its preeminent spokesman was Edmund Husserl.
A variety of popular beliefs have arisen concerning Kant's life. It is often held, for instance, that Kant was a late bloomer, that he only became an important philosopher in his mid-50s after rejecting his earlier views. While it is true that Kant wrote his greatest works relatively late in life, there is a tendency to underestimate the value of his earlier works. Recent Kant scholarship has devoted more attention to these "pre-critical" writings and has recognized a degree of continuity with his mature work.
Many of the common myths concerning Kant's personal mannerisms are enumerated, explained, and refuted in Goldwaite's introduction to his translation of Observations on the Feeling of the Beautiful and Sublime. It is often held that Kant lived a very strict and predictable life, leading to the oft-repeated story that neighbors would set their clocks by his daily walks. He never married and probably died a virgin . Only later in his life, under the influence of his friend, the English merchant Joseph Green, did Kant adopt a more regulated lifestyle.
Kant asserted that, because of the limitations of argumentation in the absence of irrefutable evidence, no one could really know whether there is a God and an afterlife or not, and, conversely, that no one could really know that there is no God and no afterlife. For the sake of society and morality, Kant asserted, people are reasonably justified in believing in them, even though they could never know for sure whether they are real or not. He explained:
The sense of an enlightened approach and the critical method required that "If one cannot prove that a thing is, he may try to prove that it is not. And if he succeeds in doing neither (as often occurs), he may still ask whether it is in his interest to accept one or the other of the alternatives hypothetically, from the theoretical or the practical point of view. Hence the question no longer is as to whether perpetual peace is a real thing or not a real thing, or as to whether we may not be deceiving ourselves when we adopt the former alternative, but we must act on the supposition of its being real." The presupposition of God, soul, and freedom was then a practical concern, for "Morality, by itself, constitutes a system, but happiness does not, unless it is distributed in exact proportion to morality. This, however, is possible in an intelligible world only under a wise author and ruler. Reason compels us to admit such a ruler, together with life in such a world, which we must consider as future life, or else all moral laws are to be considered as idle dreams… ."
The two interconnected foundations of what Kant called his "critical philosophy" that created the "Copernican revolution" that he claimed to have wrought in philosophy were his epistemology of Transcendental Idealism and his moral philosophy of the autonomy of practical reason. These teachings placed the active, rational human subject at the center of the cognitive and moral worlds. With regard to knowledge, Kant argued that the rational order of the world as known by science could never be accounted for merely by the fortuitous accumulation of sense perceptions. It was instead the product of the rule-based activity of "synthesis." This activity consisted of conceptual unification and integration carried out by the mind through concepts or the "categories of the understanding" operating on the perceptual manifold within space and time, which are not concepts, but are forms of sensibility that are a priori necessary conditions for any possible experience. Thus the objective order of nature and the causal necessity that operates within it are dependent upon the mind. There is wide disagreement among Kant scholars on the correct interpretation of this train of thought. The 'two-world' interpretation regards Kant's position as a statement of epistemological limitation, that we are never able to transcend the bounds of our own mind, meaning that we cannot access the "thing-in-itself". Kant, however, also speaks of the thing in itself or transcendental object as a product of the (human) understanding as it attempts to conceive of objects in abstraction from the conditions of sensibility. Following this line of thought, some interpreters have argued that the thing in itself does not represent a separate ontological domain but simply a way of considering objects by means of the understanding alone this is known as the two-aspect view. With regard to morality, Kant argued that the source of the good lies not in anything outside the human subject, either in nature or given by God, but rather is only the good will itself. A good will is one that acts from duty in accordance with the universal moral law that the autonomous human being freely gives itself. This law obliges one to treat humanity understood as rational agency, and represented through oneself as well as others as an end in itself rather than (merely) as means to other ends the individual might hold.
These ideas have largely framed or influenced all subsequent philosophical discussion and analysis. The specifics of Kant's account generated immediate and lasting controversy. Nevertheless, his theses that the mind itself necessarily makes a constitutive contribution to its knowledge, that this contribution is transcendental rather than psychological, that philosophy involves self-critical activity, that morality is rooted in human freedom, and that to act autonomously is to act according to rational moral principles have all had a lasting effect on subsequent philosophy.
Kant defines his theory of perception in his influential 1781 work The Critique of Pure Reason, which has often been cited as the most significant volume of metaphysics and epistemology in modern philosophy. Kant maintains that our understanding of the external world has its foundations not merely in experience, but in both experience and a priori concepts, thus offering a non-empiricist critique of rationalist philosophy, which is what he and others referred to as his "Copernican revolution.
Before discussing his theory, it is necessary to explain Kant's distinction between analytic and synthetic propositions.
Analytic propositions are true by nature of the meaning of the words involved in the sentence—we require no further knowledge than a grasp of the language to understand this proposition. On the other hand, synthetic statements are those that tell us something about the world. The truth or falsehood of synthetic statements derives from something outside of their linguistic content. In this instance, mass is not a necessary predicate of the body; until we are told the heaviness of the body we do not know that it has mass. In this case, experience of the body is required before its heaviness becomes clear. Before Kant's first Critique, empiricists (cf. Hume) and rationalists (cf. Leibniz) assumed that all synthetic statements required experience in order to be known.
Kant, however, contests this: he claims that elementary mathematics, like arithmetic, is synthetic a priori, in that its statements provide new knowledge, but knowledge that is not derived from experience. This becomes part of his over-all argument for transcendental idealism. That is, he argues that the possibility of experience depends on certain necessary conditions—which he calls a priori forms—and that these conditions structure and hold true of the world of experience. In so doing, his main claims in the "Transcendental Aesthetic" are that mathematic judgments are synthetic a priori and in addition, that Space and Time are not derived from experience but rather are its preconditions.
Once we have grasped the concepts of addition, subtraction or the functions of basic arithmetic, we do not need any empirical experience to know that 100 + 100 = 200, and in this way it would appear that arithmetic is in fact analytic. However, that it is analytic can be disproved thus: if the numbers five and seven in the calculation 5 + 7 = 12 are examined, there is nothing to be found in them by which the number 12 can be inferred. Such it is that "5 + 7" and "the cube root of 1,728" or "12" are not analytic because their reference is the same but their sense is not—that the mathematic judgment "5 + 7 = 12" tells us something new about the world. It is self-evident, and undeniably a priori, but at the same time it is synthetic. And so Kant proves a proposition can be synthetic and known a priori.
Kant asserts that experience is based both upon the perception of external objects and a priori knowledge. The external world, he writes, provides those things which we sense. It is our mind, though, that processes this information about the world and gives it order, allowing us to comprehend it. Our mind supplies the conditions of space and time to experienced objects. According to the "transcendental unity of apperception", the concepts of the mind (Understanding) and the perceptions or intuitions that garner information from phenomena (Sensibility) are synthesized by comprehension. Without the concepts, intuitions are nondescript; without the intuitions, concepts are meaningless—thus the famous quotation, "Thoughts without content are empty, intuitions without concepts are blind.
In studying the work of Kant one must realize that there is a distinction between "understanding" as the general concept (in German, das Verstehen) and the "understanding" as a faculty of the human mind (in German, der Verstand). In much English language scholarship, the word "understanding" is used in both senses.
Immanuel Kant deemed it obvious that we have some objective knowledge of the world, such as, say, Newtonian physics. But this knowledge relies on synthetic, a priori laws of nature, like causality and substance. The problem, then, is how this is possible. Kant’s solution was to reason that the subject must supply laws that make experience of objects possible, and that these laws are the synthetic, a priori laws of nature which we can know all objects are subject to prior to experiencing them. So to deduce all these laws, Kant examined experience in general, dissecting in it what is supplied by the mind from what is supplied by the given intuitions. This which has just been explicated is commonly called a transcendental reduction.
To begin with, Kant’s distinction between the a posteriori being contingent and particular knowledge, and the a priori being universal and necessary knowledge, must be kept in mind. For if we merely connect two intuitions together in a perceiving subject, the knowledge will always be subjective because it is derived a posteriori, when what is desired is for the knowledge to be objective, that is, for the two intuitions to refer to the object and hold good of it necessarily universally for anyone at anytime, not just the perceiving subject in its current condition. Now what else is equivalent to objective knowledge besides the a priori, that is to say, universal and necessary knowledge? Nothing else, and hence before knowledge can be objective, it must be incorporated under an a priori category of the understanding.
For example, say a subject says, “The sun shines on the stone; the stone grows warm”, which is all he perceives in perception. His judgment is contingent and holds no necessity. But if he says, “The sunshine causes the stone to warm”, he subsumes the perception under the category of causality, which is not found in the perception, and necessarily synthesizes the concept sunshine with the concept heat, producing a necessarily universally true judgment.
To explain the categories in more detail, they are the preconditions of the construction of objects in the mind. Indeed, to even think of the sun and stone presupposes the category of subsistence, that is, substance. For the categories synthesize the random data of the sensory manifold into intelligible objects. This means that the categories are also the most abstract things one can say of any object whatsoever, and hence one can have an a priori cognition of the totality of all objects of experience if one can list all of them. To do so, Kant formulates another transcendental reduction.
Judgments are, for Kant, the preconditions of any thought. Man thinks via judgments, so all possible judgments must be listed and the perceptions connected within them put aside, so as to make it possible to examine the moments when the understanding is engaged in constructing judgments. For the categories are equivalent to these moments, in that they are concepts of intuitions in general, so far as they are determined by these moments universally and necessarily. Thus by listing all the moments, one can deduce from them all of the categories.
One may now ask: How many possible judgments are there? Kant believed that all the possible propositions within Aristotle’s syllogistic logic are equivalent to all possible judgments, and that all the logical operators within the propositions are equivalent to the moments of the understanding within judgments. Thus he listed Aristotle’s system in four groups of three: quantity (universal, particular, singular), quality (affirmative, negative, infinite), relation (categorical, hypothetical, disjunctive) and modality (problematic, assertoric, apodeictic). The parallelism with Kant’s categories is obvious: quantity (unity, plurality, totality), quality (reality, negation, limitation), relation (substance, cause, community) and modality (possibility, existence, necessity).
The fundamental building blocks of experience, i.e. objective knowledge, are now in place. First there is the sensibility, which supplies the mind with intuitions, and then there is the understanding, which produces judgments of these intuitions and can subsume them under categories. These categories lift the intuitions up out of the subject’s current state of consciousness and place them within consciousness in general, producing universally necessary knowledge. For the categories are innate in any rational being, so any intuition thought within a category in one mind will necessarily be subsumed and understood identically in any mind.
Kant ran into a problem with his theory that the mind plays a part in producing objective knowledge. Intuitions and categories are entirely disparate, so how can they interact? Kant’s solution is the schema: a priori principles by which the transcendental imagination connects concepts with intuitions through time. All the principles are temporally bound, for if a concept is purely a priori, as the categories are, then they must apply for all times. Hence there are principles such as substance is that which endures through time, and the cause must always be prior to the effect.
In the Groundwork, Kant's method involves trying to convert our everyday, obvious, rational knowledge of morality into philosophical knowledge. The latter two works followed a method of using "practical reason", which is based only upon things about which reason can tell us, and not deriving any principles from experience, to reach conclusions which are able to be applied to the world of experience (in the second part of The Metaphysic of Morals).
Kant is known for his theory that there is a single moral obligation, which he called the "Categorical Imperative", and is derived from the concept of duty. Kant defines the demands of the moral law as "categorical imperatives." Categorical imperatives are principles that are intrinsically valid; they are good in and of themselves; they must be obeyed in all situations and circumstances if our behavior is to observe the moral law. It is from the Categorical Imperative that all other moral obligations are generated, and by which all moral obligations can be tested. Kant also stated that the moral means and ends can be applied to the categorical imperative, that rational beings can pursue certain "ends" using the appropriate "means." Ends that are based on physical needs or wants will always give for merely hypothetical imperatives. The categorical imperative, however, may be based only on something that is an "end in itself". That is, an end that is a means only to itself and not to some other need, desire, or purpose. He believed that the moral law is a principle of reason itself, and is not based on contingent facts about the world, such as what would make us happy, but to act upon the moral law which has no other motive than "worthiness of being happy". Accordingly, he believed that moral obligation applies to all and only rational agents.
A categorical imperative is an unconditional obligation; that is, it has the force of an obligation regardless of our will or desires (Contrast this with hypothetical imperative) In Groundwork of the Metaphysic of Morals (1785) Kant enumerated three formulations of the categorical imperative which he believed to be roughly equivalent:
Kant believed that if an action is not done with the motive of duty, then it is without moral value. He thought that every action should have pure intention behind it; otherwise it was meaningless. He didn't necessarily believe that the final result was the most important aspect of an action, but that how the person felt while carrying out the action was the time at which value was set to the result.
In Groundwork of the Metaphysic of Morals, Kant also posited the "counter-utilitarian idea that there is a difference between preferences and values and that considerations of individual rights temper calculations of aggregate utility", a concept that is an axiom in economics:
Everything has either a price or a dignity. Whatever has a price can be replaced by something else as its equivalent; on the other hand, whatever is above all price, and therefore admits of no equivalent, has a dignity. But that which constitutes the condition under which alone something can be an end in itself does not have mere relative worth, i.e., price, but an intrinsic worth, i.e., a dignity. (p. 53, italics in original).
A phrase quoted by Kant, which is used to summarize the counter-utilitarian nature of his moral philosophy, is Fiat justitia, pereat mundus, ("Let justice be done, though the world perish"), which he translates loosely as "Let justice reign even if all the rascals in the world should perish from it". This appears in his 1795 Perpetual Peace (Zum ewigen Frieden), Appendix 1.
One interpretation of the first formulation is called the "universalisability test". An agent's maxim, according to Kant, is his "subjective principle of human actions": that is, what the agent believes is his reason to act. The universalisability test has five steps:
Kant calls practical "everything that is possible through freedom", and the pure practical laws that are never given through sensuous conditions but are held analogously with the universal law of causality are moral laws. Reason can give us only the "pragmatic laws of free action through the senses", but pure practical laws given by reason a priori dictate "what ought to be done".
In the chapter "Analytic of the Beautiful" of the Critique of Judgment, Kant states that beauty is not a property of an artwork or natural phenomenon, but is instead a consciousness of the pleasure which attends the 'free play' of the imagination and the understanding. Even though it appears that we are using reason to decide that which is beautiful, the judgment is not a cognitive judgment, "and is consequently not logical, but aesthetical" (§ 1). A pure judgement of taste is in fact subjective insofar as it refers to the emotional response of the subject and is based upon nothing but esteem for an object itself: it is a disinterested pleasure, and we feel that pure judgements of taste, i.e. judgements of beauty, lay claim to universal validity (§§20–22). It is important to note that this universal validity is not derived from a determinate concept of beauty but from common sense. Kant also believed that a judgement of taste shares characteristics engaged in a moral judgement: both are disinterested, and we hold them to be universal. In the chapter "Analytic of the Sublime" Kant identifies the sublime as an aesthetic quality which, like beauty, is subjective, but unlike beauty refers to an indeterminate relationship between the faculties of the imagination and of reason, and shares the character of moral judgments in the use of reason. The feeling of the sublime, itself comprised of two distinct modes (the mathematical sublime and the dynamical sublime), describe two subjective moments both of which concern the relationship of the faculty of the imagination to reason. The mathematical sublime is situated in the failure of the imagination to comprehend natural objects which appear boundless and formless, or which appear "absolutely great" (§ 23–25). This imaginative failure is then recuperated through the pleasure taken in reason's assertion of the concept of infinity. In this move the faculty of reason proves itself superior to our fallible sensible self (§§ 25–26). In the dynamical sublime there is the sense of annihilation of the sensible self as the imagination tries to comprehend a vast might. This power of nature threatens us but through the resistance of reason to such sensible annihilation, the subject feels a pleasure and a sense of the human moral vocation. This appreciation of moral feeling through exposure to the sublime helps to develop moral character.
Kant had developed the distinction between an object of art as a material value subject to the conventions of society and the transcendental condition of the judgment of taste as a "refined" value in the propositions of his Idea of A Universal History (1784). In the Fourth and Fifth Theses of that work he identified all art as the "fruits of unsociableness" due to men's "antagonism in society", and in the Seventh Thesis asserted that while such material property is indicative of a civilized state, only the ideal of morality and the universalization of refined value through the improvement of the mind of man "belongs to culture".
He opposed "democracy," which at his time meant direct democracy, believing that majority rule posed a threat to individual liberty. He stated, "…democracy is, properly speaking, necessarily a despotism, because it establishes an executive power in which 'all' decide for or even against one who does not agree; that is, 'all,' who are not quite all, decide, and this is a contradiction of the general will with itself and with freedom.
The vastness of Kant's influence on Western thought is immeasurable. Over and above his specific influence on specific thinkers, Kant changed the framework within which philosophical inquiry has been carried out from his day through the present in ways that have been irreversible. In other words, he accomplished a paradigm shift: very little philosophy since Kant has been carried out as an extension of pre-Kantian philosophy or in the mode of thought and discourse of pre-Kantian philosophy. This shift consists in several closely related innovations that have become axiomatic to post-Kantian thought, both in philosophy itself and in the social sciences and humanities generally:
Some or all of these Kantian ideas can be seen in schools of thought as different from one another as German Idealism, Marxism, positivism, phenomenology, existentialism, critical theory, linguistic philosophy, structuralism, post-structuralism, and deconstructionism. Kant's influence also has extended to the social and behavioral sciences, as in the sociology of Max Weber, the psychology of Jean Piaget, and the linguistics of Noam Chomsky. Because of the thoroughness of the Kantian paradigm shift, his influence extends even to thinkers who do not specifically refer to his work or use his terminology.
During his own life, there was a considerable amount of attention paid to his thought, much of it critical, though he did have a positive influence on Reinhold, Fichte, Schelling, Hegel, and Novalis during the 1780s and 1790s. The philosophical movement known as German Idealism developed from Kant's theoretical and practical writings. The German Idealists Fichte and Schelling, for example, attempted to bring traditionally "metaphysically" laden notions like "the Absolute," "God," or "Being" into the scope of Kant's critical philosophy. In so doing, the German Idealists attempted to reverse Kant's establishment of the unknowableness of unexperiencable ideas.
Hegel was one of the first major critics of Kant's philosophy. Hegel thought Kant's moral philosophy was too formal, abstract and ahistorical. In response to Kant's abstract and formal account of morality, Hegel developed an ethics that considered the "ethical life" of the community. But Hegel's notion of "ethical life" is meant to subsume, rather than replace, Kantian "morality." And Hegel's philosophical work as a whole can be understood as attempting to defend Kant's conception of freedom as going beyond finite "inclinations," by means of reason. Thus, in contrast to later critics like Friedrich Nietzsche or Bertrand Russell, Hegel shares some of Kant's most basic concerns.
Many British Roman Catholic writers, notably G. K. Chesterton and Hilaire Belloc, seized on Kant and promoted his work, with a view to restoring the philosophical legitimacy of a belief in God. Reaction against this, and an attack on Kant's use of language, is found in Ronald Englefield's article, "Kant as Defender of the Faith in Nineteenth-century England, reprinted in Critique of Pure Verbiage, Essays on Abuses of Language in Literary, Religious, and Philosophical Writings.
Arthur Schopenhauer was strongly influenced by Kant's transcendental idealism. He, like G. E. Schulze, Jacobi and Fichte before him, was critical of Kant's theory of the thing in itself. Things in themselves, they argued, are neither the cause of our representations nor are they something completely beyond our access. For Schopenhauer things in themselves do not exist independently of the non-rational will. The world, as Schopenhauer would have it, is the striving and largely unconscious will.
With the success and wide influence of Hegel's writings, Kant's influence began to wane, though there was in Germany a brief movement that hailed a return to Kant in the 1860s, beginning with the publication of Kant und die Epigonen in 1865 by Otto Liebmann, whose motto was "Back to Kant". During the turn of the 20th century there was an important revival of Kant's theoretical philosophy, known as Marburg Neo-Kantianism, represented in the work of Hermann Cohen, Paul Natorp, Ernst Cassirer, and anti-Neo-Kantian Nicolai Hartmann.
Jurgen Habermas and John Rawls are two significant political and moral philosophers whose work is strongly influenced by Kant's moral philosophy. They both, regardless of recent relativist trends in philosophy, have argued that universality is essential to any viable moral philosophy.
Kant's notion of "Critique" or criticism has been quite influential. The Early German Romantics, especially Friedrich Schlegel in his "Athenaeum Fragments", used Kant's self-reflexive conception of criticism in their Romantic theory of poetry. Also in Aesthetics, Clement Greenberg, in his classic essay "Modernist Painting", uses Kantian criticism, what Greenberg refers to as "immanent criticism", to justify the aims of Abstract painting, a movement Greenberg saw as aware of the key limitiaton—flatness—that makes up the medium of painting.
Kant believed that mathematical truths were forms of synthetic a priori knowledge, which means they are necessary and universal, yet known through intuition. Kant’s often brief remarks about mathematics influenced the mathematical school known as intuitionism, a movement in philosophy of mathematics opposed to Hilbert’s formalism, and the logicism of Frege and Bertrand Russell. Post-Kantian philosophy has yet to return to the style of thinking and arguing that characterized much of philosophy and metaphysics before Kant, although many British and American philosophers have preferred to trace their intellectual origins to Hume, thus bypassing Kant. The British philosopher P. F. Strawson is a notable exception, as is the American philosopher Wilfrid Sellars.
Due in part to the influence of Strawson and Sellars, among others, there has been a renewed interest in Kant's view of the mind. Central to many debates in philosophy of psychology and cognitive science is Kant's conception of the unity of consciousness.
Kant's tomb is today in a mausoleum adjoining the northeast corner of Königsberg Cathedral. The mausoleum was constructed by the architect Friedrich Lahrs and was finished in 1924 in time for the bicentenary of Kant's birth. Originally, Kant was buried inside the cathedral, but in 1880 his remains were moved outside and placed in a neo-Gothic chapel adjoining the northeast corner of the cathedral. Over the years, the chapel became dilapidated before it was demolished to make way for the mausoleum, which was built on the same spot, where it is today.
The tomb and its mausoleum are some of the few artefacts of German times preserved by the Soviets after they conquered and annexed the city. Today, many newlyweds bring flowers to the mausoleum.
A replica of the statue of Kant that stood in German times in front of the main University of Königsberg building was donated by a German entity in the early 1990s and placed in the same grounds.