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Immanuel Kant

Related subjects Philosophers

Immanuel Kant
Western Philosophy
18th-century philosophy

Immanuel Kant
Full name Immanuel Kant
Birth April 22, 1724
Königsberg, Kingdom of Prussia
Death February 12, 1804 (aged 79)
Königsberg, Kingdom of Prussia
School/tradition Kantianism, enlightenment philosophy
Main interests Epistemology, Metaphysics, Ethics
Notable ideas Categorical imperative, Transcendental Idealism, Synthetic a priori, Noumenon, Sapere aude, Nebular hypothesis

Immanuel Kant IPA [ɪmanuəl 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.

Among his most important works are the Critique of Pure Reason and the Critique of Practical Reason, which examine the relation of epistemology, metaphysics, and ethics.


Immanuel Kant was born in 1724 in Königsberg, as the fourth of eleven children (five of them reached adulthood). He was baptized as 'Emanuel' but later changed his name to 'Immanuel' after he learned Hebrew. He spent his entire life in and around his hometown, the capital of Prussia at that time, never traveling more than a hundred miles from Königsberg. His father Johann Georg Kant (1682–1746) was a German craftsman from Memel, at the time Prussia's most northeastern city (now Klaipėda, Lithuania). His mother Anna Regina Porter (1697–1737), born in Nuremberg, was the daughter of a Scottish saddle and harness maker. In his youth, Kant was a solid, albeit unspectacular, student. He was raised in a Pietist household that stressed intense religious devotion, personal humility, and a literal interpretation of the Bible. Consequently, Kant received a stern education — strict, punitive, and disciplinary — that favored Latin and religious instruction over mathematics and science.

The Young Scholar

Kant showed great application to study early in his life. He was first sent to Collegium Fredericianum and then enrolled in the University of Königsberg in 1740, at the age of 16. He studied the philosophy of Leibniz and Wolff under Martin Knutsen, a rationalist who was also familiar with developments in British philosophy and science and who introduced Kant to the new mathematical physics of Newton. Knutsen dissuaded Kant from the theory of pre-established harmony, which he regarded as "the pillow for the lazy mind". He also dissuaded the young scholar from idealism, which was negatively regarded by the whole philosophy of the 18th century. Even after Kant developed the theory of transcendental idealism in the "Critique of Pure Reason", he nevertheless refuted traditional idealism, i.e. the idea that reality is mental, in the second part of that work. His father's stroke and subsequent death in 1746 interrupted his studies. Kant became a private tutor in the smaller towns surrounding Königsberg, but continued his scholarly research. 1749 saw the publication of his first philosophical work, Thoughts on the True Estimation of Living Forces. Kant published several more works on scientific topics, becoming a university lecturer in 1755. The subject on which he lectured was "Metaphysics"; the course textbook was written by A.G. Baumgarten, the author of the term "aesthetics" in its modern meaning.

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 (colour, 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 (actually a dense cable of individual nerve cells) 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 itself not fully grounded. But the uncertainty aroused by this considerations, the uncertainties raised by optical illusions, misperceptions, delusions, etc., are not the end of the worries of the philosopher who is no longer slumbering. Donald Davidson, an influential Stanford University professor of philosophy, introduced the next level of perplexity by pointing out that simply having a mapping, something like a little television screen somewhere in the brain, does not at all answer the question of how humans then think about or process the information present in that form. Imagine, Davidson said, that there is a little man in the brain who watches the television screen and directs the whole organism based on those perceptions. But, wait, that will not work either because the little man has his own eyes, and a mapping of the image on the television screen appears on an even tinier television screen in his brain. And immediately upon discovering this chain of dependence it becomes clear that it implies infinite regress.

So something else has to be going on. There may indeed be a mapping in the brain. In fact, brain scientists can actually find physical maps of the body in the brain. The volume of cells that monitors the hand has the approximate form of a human hand, for instance. But somehow the mind, or the brain, has to "reach out" and comprehend that mapping and in some way process the information in a way that does not simply create another mapping of it.

Without knowing the details now known about neurophysiology, Kant clearly saw that the mind could not function if it were only an empty container at the end of a fire hose of data coming in from the outside. Something had to be giving order to the incoming data. If, for instance, part of the incoming data included a visual mapping of a fertile frog egg, then that data would not remain constant. It would be followed by visual mappings of the tadpole and frog sorts. But, to be useful information for the budding biology student, some kind of meta-data would have to be created to keep those images in the same sequence in which they were received. The ordering of data in this kind of sequence is the mind's function of constituting time for the purposes of human awareness of the environment. The same general 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.

As Willard van Orman Quine pointed out much later in his Logic, the internal storage of visual data does not even have to be stored in contiguous portions of the brain, any more than a computer file on a hard drive has to be entirely in one solid block on a hard drive. As long as the brain has a mapping of where it has put the parts of the visual record of the tadpole or the frog, those parts can "written" anywhere. Or, to put it in terms more closely approximating Quine's original formulation, an entity does not have to be contiguous to be an entity.

The Silent Decade

At the age of 46, Kant was an established scholar and an increasingly influential philosopher. Much was expected of him. In response to a letter from his student, Markus Herz, Kant came to recognize that in the Inaugural Dissertation, he had failed to account for the relation and connection between our sensible and intellectual faculties, i.e., he needed to explain both how humans acquire data and how they process data—related but very different processes. He also credited David Hume with awakening him from "dogmatic slumber" (circa 1770). Kant did not publish any work in philosophy for the next eleven years.

Immanuel Kant
Immanuel Kant

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's later work

Kant published a second edition of the Critique of Pure Reason (Kritik der reinen Vernunft) in 1787, heavily revising the first parts of the book. Most of his subsequent work focused on other areas of philosophy. He continued to develop his moral philosophy, notably in 1788's Critique of Practical Reason (known as the second Critique) and 1797’s Metaphysics of Morals. The 1790 Critique of Judgment (the third Critique) applied the Kantian system to aesthetics and teleology. He also wrote a number of semi-popular essays on history, religion, politics and other topics. These works were well received by Kant's contemporaries and confirmed his preeminent status in eighteenth century philosophy. There were several journals devoted solely to defending and criticizing the Kantian philosophy. But despite his success, philosophical trends were moving in another direction. Many of Kant's most important disciples (including Reinhold, Beck and Fichte) transformed the Kantian position into increasingly radical forms of idealism. The progressive stages of revision of Kant's teachings marked the emergence of German Idealism. Kant opposed these developments and publicly denounced Fichte in an open letter in 1799. It was one of his final philosophical acts. Kant's health, long poor, took a turn for the worse and he died at Konigsberg on 12 February 1804 uttering "Genug" [enough] before expiring. His unfinished final work, the fragmentary Opus Postumum, was (as its title suggests) published posthumously.

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.

Kant the man

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. Only later in his life, under the influence of his friend, the English merchant Joseph Green, did Kant adopt a more regulated lifestyle.

Kant's philosophy

In his essay " Answering the Question: What is Enlightenment?," Kant defined the Enlightenment as an age shaped by the Latin motto, Sapere aude ("Dare to Know"). Kant maintained that one ought to think autonomously, free of the dictates of external authority. His work reconciled many of the differences between the Rationalist and Empiricist traditions of the 18th century. He had a decisive impact on the Romantic and German Idealist philosophies of the 19th century. His work has also been a starting point for many 20th century philosophers.

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:

All the preparations of reason, therefore, in what may be called pure philosophy, are in reality directed to those three problems only [God, the soul, and freedom]. However, these three elements in themselves still hold independent, proportional, objective weight individually. Moreover, in a collective relational context; namely, to know what ought to be done: if the will is free, if there is a God, and if there is a future world. As this concerns our actions with reference to the highest aims of life, we see that the ultimate intention of nature in her wise provision was really, in the constitution of our reason, directed to moral interests only.

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 centre 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's theory of perception

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.

  1. Analytic proposition: a proposition whose predicate concept is contained in its subject concept; e.g., "All bachelors are unmarried," or, "All bodies take up space."
  2. Synthetic proposition: a proposition whose predicate concept is not contained in its subject concept ; e.g., "All bachelors are happy," or, "All bodies have mass."

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

This is quite naturally confusing, yet Kant's idea is that since his first claim—about mathematic judgments—is true, then it will follow that his claims about space and time are true as well. The next paragraph deals with the notion of mathematic judgments being synthetic a priori, skip to the paragraph afterward to read more about perception and Kant.

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."

Kant’s Categories of the Faculty of Understanding

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’s Schema

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.

Moral philosophy

Immanuel Kant
Immanuel Kant

Kant developed his moral philosophy in three works: Groundwork of the Metaphysic of Morals (1785), Critique of Practical Reason (1788), and Metaphysics of Morals (1797) .

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 behaviour 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).

The first formulation

The first formulation (Formula of Universal Law) of the moral imperative "requires that the maxims be chosen as though they should hold as universal laws of nature" (436). This formulation in principle has as its supreme law "Always act according to that maxim whose universality as a law you can at the same time will", and is the "only condition under which a will can never come into conflict with itself…"

One interpretation of the first formulation is called the "universalizability 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 universalizability test has five steps:

  1. Find the agent's maxim. The maxim is an action paired with its motivation. Example: "I will lie for personal benefit." Lying is the action, the motivation is to get what you desire. Paired together they form the maxim.
  2. Imagine a possible world in which everyone in a similar position to the real-world agent followed that maxim.
  3. Decide whether any contradictions or irrationalities arise in the possible world as a result of following the maxim.
  4. If a contradiction or irrationality arises, acting on that maxim is not allowed in the real world.
  5. If there is no contradiction, then acting on that maxim is permissible, and in some instances required.

(For a modern parallel, see John Rawls' hypothetical situation, the original position.)

The second formulation

The second formulation (Formula of the End in Itself) says that "the rational being, as by its nature an end and thus as an end in itself, must serve in every maxim as the condition restricting all merely relative and arbitrary ends." The principle is "Act with reference to every rational being (whether yourself or another) so that it is an end in itself in your maxim…", meaning the rational being is "the basis of all maxims of action" and "must be treated never as a mere means but as the supreme limiting condition in the use of all means, i.e., as an end at the same time."

The third formulation

The third formulation (Formula of Autonomy) is a synthesis of the first two and is the basis for the "complete determination of all maxims". It says "that all maxims which stem from autonomous legislation ought to harmonize with a possible realm of ends as with a realm of nature." In principle, "So act as if your maxims should serve at the same time as the universal law (of all rational beings)", meaning that we should so act that we may think of ourselves as "a member in the universal realm of ends", legislating universal laws through our maxims, in a "possible realm of ends." (See also Kingdom of Ends)

Idea of God

Kant stated the practical necessity for a belief in God in his Critique of Pure Reason. As an idea of pure reason, "we do not have the slightest ground to assume in an absolute manner… the object of this idea…", but adds that the idea of God cannot be separated from the relation of happiness with morality as the "ideal of the supreme good." The foundation of this connection is an intelligible moral world, and "is necessary from the practical point of view". Later, in the Logic, § 3 (1800) he argued that the idea of God can only be proved through the moral law and only with practical intent, that is, "the intent so as to act as if there be a God" (trans. Hartmann and Schwartz). See Argument from morality for more details.

Idea of freedom

In the Critique of Pure Reason Kant distinguishes between the transcendental idea of freedom, which as a psychological concept is "mainly empirical" and refers to "the question whether we must admit a power of spontaneously beginning a series of successive things or states" as a real ground of necessity in regard to causality, and the practical concept of freedom as the independence of our will from the "coercion" or "necessitation through sensuous impulses." Kant finds it a source of difficulty that the practical concept of freedom is founded on the transcendental idea of freedom, but for the sake of practical interests uses the practical meaning, taking "no account of… its transcendental meaning", which he feels was properly "disposed of" in the Third Antinomy, and as an element in the question of the freedom of the will is for philosophy "a real stumbling-block" that has "embarrassed speculative reason".

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".

Aesthetic philosophy

Kant discusses the subjective nature of aesthetic qualities and experiences in Observations on the Feeling of the Beautiful and Sublime, (1764). Kant's contribution to aesthetic theory is developed in the Critique of Judgment (1790) where he investigates the possibility and logical status of "judgments of taste." In the "Critique of Aesthetic Judgment," the first major division of the Critique of Judgment, Kant used the term "aesthetic" in a manner that is, according to Kant scholar W.H. Walsh, its modern sense. Prior to this, in the Critique of Pure Reason, Kant had, in order to note the essential differences between judgments of taste, moral judgments, and scientific judgments, abandoned the use of the term "aesthetic" as "designating the critique of taste," noting that judgments of taste could never be "directed" by "laws a priori". After A. G. Baumgarten, who wrote Aesthetica (1750–58), Kant was one of the first philosophers to develop and integrate aesthetic theory into a unified and comprehensive philosophical system, utilizing ideas that played an integral role throughout his philosophy.

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".

Political philosophy

In Perpetual Peace: A Philosophical Sketch (1795) Kant listed several conditions that he thought necessary for ending wars and creating a lasting peace. They included a world of constitutional republics. This was the first version of the democratic peace theory.

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."


Kant lectured on anthropology for over 25 years. His Anthropology from a Pragmatic Point of View was published in 1798. (This was the subject of Michel Foucault's doctoral dissertation.) Kant's Lectures on Anthropology was published for the first time in 1997 in German. They have not been translated into English.


Statue of Immanuel Kant in Kaliningrad, Russia
Statue of Immanuel Kant in Kaliningrad, Russia

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:

  • Kant's "Copernican revolution", that placed the role of the human subject or knower at the centre of inquiry into our knowledge, such that it is impossible to philosophize about things as they are independently of us or of how they are for us;
  • his invention of critical philosophy, that is of the notion of being able to discover and systematically explore possible inherent limits to our ability to know through philosophical reasoning;
  • his creation of the concept of "conditions of possibility", as in his notion of "the conditions of possible experience" -- that is that things, knowledge, and forms of consciousness rest on prior conditions that make them possible, so that to understand or know them we have to first understand these conditions;
  • his theory that objective experience is actively constituted or constructed by the functioning of the human mind;
  • his notion of moral autonomy as central to humanity;
  • his assertion of the principle that human beings should be treated as ends rather than as means.

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 behavioural 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.

West German postage stamp, 1974, commemorating the 250th anniversary of Kant's birth.
West German postage stamp, 1974, commemorating the 250th anniversary of Kant's birth.

With his Perpetual Peace, Kant is considered to have foreshadowed many of the ideas that have come to form the democratic peace theory, one of the main controversies in political science.

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.

Tomb & Statue in Kaliningrad

Immanuel Kant's tomb today
Immanuel Kant's tomb today
Plaque on a wall in Kaliningrad, in German and Russian, with the words taken from the conclusion of Kant's Critique of Practical Reason: Two things fill the mind with ever new and increasing admiration and awe, the more often and steadily we reflect upon them: the starry heavens above me and the moral law within me. (The wall is next to where the southwest part of Königsberg Castle used to be.)
Plaque on a wall in Kaliningrad, in German and Russian, with the words taken from the conclusion of Kant's Critique of Practical Reason: Two things fill the mind with ever new and increasing admiration and awe, the more often and steadily we reflect upon them: the starry heavens above me and the moral law within me. (The wall is next to where the southwest part of Königsberg Castle used to be.)

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.

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