Immanuel Kant

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A painting of Immanuel Kant in his middle age
A painting of Immanuel Kant in his middle age

Immanuel Kant (April 22, 1724 in KnigsbergFebruary 12, 1804) was a German philosopher from Prussia, generally regarded as one of Europe's most influential thinkers and the last major philosopher of the Enlightenment. He had a major impact on the Romantic and Idealist philosophies of the 19th century, and his work was the starting point for Hegel.

The key doctrine of Kant's philosophy, called transcendental idealism, is that the mind knows objects in the world only by means of sensible forms, space and time, which it produces itself. Without these forms, Kant argues, knowledge would not be possible because the mind would have no way to order or structure the data given to it by the senses. Kant therefore claims that we know objects only as they "appear" in space and time (rather than as "things in themselves"). While the specifics of Kant's account generated immediate and lasting controversy, his thesis that the mind itself makes a constitutive contribution to its knowledge (and that knowledge is therefore subject to limits which cannot be overcome) nevertheless irrevocably reshaped philosophy. Similarly, his argument that human beings are free inasmuch as their power of reason itself dictates a moral law for their actions redefined the terms of philosophical debate about morality.



Kant was born, lived and died in Knigsberg, the capital of East Prussia, a city which today is Kaliningrad in the Russian exclave of that name. His parents baptized him as Emanuel Kant, which he later, after learning Hebrew, changed to Immanuel. He spent much of his youth as a solid, albeit unspectacular, student. Contrary to the dour image of him promoted by early biographers, Kant as a young man was quite gregarious and enjoyed attending social events about town. He also regularly invited guests over for dinner, insisting that company and laughter were good for his constitution. It was only after befriending the English merchant Joseph Green, who instilled in Kant a respect for living according to strictly observed maxims of behavior, that Kant began living a very regulated life: according to some stories neighbors would set their clocks according to the time Green and Kant finished their daily get-togethers. A biography of Kant by Manfred Kuehn even suggests that Kant was philosophically inspired by Green, who not only introduced him to the philosophy of David Hume, but whose personal habits may have influenced Kant in formulating his idea of the categorical imperative. [1] ( Another influential view about the introduction of the works of Hume to Kant and other German philosophers, which finds its clearest expression in the works of Frederick C. Beiser, is that it was Johann Georg Hamann (1730-1788) who brought Hume's views to Germany. For the remainder of his life Kant remained unmarried and owned only one piece of art in his household, advocating the absence of passion in favor of logic. He never left Prussia and rarely stepped outside his own home town. He was a respected and competent university professor for most of his life, although he was in his late fifties before he did anything that would bring him historical repute.

He entered the local university in 1740, and studied the philosophy of Leibniz and Christian Wolff under Martin Knutsen, a follower of Wolff. He also studied the new mathematics of Sir Isaac Newton and, in 1746, wrote a paper on measurement, reflecting Leibniz's influence. In 1755, he became a private lecturer at the University, and while there published "Inquiry into the Distinctness of the Principles of Natural Theology and Morals", where he examined the problem of having a logical system of philosophy that connected with the world of natural philosophy, a concern typical of the period. In this paper, he proposed what later become known as the Kant-Laplace theory of planetary formation, wherein the planets formed from rotating protoplanetary disks of gas. Kant was also the first recorded scholar to postulate (as is true) that some of the faint nebulae one can see with a small telescope (or in one case, with the naked eye) were external galaxies or, as he called them, island universes. Kant's prescient remarks on island universes. (

In 1763, he wrote The Only Possible Ground of Proof for a Demonstration of God's Existence, which questioned the ontological argument for God put forward by Saint Anselm of Canterbury in the 11th century, namely that the greatest of all possible ideas must include the attribute of existence, because if it does not, it is not the greatest of all possible ideas. Therefore, God, who by definition is the greatest of all possible ideas, must exist. Rene Descartes put forward a similar argument in the Fifth Meditation. Despite questioning this argument however, Kant in this piece defends a modified form of rational theology, which he subsequently rejected in his Critical work.

In 1766, he was appointed Second Librarian of the Royal Library, a prestigious government position. In 1770, he became a full professor at Knigsberg. It was after this time that Hume's works began to have serious impact on his understanding of metaphysics though there is considerable evidence he had read Hume earlier and that it was only the breakdown of an early attempt at constructing a rationalist metaphysics that led him to see Hume's contribution to philosophy as decisive. Hume was fiercely empirical, scorned all metaphysics, and systematically debunked great quantities of it. His most famous thesis is that nothing in our experience can justify the assumption that there are "causal powers" inherent in things — that, for example, when one billiard ball strikes another, the second must move. Kant found Hume's conclusions unacceptable. "I wilfully admit that it was David Hume that woke me from my dogmatic slumber", he would later write.

For the next 10 years, he worked on the architecture of his own philosophy. In 1781, he released the Critique of Pure Reason, one of the most influential, widely cited, and widely disputed works in Western philosophy. He followed this with Groundwork of the Metaphysics of Morals, then in 1788, the Critique of Practical Reason and in 1790, the Critique of Judgement. The effect was immediate in the German-speaking world, with readership including Ludwig van Beethoven and Johann Wolfgang von Goethe. But the attention was far from universally approving: on the contrary, almost every aspect of his writing was attacked and criticized fiercely, particularly his ideas on categories, the place of free will and determinism, and whether we can have knowledge of external reality. His early critics included Johann Schaumann, Friedrich Heinrich Jacobi and Hermann Pistorius. Pistorius' criticisms were particularly influential and are still cited today.

The inscription near Kant's tomb in ,
The inscription near Kant's tomb in Kaliningrad, Russia

The Critique of Practical Reason dealt with morality, or action, in the same way that the first Critique dealt with knowledge, and the Critique of Judgement dealt with the various uses of our mental powers that neither confer factual knowledge nor determine us to action, such as aesthetic judgement, for example of the beautiful and sublime, and teleological judgment, that is, construing things as having "purposes". As Kant understood them, aesthetic and teleological judgment connected our moral and empirical judgments to one another, unifying his system. Two shorter works, the Prolegomena to any Future Metaphysics and the Groundwork to the Metaphysics of Morals treated the same matter as the first and second critiques respectively, in a more cursory form — assuming the answer and working backward, so to speak. They serve as his introductions to the critical system.

The epistemological material of the first Critique was put into application in the Metaphysical Foundations of Natural Science; the ethical dictums of the second were put into practice in Metaphysics of Morals. His work on moral philosophy is best known for its formulation of a basic tenet of ethics, sometimes falsely assumed to be an extension of the Golden Rule, which Kant called the categorical imperative: "Act only on that maxim whereby thou canst at the same time will that it should become a universal law."

Kant also wrote a number of semi-popular essays on history, politics, and the application of philosophy to life. When he died in 1804, he was working on an incomplete manuscript that has been published as Opus Postumum.

His tomb and its pillared enclosure outside the cathedral in Knigsberg is one of the few artifacts of German times preserved by the Soviets after they conquered East Prussia in 1945. A replica of a statue of Kant that stood in front of the university was donated by a German entity in 1991 and placed on the original pediment. The inscription near his tomb, in German and Russian, reads:

Two things fill the mind with ever new and increasing admiration and awe, the more often and perseveringly my thinking engages itself with them: the starry heavens above me and the moral law within me.

The Critique of Pure Reason

Kant's most widely read and most influential book is Critique of Pure Reason [2] ( (1781) - his attempt to work past what he saw as the unacceptable conclusions of David Hume. Kant wanted to find the limitations of Reason, and its application to such important philosophical questions as whether there is a God, the immortality of the soul, and freedom.

Hume's conclusions, Kant realized, rested on the premise that knowledge is empirical at its root. The problem that Hume identified was that basic principles like cause and effect cannot be empirically derived. Kant's goal, then, was to find some way to derive cause and effect without relying on empirical knowledge. Kant rejects analytical methods for this, arguing that analytic reasoning can't tell you anything that isn't already self-evident. Instead, Kant argued that we would need to use synthetic reasoning. But this posed a new problem - how can one have synthetic knowledge that is not based on empirical observation - that is, how can we have synthetic a priori truths. Kant's famous quote from the first third of the book is, “thoughts without content [are] empty, and intuitions without concepts [are] blind.”

Immanuel Kant, lecturing to Russian officers — by I. Soyockina / V. Gracov, the Kant Museum, Kaliningrad
Immanuel Kant, lecturing to Russian officers — by I. Soyockina / V. Gracov, the Kant Museum, Kaliningrad

Kant did not have any trouble showing that we do have synthetic a priori truths. After all, he reasoned, geometry and Newtonian physics are synthetic a priori knowledges and are fundamentally true. The issue was showing how one could ground synthetic a priori knowledge for a study of metaphysics. This led to his most influential contribution to metaphysics - the abandonment of the quest to try to know the world in itself, instead acknowledging that there is no way to determine whether something is experienced the way it is because that's the way it is, or because the faculties we have with which to perceive and experience are constructed such that we experience it in a given way. He demonstrated this with a thought experiment, showing that we cannot meaningfully conceive of an object that exists outside of time and has no spatial components. Although we cannot conceive of such an object, Kant argues, there is no way of showing that such an object does not exist. Therefore, Kant says, metaphysics must not try to talk about what exists, but instead about what is perceived, and how it is perceived.

This insight allows Kant to set up a distinction between phenomena and noumena - phenomena being that which can be experienced, and noumena being things that are beyond the possibility of experience - things in themselves. Nothing can be truly experienced or else you would experience the noumenon itself. The phenomenon is only the representation of the object/noumenon that a person receives through their sensibilities. The phenomenon is a representation of an object not the object itself, nothing more. Kant then discussed and expanded on the faculties of experience we have, and thus was able to come up with a system of metaphysics that applied to the world as we perceive it.

Kant termed his critical philosophy "transcendental idealism." While the exact interpretation of this phrase is contentious, one way to start to understand it is through Kant's comparison in the second preface to the "Critique of Pure Reason" of his critical philosophy to Copernicus' revolution in astronomy. Kant writes: "Hitherto it has been assumed that all our knowledge must conform to objects. But all attempts to extend our knowledge of objects by establishing something in regard to them a priori, by means of concepts, have, on this assumption, ended in failure. We must therefore make trial whether we may not have more success in the tasks of metaphysics, if we suppose that objects must conform to our knowledge" [Bxvi]. Just as Copernicus revolutionized astronomy by changing the point of view, Kant's critical philosophy asks what the a priori conditions for our knowledge of objects in the world might be. Transcendental idealism describes this method of seeking the conditions of the possibility of our knowledge of the world.

Kant's "transcendental idealism" should be distinguished from idealistic systems such as Berkeley's. While Kant claimed that phenomena depend upon the conditions of sensibility, space and time, this thesis is not equivalent to mind-dependence in the sense of Berkeley's idealism. For Berkeley, something is an object only if it can be perceived. For Kant, on the other hand, perception does not provide the criterion for the existence of objects. Rather, the conditions of sensibility - space and time - provide the "epistemic conditions", to borrow a phrase from Henry Allison, required for us to know objects in the phenomenal world.

Kant's Refutation of Idealism

In order to answer criticisms of the Critique of Pure Reason that transcendental idealism denied the reality of external objects, Kant added a section to the second edition (1787) entitled "The Refutation of Idealism" that turns the "game" of idealism against itself by arguing that self-consciousness presupposes external objects in space. Defining self-consciousness as a determination of the self in time, Kant argues that all determinations of time presuppose something permanent in perception and that this permanent cannot be in the self, since it is only through the permanent that one's existence in time can itself be determined. This argument inverted the supposed priority of inner over outer experience that had dominated philosophies of mind and knowledge since Descartes.

Kant's moral philosophy

Kant developed his moral philosophy in three works: Groundwork of the Metaphysic of Morals [3] ( (1785), Critique of Practical Reason [4] ( (1788), and Metaphysics of Morals [5] ( (1798).

Kant is known for his theory that there is a single moral obligation, which he called the Categorical Imperative, from which all other moral obligations are generated. He believed that the moral law must be a principle of reason itself, and could not be based on contingent facts about the world (e.g., what would make us 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.) Kant's categorical imperative was formulated in three ways, which he believed to be roughly equivalent (although many commentators do not):

  • The first formulation (Formula of Universal Law) says: "Act only in accordance with that maxim through which you can at the same time will that it become a universal law."
  • The second formulation (Formula of Humanity) says: "Act that you use humanity, whether in your own person or in the person of any other, always at the same time as an end, never merely as a means."
  • The third formulation (Formula of Autonomy) is a synthesis of the first two. It says that we should so act that we may think of ourselves as legislating universal laws through our maxims. We may think of ourselves as such autonomous legislators only insofar as we follow our own laws.

Example of the first formulation:

The most popular interpretation of the first formulation is called the "universalizability test." An agent's maxim, according to Kant, is his "subjective principle of volition" — that is, what the agent believes is his reason to act. The universalizability test has five steps:

  1. Find the agent's 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.

There are two types of contradiction that Kant thinks may arise with impermissible maxims. The first type he calls "contradictions in conception." Kant uses the example of a false promise to illustrate this. His imagined agent has the maxim: "I am going to lie so that someone will lend me money, because I am in need." Kant argues that universalizing this maxim would lead to a contradiction — that is, if everyone were to follow this maxim, and were to lie whenever in need, promises would mean nothing. So it would be contradictory or irrational to make a false promise to secure money, since your promise would simply be laughed at. Thus, acting on such a maxim is impermissible, which means we have a duty not to make false promises just to satisfy our needs. Incidentally, Kant believed that any maxim involving lying would lead to a contradiction, leading to his commitment to the view that we have a perfect (i.e. inviolable) duty not to lie.

The second type of contradiction Kant calls "contradictions in will," which arise when a universalized maxim would contradict something the agent would have to will as a rational being. Kant's example involves a self-reliant person who thinks everybody should mind their own business, and thus acts on the maxim: "Don't help others." In the imagined world where this is universalized, Kant thinks that this would necessarily contradict something any rational agent must will, namely that if one is in great need and could easily be helped by another, as a rational being he would have to will that the other person help him — but this universalized maxim contradicts that, thus leading to a contradiction in will, and showing that the policy, "Don't help others" is impermissible.

Example of the second formulation:

If I steal a book from you, I am treating you as a means only (to obtain a book). If I ask to have your book, I am respecting your right to say no, and am thereby treating you as an end-in-yourself, not as a means to an end.

Kant applied his categorical imperative to the issue of suicide in Groundwork of the Metaphysic of Morals, writing that:

[I]f a man is reduced to despair by a series of misfortunes and feels wearied of life, but is still so far in possession of his reason that he can ask himself whether it would not be contrary to his duty to himself to take his own life, he should ask himself a question. He should inquire whether the maxim of his action could become a universal law of nature. His maxim is: From self-love I adopt it as a principle to shorten my life when its longer duration is likely to bring more evil than satisfaction. It is asked then simply whether this principle founded on self-love can become a universal law of nature. Now we see at once that a system of nature of which it should be a law to destroy life by means of the very feeling whose special nature it is to impel to the improvement of life would contradict itself, and therefore could not exist as a system of nature; hence the maxim cannot possibly exist as a universal law of nature, and consequently would be wholly inconsistent with the supreme principle of all duty.

The theory that we have universal duties, which hold despite one's own inclinations or the desire to pursue one's own happiness instead, is known as deontological ethics. Kant is often cited as the most important source of this strand of ethical theory; in particular, of the theory of conduct, also known as the theory of obligation.

Kant, Anthropology, and Racism

Kant's moral philosophy has come under criticism as his lectures on anthropology have been further examined. The standard account is that Kant's universalism is at times marred by incorrect empirical views of non-whites, rather than by a developed philosophical doctrine of white supremacy.

Although Kant produced two writings on Anthropology (Anthropology From a Pragmatic Point of View, and On the Different Races of Man) this is almost wholly ignored in the modern evaluation of his historical importance and philosophical attitudes. One clear reason for this "voluntary omission" is the racism contained in his writing in this field:

The Negroes of Africa do not have a feeling of nature that rises above the mediocre. Mr. Hume invites anyone to quote a single example of a Negro who has exhibited talents. He asserts that among the hundred thousands of blacks who have been seduced away from their own countries, although very many of them have been set free, yet not a single one has ever been found that has performed anything great whether in art or science or in any other laudable subject; but among the whites, people constantly rise up from the lowest rabble and acquire esteem through their superior gifts. (see "Akademieausgabe von Immanuel Kants Gesammelten Werken"; Book II: "Precritical Writings II"; 1757-1777; "Observations on the Feeling of the Beautiful and the Sublime", page 253, lines 1 to 10; published on

Further reading

Any suggestion of further reading on Kant is doomed by the fact that his work has dominated philosophy like no other figure after him. Nevertheless, several guideposts can be made out. In Germany, the most important contemporary interpreter of Kant and the movement of German Idealism which he began is Dieter Henrich, who has some work available in English. P.F. Strawson's "The Bounds of Sense" (1969) largely determined the contemporary reception of Kant in England and America, but his positions have been challenged by a number of recent thinkers including Henry Allison, Paul Guyer, Robert Pippin, Terry Pinkard, and Batrice Longuenesse. This body of work has begun to lessen the divide between academic interpretations of Kant in the English speaking world and in Europe. John Rawls' Lectures on the History of Moral Philosophy, is particularly useful in its investigation of Kant's moral philosophy within the vicissitudes of ethical systems from Hume to Leibniz to Hegel. More recently, Gary Banham has published a key interpretation of Kant's practical philosophy that has corrected exclusive focus on the categorical imperative in favour of an inclusive comprehension of right and virtue. John McDowell is perhaps the most important contemporary analytic philosopher who explicitly builds upon Kantian themes. Howard Caygill's dictionary of Kantian terms is an excellent guide to the overall terrain of the influence and nature of Kant's concepts.

Allison, Henry. Kants Transcendental Idealism. Yale University Press, 2004.

Banham, Gary Kant's Practical Philosophy: From Critique to Doctrine Palgrave Macmillan, 2003.

Caygill, Howard A Kant Dictionary Blackwell, 1995.

Guyer, Paul. The Cambridge Companion to Kant. Cambridge University Press, 1992

Henrich, Dieter. The Unity of Reason: Essays on Kants Philosophy. Harvard University Press, 1994.

Kuehn, Manfred. Kant: A Biography. Cambridge University Press, 2001.

Korsgaard, Christine. Creating the Kingdom of Ends. Cambridge, 1996.

Longuenesse, Batrice. Kant and the Capacity to Judge. Princeton University Press, 1998.

McDowell, John. Mind and World. Harvard University Press, 1994.

Pippin, Robert. Idealism as Modernism. Cambridge University Press, 1996.

Pinkard, Terry. German philosophy, 1760-1860: The Legacy of Idealism. Cambridge, 2002.

Rawls, John. Lectures on the History of Moral Philosophy. Cambridge, 2000.

Strawson, P.F. The Bounds of Sense: an essay on Kant's Critique of Pure Reason. Routledge, 1989.

Works and links to texts, in English and German

External links

See also

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  • Immanuel Kant (1902) Reflexionen zur anthropologie. In Gesammelte Schriften., volume XV, pages 55-899. Hrsg. von der Kniglich-Preussischen Akademie der Wissenschaften zu Berlin, Berlin, 1902-
  • Brigitte Sassen (2000), ed., Kant's Early Critics: The Empiricist Critique of the Theoretical Philosophy
  • Kuehn, Manfred. Kant: A Biography. Cambridge University Press, 2002 ISBN 0521524067
  • "Meet Mr Green" (, The Economist, May 3, 2001, retrieved March 19, 2005be:Імануіл Кант

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