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Immanuel Kant
Immanuel Kant
(18th Century painting)

Immanuel Kant (1724 - 1804) was a German philosopher of the Age of Enlightenment. He is regarded as one of the most important thinkers of modern Europe, and his influence on Western thought is immeasurable. He was the starting point and inspiration for the German Idealism movement in the late 18th and early 19th Centuries, and more specifically for the Kantianism which grew up around him in his own lifetime.

His works, especially those on Epistemology, Metaphysics and Ethics, such as his masterworks the "Critique of Pure Reason" and the "Critique of Practical Reason", achieved a complete paradigm shift and moved philosophy beyond the debate between the Rationalists and Empiricists which had dominated the Age of Reason and the early Age of Enlightenment, and indeed to combine those two apparently contradictory doctrines.

His ideas and original thought have informed almost every philosophical movement since, and he continues to challenge and influence philosophy (in both the Analytic and Continental Philosophy camps) to this day.


Immanuel Kant was born on 22 April 1724 in the city of Königsberg (then the capital of Prussia, now modern-day Kaliningrad, Russia). He spent his entire life in and around his hometown, never traveling more than a hundred miles from Königsberg. His father, Johann Georg Kant, was a German craftsman and harness maker from Memel, Prussia; his mother, Anna Regina Porter, was born in Nuremberg, but was the daughter of a Scottish saddle and harness maker. He was the fourth of eleven children (five of whom reached adulthood). He was baptized as "Emanuel" but later changed his name to "Immanuel" after he learned Hebrew.

He was raised in a Pietist household (a strict Lutheran sect that stressed intense religious devotion, personal humility and a literal interpretation of the Bible), and accordingly received a strict, punitive and disciplinary education that favored Latin and religious instruction over mathematics and science.

Kant's elementary education was undertaken at Saint George's Hospital School, after which he was educated at the Pietist Collegium Fredericianum, where he remained from 1732 until 1740, and where he studied theology and excelled in the classics. Kant showed great application to study early in his life, and was enrolled in the University of Königsberg in 1740, at the age of 16.

There, under the influence of a young instructor, Martin Knutzen, Kant became interested in philosophy, mathematics, and the natural sciences, and, through the use of Knutzen's private library, grew familiar with the Rationalist philosophy of Gottfried Leibniz and Christian Wolff (1679 - 1754), as well as the natural philosophy and new mathematical physics of Sir Isaac Newton (1643 - 1727). Knutzen dissuaded the young scholar from traditional Idealism (i.e. the idea that reality is purely mental), which was negatively regarded by the whole philosophy of the 18th Century, and a chance reading of David Hume also raised his suspicions against Rationalism and he was soon to move away from his early Rationalist beliefs. He later admitted that reading Hume was what "first interrupted my dogmatic slumber".

The death of Kant's father in 1746 left him without income and interrupted his studies. For seven years, he worked as a private tutor in the smaller towns surrounding Königsberg, but he continued his scholarly research, and published several early works, mainly on scientific topics. 1749 saw the publication of his first philosophical work, "Gedanken von der wahren Schätzung der lebendigen Kräfte" ("Thoughts on the True Estimation of Living Forces").

In 1755, he presented a Latin treatise, "On Fire", to qualify for his doctoral degree, and he spent the next 15 years as a non-salaried lecturer at the University of Königsberg (dependent on fees from the students who attended his lectures). He lectured on Metaphysics, Logic, mathematics, physics and physical geography, and, despite a large teaching burden, continued to publish papers on various topics, including "Der einzig mögliche Beweisgrund zu einer Demonstration des Daseins Gottes" ("The Only Possible Argument in Support of a Demonstration of the Existence of God") in 1763 and other works on Logic and Aesthetics. He finally achieved a professorship of Logic and Metaphysics at Königsberg in 1770, at the age of 46, an established scholar and an increasingly influential philosopher.

For the next decade, Kant published almost nothing, and applied himself to the vexing issues of the Philosophy of Mind and to a resolution of the contradictions inherent in perception and conception as explained by the Rationalists and Empiricists, resisting all his friends' attempts to bring him out of his isolation.

The result was the "Kritik der reinen Vernunft" ("Critique of Pure Reason") of 1781, now widely regarded one of the most important and difficult books in Western philosophical thought. However, this long (over 800 pages in the original German edition) and dense book, written in a somewhat convoluted style was largely ignored upon its initial publication, and Kant, who was by then quite a popular author, was dismayed. He wrote the "Prolegomena zu einer jeden künftigen Metaphysik" ("Prolegomena to any Future Metaphysics") in 1783 as a summary and clarification of its main views, but it was only as a result of a series of widely read public letters on the Kantian philosophy published by Karl Reinhold in 1786, as a response to the Pantheism Dispute (a central intellectual controversy of the time), that Kant's reputation spread, making him the most famous philosopher of his era.

Undaunted by the negative initial response to his masterwork, Kant continued to publish papers throughout the 1780s, including a heavily revised second edition of the "Critique of Pure Reason". He also continued to develop his moral philosophy, notably in 1785's "Grundlegung zur Metaphysik der Sitten" ("Groundwork of the Metaphysics of Morals"), 1788's "Kritik der praktischen Vernunft" ("Critique of Practical Reason", known as the "second Critique") and 1797’s "Metaphysik der Sitten" ("Metaphysics of Morals"). The 1790 "Kritik der Urteilskraft" ("Critique of Judgment", the "third Critique") applied the Kantian system to Aesthetics and teleology (the philosophical study of design and purpose).

By the 1790s, there were several journals devoted solely to defending and criticizing the Kantian philosophy. But, despite his success, philosophical trends were moving in another direction, and many of Kant's most important disciples (including Karl Reinhold, Jakob Sigismund Beck and Johann Gottlieb Fichte) transformed the Kantian position into increasingly radical forms of Idealism, marking the emergence of the German Idealism movement. Kant opposed these developments and even publicly denounced Fichte in an open letter in 1799.

Kant continued writing until shortly before his death, although the Critiques remain the real sources of his influence. Only a life of extraordinary self-discipline enabled him to accomplish his task: he kept to such a strict routine that the residents of Königsberg quite literally set their watches by his schedule. He never married, was barely 5 feet tall, and extremely thin, and his health was never robust, but he attributed his longevity and his prodigious output to his invariable daily routine. Contrary to his dour reputation, though, Kant was actually very sociable, a witty and amusing conversationalist, an elegant dresser, and his lectures at the University of Königsberg, where he taught for over 30 years, were famous for their brilliance.

Towards the end of his life, Kant became increasingly anti-social and bitter over the growing loss of his memory and capacity for work. He became totally blind and finally died on 12 February 1804 in the beloved Königsberg where he had spent his entire life. He was buried in Königsberg Cathedral.

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Kant wrote a number of well-received and semi-popular essays on a variety of topics from science to history to religion to politics to anthropology, and by the 1770s he had become a popular author of some note, despite the difficulty and obscurity of his style. The philosophy for which he has become justifiably famous, though, dates largely from his middle and old age.

His first real philosophical work was 1749's "Gedanken von der wahren Schätzung der lebendigen Kräfte" ("Thoughts on the True Estimation of Living Forces"), and he continued publishing books and papers for the rest of his life, although with an eleven-year gap between 1770 and 1781 leading up to the publication of his masterwork, "Kritik der reinen Vernunft" ("Critique of Pure Reason"). This and the two succeeding Critiques, 1788's "Kritik der praktischen Vernunft" ("Critique of Practical Reason") and 1790's "Kritik der Urteilskraft" ("Critique of Judgment"), remain the real sources of his lasting influence.

In his Epistemology, Kant started with the traditional distinction between "truths of reason" (which Kant called analytic propositions, ones which are true simply by virtue of their meaning, and only elucidate or explain words e.g. "all bachelors are unmarried") and "truths of fact" (which Kant called synthetic propositions, ones which make claims beyond that e.g. "all bachelors are happy"). He added to this two other concepts: a priori knowledge (which comes purely from reasoning, independent of experience, and typically applies to analytic propositions) and a posteriori knowledge (which comes from experience alone, and typically applies to synthetic propositions).

On the one hand, Empiricism allows for synthetic propositions and a posteriori knowledge, and, on the other hand, Rationalism allows for analytic propositions and a priori knowledge. However, Kant maintained that the two could be combined, and that synthetic a priori statements were in fact possible, that there existed propositions which applied to the physical world but were not derived from the world, but which were established simply by argument. He argued that knowledge comes from a synthesis of experience and concepts: without the senses, we would not become aware of any object, but without understanding and reason we would not be able to form any conception of it.

He maintained that, although space and time are given to us as a priori pure intuitions, we grasp reality and make sense of the world through a basic conceptual apparatus, which involves several categories of thought. He divided these categories into four groups of three: quantity (unity, plurality, totality); quality (reality, negation, limitation); relation (substance, cause, community) and modality (possibility, existence, necessity).

Perhaps Kant's most original contribution to philosophy was the idea that it is the representation that makes the object possible, rather than the object that makes the representation possible. This introduced the human mind as an active originator of experience rather than just a passive recipient of perception, and placed the role of the human subject or knower at the center of inquiry into our knowledge.

However, he also set limits to knowledge. He distinguished between appearance (the world of phenomena) and reality (the world of noumena). Although our senses tell us that things exist outside of ourselves, the actual real substance of an object (what he called the "ding-an-sich" or thing-in-itself") was essentially unknowable. Thus, there may exist many things in the universe which we do not have the sensory or intellectual capacity to apprehend, and, although these things are real in themselves, they are not real "for us". We have certain predispositions as to what exists, and only those things that fit into these predispositions can be said to exist for us. This was something of a radical and revolutionary idea which does not seem to have occurred to anyone before Kant.

The (simplified) argument of the first "Critique", then, is that, while empirical objects, like books and chairs, are in some sense very real, they might not be "transcendentally real". Chairs are real insofar as they are objects that have to conform to our concepts, to our perceptual categories, but we cannot be sure that they are transcendentally real, because to be sure of this we would ourselves have to transcend our own perceptual limitations to confirm the "transcendental" existence of objects. Thus, "real objects", in Kant's view, are simply those that are subject to our perceptual categories: we cannot be sure that other non-empirical objects do not exist, but this should not worry us.

His doctrine of the "primacy of practical over pure reason", led to the later 19th Century doctrine of Voluntarism. He argued that, intellectually, humans are incapable of knowing ultimate reality, but this need not (and, Kant argues, must not) interfere with the duty of acting as though the spiritual character of this reality were certain. Thus, while Kant freely admitted that Newtonian physics was a clear and accurate depiction of the world of appearances, the world we are able to physically perceive, there was still room in his system for other concepts completely (such as free will, rational agency, God, good and bad, etc), but that these concepts could not be subjects of definite knowledge.

Kant argued that, while reason can be a helpful tool, it must be properly controlled so that we do not unreflectively accept things for which we have no evidence. What he calls the "critical method" is a philosophical approach that allows people to discover which questions reason can answer, and which ones it cannot. Thus, in his 1793 "Religion innerhalb der Grenzen der bloßen Vernunft" ("Religion within the Boundaries of Mere Reason"), Kant again encouraged us to give up things we do not need, namely religious practices that are unnecessary for true moral conduct.

Similarly, although reason can help us supplant unjust political regimes with better ones, for example, Kant did not believe that reason is an unqualified good, but must be employed critically in order to avoid heading down the wrong path. Although he objected to direct democracy as "necessarily a despotism", Kant foreshadowed Democratic Peace Theory in his 1795 essay "Zum ewigen Frieden" ("Perpetual Peace"), in which he posits that constitutional republics were one of several necessary conditions for a perpetual peace. Unlike many Enlightenment thinkers, he argued that real democracy is not only humane, but also in keeping with the basic human desire to pursue collective ends.

Like many philosophers before (and after) him, Kant was deeply dissatisfied with the purported solutions of other philosophers to the perennial problem of how to reconcile the apparently deterministic character of the physical world with the existence of human free will, which was necessary for the resolution of moral and ethical questions. These contradictions seemed especially stark in the wake of the great leap forward in the physical sciences during the 17th Century, in which scientists seemed largely agreed on the new findings, as compared to the chaotic battlefield of philosophy, where no philosopher seemed able to agree with any other. He was also concerned with how a God could fit in with an essentially mechanical and determined universe, and he was eager to confront the serious doubts about philosophy as an intellectual enterprise that the skepticism of David Hume had recently sown in the philosophical community as a whole.

Kant developed his moral philosophy in three main works: "Grundlegung zur Metaphysik der Sitten" ("The Fundamental Principles of the Metaphysics of Ethics": 1785), "Kritik der praktischen Vernunft" ("Critique of Practical Reason": 1788), and "Metaphysik der Sitten" ("Metaphysics of Morals": 1797). He started by observing that it is an observable empirical fact that people do in fact have moral and ethical views and, for them to have any meaning at all, people must have some element of free will.

His view of Ethics is deontological (i.e. it focuses on the rightness or wrongness of the actions themselves, as opposed to the rightness or wrongness of the consequences of those actions or the character of the actor, and holds that ethical rules bind people to an ethical duty). It is founded on his view of rationality as the ultimate good, and his belief that all people are fundamentally rational beings. He believed that morality was derived from rationality and that, just as rational thought leads us to an objective reality, it also leads us to an objective morality, which could be rationally supported.

His major contribution to Ethics was the theory of the Categorical Imperative, an absolutely universal, non-negotiable moral law which holds up regardless of context. At its simplest, it states that one should act only in such a way that you would want your actions to become a universal law, applicable to everyone in a similar situation (a kind of Moral Universalism or Moral Absolutism). Additionally, one must strive to treat others not as mere means, but as ends in themselves, so that (in stark contrast to Utilitarianism) it can never be right to manipulate, abuse or lie to individuals, even in the interests of others or even the perceived greater good. This latter maxim was, and remains, highly controversial when taken to extremes, but Kant insisted that it should remain sacrosanct. He asserted that each person is his own moral agent, and we should only be responsible for our own actions, not those of others.

According to Kant's "critical method", as described above, any attempts to prove God's existence are necessarily a waste of time, because our concepts only work properly in the empirical world and God is, by definition, a non-empirical entity. However, he justifies his own faith by arguing that, although it would be superstitious or irrational to have a belief on something which can actually be empirically proven or demonstrated, it is not irrational to have a belief on something that clearly cannot be proven either way (like the existence of God). This amounts to a kind of Fideism.

This, however, is very different from Kant's early metaphysical arguments in his pre-critical period. In his 1763 "Der einzig mögliche Beweisgrund zu einer Demonstration des Daseins Gottes" ("The Only Possible Argument in Support of a Demonstration of the Existence of God"), he first questions both the ontological argument and the argument from design for the existence of God (see the section on the Philosophy of Religion), before proposing his own solution (sometimes called the Kantian Moral Argument), that moral behavior would only be rational in our manifestly unfair world if there is a next life in which justice is administered.

Kant produced an early treatise on Aesthetics, "Beobachtungen über das Gefühl des Schönen und Erhabenen" ("Observations on the Feeling of the Beautiful and Sublime": 1763), and did not write on the subject again until the end of his career, in the "Kritik der Urteilskraft" ("Critique of Judgment": 1790). He claimed that judgments of taste are both subjective and universal: subjective in that they are responses of pleasure, and do not essentially involve any claims about the properties of the object itself; universal in that they are not merely personal, but must in a crucial way be disinterested. He divided the kinds of aesthetic response into those of the Beautiful (a pleasure in order, harmony, delicacy and the like) and the Sublime (a response of awe before the infinite or the overwhelming).

Although less well known, Kant also wrote on the sciences throughout his life. In an early scientific paper entitled "Allgemeine Naturgeschichte und Theorie des Himmels" ("General Natural History and Theory of the Heavens") of 1755, Kant postulated the origin of the solar system as a result of the gravitational interaction of atoms, anticipating Pierre-Simon Laplace's hypothesis by more than 40 years. He also correctly deduced that the Milky Way was a large disk of stars, which he theorized was also formed from a much larger spinning cloud of gas.

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