Kant and his philosophy
Kant defined the Enlightenment, in the essay "Answering the Question: What is Enlightenment?", as an age shaped by the motto, "Dare to know" (latin: Sapere aude). This involved thinking autonomously, free of the dictates of external authority. Kant's work served as a bridge 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 pepe.

The two interconnected foundations of what Kant called his "critical philosophy" of the "Copernican revolution" which he claimed to have wrought in philosophy were his epistemology (or theory of knowledge) of Transcendental Idealism and his moral philosophy of the autonomy of reason. These placed the active, rational human subject at the center of the cognitive and moral worlds. With regard to knowledge, Kant argued that the rational order of the world as known by science could never be accounted for merely by the fortuitous accumulation of sense perceptions. It was instead the product of the rule-based activity of "synthesis".

This consisted of conceptual unification and integration carried out by the mind through concepts or the "categories of the understanding" operating on perceptions within space and time, which are not concepts, but forms of sensibility that are necessary conditions for any possible experience. Thus the objective order of nature and the causal necessity that operates within it are products of the mind in its interaction with what lies outside of mind (the "thing-in-itself").

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 only in a good will. A good will is one that acts in accordance with universal moral laws that the autonomous human being freely gives itself. These laws obligate people to treat other human beings as ends rather than as means to an end.

These Kantian 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 makes a constitutive contribution to its knowledge, which is therefore subject to limits that cannot be overcome, that morality is rooted in human freedom and acting autonomously is to act according to rational moral principles, and that philosophy involves self-critical activity, irrevocably reshaped philosophy.

Biography

Birth and youth
Immanuel Kant - who was baptized as "Emanuel" but later changed his name to "Immanuel" - was born in 1724 in Königsberg, Germany (now Kaliningrad, Russia). He spent his entire life in and around his hometown, the capital of East Prussia at that time. His father was a German craftsman from Memel, Germany's northeasternmost city (now Klaipeda, Lithuania). In his youth, Kant was a solid, albeit unspectacular, student.

He was raised in a Pietist household, a then popular Lutheran reform movement that stressed intense religious devotion, personal humility and a literal reading of The Bible. Consequently, Kant received a stern education -- strict, punitive, and disciplinary -- that favored Latin and religious instruction over mathematics and science. Kant later described this period as a time of unhappiness.

The young scholar
Kant 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 the developments of British philosophy and science and who introduced Kant to the new mathematical physics of Newton. 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 and became a university lecturer in 1755. From this point on, Kant turned increasingly to philosophical issues, although he would continue 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.

The critical turn
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. He also credited David Hume with awakening him from "dogmatic slumber" (circa 1770). Kant would not publish another work in philosophy for the next eleven years.

Kant spent his silent decade working on a solution to the problems posed. When he 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 a dry, scholastic style.

It received few reviews, and these failed to recognize the Critique's revolutionary nature. Kant was disappointed with the work's reception. Recognizing the obscurity of the original treatise, he wrote the Prolegomena to any Future Metaphysics in 1783 as a summary of its main views and he encouraged his friend, Johann Schultz, to publish a brief commentary of 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?"; 1785's 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 Lessing (a distinguished philosopher of the period) of Spinozism. Such a charge, tantamount to atheism, was vigorously denied by Lessing's friend Moses Mendelssohn, and a bitter public dispute arose between them.

The controversy gradually escalated into a general debate over the values of the Enlightenment and 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
Immanuel Kant, detail from a 1791 watercolour by Gottlieb DoepplerKant published a second edition of the Critique of Pure Reason 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. This marked the emergence of German Idealism. Kant was against 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, turned for the worst and he died in 1804. His unfinished final work, the fragmentary Opus Postumum, was (as its title suggests) published posthumously.

Erroneous beliefs
A variety of popular beliefs have arisen concerning Kant's biography and legend. 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.

Another common myth concerns Kant's personal mannerisms. 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. Again, this is only partly true. While still young, Kant was very gregarious and, though he never married, he remained fond of dinner parties through most of his life. Only later in his life, under the influence of his friend, the English merchant Joseph Green, did Kant adopt a more regulated lifestyle[citation needed].

Kant's moral philosophy
Kant developed his moral philosophy in three works: Groundwork of the Metaphysic of Morals (1785), Critique of Practical Reason (1788), and Metaphysics of Morals (1798).

The three works proceed by a method of taking the "rational [, obvious, and everyday] knowledge of the moral to the philosophical [knowledge of the moral]" in the Groundwork - and also making necessary the moral works that followed; and then, in those latter works, following a method of using "practical reason", 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 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, which is derived from the concept of duty. It is from the Categorical Imperative that all other moral obligations are generated, and by which all moral obligations can be tested. 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. 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 as if the maxim of thy action were to become by thy will a universal law of nature."
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, in a possible Kingdom of Ends. 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. 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.

Political philosophy
Kant was an advocate of constitutional republicanism. He opposed democracy, believing that majority rule posed a threat to individual liberty. He says, "Democracy is necessarily despotism, as it establishes an executive power contrary to the general will; all being able to decide against one whose opinion may differ, the will of all is therefore not that of all: which is contradictory and opposite to liberty." (Perpetual Peace, II, 1795)

Influence
Kant's most powerful and revolutionary effect on philosophy, which changed forever its meaning, modes of thinking, and language(s), was not "positive" in the sense of producing specific assertions about the world that have become accepted truths, as in the positive sciences. Rather it was "negative" in the sense of restricting the areas about which such knowledge was possible — by making philosophy "critical" and self-critical.

Kant's idea of "critique" was to examine the legitimate scope of the mind or of knowledge. In this regard the "critique of pure reason", which was also the title of his most important work (see below and Critique of Pure Reason), meant examining what certain and legitimate knowledge human beings could arrive at simply by thinking about things independently of experience and perception, with his conclusion being: not very much.

Prior to Kant, the entire mode of functioning of most philosophy was drawing conclusions about the nature of the universe, of God, or of the soul simply by logical thinking about them, by what seemed to make sense through "a priori" thinking, i.e. thinking on purely logical grounds. For this sort of thinking it must be the case that God or the universe is this way or that way, because it makes sense logically.

But, in the history of philosophy, for every philosophical theory that God or the universe or the mind must be one way, some philosopher arrived at another theory stating that it must be precisely the opposite way. Kant called this unproductive, unresolvable, back-and-forth, dogmatic thinking the "dialectic of pure reason". That is, it was an inevitable consequence of trying to arrive at knowledge on purely logical grounds independently of experience or of scientific knowledge based on the evidence of the senses.

For Kant, this entire style of pursuing knowledge was bankrupt and must be abandoned. According to Kant, philosophy must henceforth operate within the narrow "limits of pure reason" and recognize that most positive knowledge could come only through the sciences based on sense perception and not through metaphysics, which was about things of which we could never have direct sense perception.

The philosopher Arthur Schopenhauer was strongly influenced by Kant's transcendental idealism. Schopenhauer accepted the distinction between two kinds of knowledge: the world perceived as phenomenon and also thought of as non-phenomenon (thing-in-itself). For Kant, the thing-in-itself cannot be an object of perceived experience. But, for Schopenhauer, the thing-in-itself can be experienced as the basis of that which, in animal life, is called "will," "desire," or urge. Schopenhauer claimed that the will as such, as thing-in-itself, is the inner, essential nature of the whole experienced world.

Some important philosophers and schools of thought, such as German Idealists, neo-Thomists and other theologically oriented philosophers, and Heidegger's "fundamental ontology" have refused to accept the limitations that Kant imposed upon philosophy and attempted to come up with new metaphysical systems about "the Absolute", "God", or "Being" , although even these philosophers have generally tried doing so by taking Kant into account.

Over-all, however, post-Kantian philosophy has never been able to return to the style of thinking, arguing, and asserting conclusions that characterized philosophy before him. In this way, Kant was correct in asserting that he had brought about a "Copernican revolution" in philosophy. According to Kant, Copernicus's revolution in the understanding of the cosmos lay in taking the position of the observer into account. This explained why it looks as though the sun revolves around the earth even though in reality the earth revolves around the sun.

Taking the observer's position into account prevents the unaware projection of the observer's perception or point of view onto the picture of the universe. Kant saw his own Copernican revolution in philosophy, analogously, as consisting in taking the position of the knower into account and thereby preventing the unaware projection of the knower's way of thinking ("pure reason") onto the philosophical map of reality.

According to Kant, it was philosophers unawarely doing this that had created the illusions of metaphysics that dominated the prior history of philosophy. Kant saw this revolution, in turn, as being part of "Enlightenment" (as conceived of in the Age of Enlightenment) and the creation of an enlightened citizenry and society freed from dogmatism and irrational authority.

Kant's wider influence not only in philosophy but in the humanities and social sciences generally lies in the central concept of the Critique of Pure Reason, namely that it is the synthesizing, unifying, constitutive activity of the subject of knowledge that is at the basis of our having an ordered world of experience and of the objects of knowledge themselves. This idea has spread out through many intellectual disciplines in which it has manifested itself in different forms, for example:

1. from Marx's notion, in social theory, of the constitutive role of human labor in the creation of history and society
2. through Freud's notion, in psychology, that the activity of the ego produces the reality principle
3. through Durkheim's notion, in sociology, that society creates collective consciousness through social categories
4. through Chomsky's notion, in linguistics, of transformational grammar
5. to current notions, in several of the humanities and social sciences, regarding the "social construction of reality" (Berger & Luckmann, 1966).
6. In this way Kant's conception of synthesizing, ordering mental activity has become central to modern intellectual culture.

Tomb
His tomb and its pillared enclosure outside the cathedral in Kaliningrad are some of the few artifacts of German times preserved by the Soviets after they conquered the city 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. Near his tomb is the following inscription in German and Russian, taken from the "Conclusion" of his Critique of Practical Reason"