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Immanuel Kant



The Proceedings of the Friesian School, an electronic journal of philosophy, has an excellent section on the thought of Kant.
Immanuel Kant
Kantian Ethics Homepage
Kant on the Web


Critique of Pure Reason
Critique of Practical Reason
Critique of Judgement
The Metaphysical Elements of Ethics
The Science of Right

Immanuel Kant, widely acknowledged to have been one of the greatest of all philosophers, was born in Königsburg, East Prussia. At the age of 8 he entered the Collegium Fridiricianum, a pietistic Latin school; he remained there for 8 1/2 years and then entered the University of Königsberg in 1740 to study philosophy, mathematics, and physics. In 1756 he was granted a degree and made a lecturer, and in 1770 he became a professor.

Kant's thought was mainly influenced by the rationalism of Gottfried Wilhelm von Leibniz and Christian Wolff and the empiricism of David Hume. His greatest work, the Critique of Pure Reason (1781), is a synthesis of rationalism and empiricism, both of which in themselves, he believed, gave a one-sided view of knowledge. To understand this Critique one needs to understand Kant's logical system. He divides all judgements into a) analytic or synthetic judgements and b) a priori or a posteriori judgements. A judgement is analytic if its negation is a logical absurdity. Judgements about empirical matters are synthetic, which can be denied without contradiction. A priori judgements are independent of experience; all analytic judgements are a priori. Therefore there are three classes of judgements: a)analytic a priori, b) synthetic a posteriori, and c) synthetic a priori. Synthetic a priori judgements occur in pure mathematics and natural science, and one of his tasks in the Critique of Pure Reason is to show how they are possible.

Kant begins by distinguishing between perceiving and thinking, which are attributed to two distinct faculties of the mind, sense and understanding. Every judgement applies a concept to a particular; apprehension of particulars belongs to the faculty of sense, apprehension of concepts belong to the understanding. There are three types of concepts; a posteriori concepts are abstracted from sense perception and applicable to it, a priori concepts are not abstracted from sense perception but are applicable to it, and Ideas, which are independent of sense perception. He now asks if there are objects other than sense perception which the concepts of mathematics characterize, to which he answers that space and time are a priori and particulars rather than general notions. Arithmetic describes the structure of time with its repetition of units, and geometry describes the structure of space. Mathematical synthetic a priori judgements are then possible because they apply a priori concepts to the a priori particulars of space and time.

Kant goes on to show that science and common sense knowledge of fact also employ synthetic a priori judgements. He argues that causality is an a priori concept, because we do not abstract the concept of causality from perception. We do apply causality to perception, and concepts which are applicable to perception Kant calls Categories. There are a total of twelve categories--

a) Categories of quantity: Unity, Plurality, Totality
b) Categories of quality: Reality, Negation, Limitation
c) Categories of relation: Substance and Accident, Causality and Dependence, Community or Interaction
d) Categories of modality: Possibility--Impossibility, Existence--Non-existence, Necessity--Contingency
Synthetic a priori judgements consist in applying the Categories to sensory data in space and time, or the "perceptual manifold." Application of the Categories allows us to realize physical objects as capable of causal relations and interactions with other objects. Since applying the Categories makes us aware of objects, synthetic a priori judgements express the conditions under which objective experience is possible, and are the presuppositions of our apprehension of objects of science and common sense. Kant legitimates the application of the Categories to objects by reasoning that to be an object is simply to be capable of being characterized by the Categories. Since we categorize perceptual material located in space and time, knowledge is the product of perceiving and thinking. What exist apart from space, time, and the Categories are "things in themselves," or "noumena," to which we cannot apply the Categories.

Kant derives the Ideas from the possible forms of logical inference. We can always go on asking to have the premises of our inferences deduced from higher premises without limit. When we assume this potentially infinite series is actually given in its totality, an Idea is formed. Kant recognizes three Ideas; a) of the absolute unity of the thinking subject, b) of the absolute unity of the sequence of the conditions of appearance, and c) of the absolute unity of the conditions of objects of thought in general. Each Idea provides the subject matter of a metaphysical discipline, the first the subject matter of speculative psychology, the second of speculative cosmology, the third of speculative theology. Kant claims that all metaphysical knowledge of matters of fact is deducible from synthetic a priori principles. If the Categories are taken as characterizing things in themselves, or the Ideas are taken as characterizing something that is given in experience, metaphysics becomes spurious. The mistaken employment of Categories and Ideas leads to fallacies, one of which is the ontological argument for the existence of God. This argument tries to deduce God's existence from the fact that we can think of a perfect being, since lack of existence would be imperfection. Kant's reply to this argument is that existence is not a predicate.

In the Critique of Practical Reason Kant's concern is with the synthetic a priori principles which underlie our knowledge of what we ought to do. Kant creates his maxim, the general rule that an agent would formulate in justifying an action. He argues that a person's maxim is moral if it conforms to the moral law, or the "categorical imperative," which is derived as such; the maxim of my action, and therefore the action performed in accordance with it, is moral if and only if I can will that it should become a universal law. Put another way, Kant writes, "Act in such a way that you treat humanity both in your own person and in the person of all others, never as a means only but always equally as an end."

The commitment to the categorical imperative is objective. The Idea of freedom, Kant states, is not only demanded by a sense of duty, but is also compatible with the law of causality. Man as a phenomenal being is causally determined, but as a noumenal being he is free. He cannot know what his freedom is, but he knows that he is free. The nature of moral freedom is a mystery. To Kant morality doesn't need a being above man for man to recognize his duty, but morality gives rise to the assumption that virtue is somehow correlated with happiness, and suggests the Idea of a power that correlates them. Faith explains the mysterious consistency between moral freedom and causally determined nature, and to have made room for faith in the existence of God, Kant believes, is a greater achievement than to have provided fallacious proofs of it.

The Critique of Judgement is concerned with discovering subjective principles which are at the root of our search for systematic explanations of natural phenomena and our apprehension of beauty. Kant inquires about purpose and purposiveness. The notion of purpose is involved in any scientific explanation. We look for a systematic unity in the empirical laws we discover. Kant considers particular fields of inquiry and the teleological explanations sometimes used in them. The notion of purposes in Nature is an Idea, but as an Idea it has, unlike the Categories, no objective application. The teleological explanations foster the assumption of an omniscient being, but not even the most complete teleology amounts to a proof of God's existence, since teleological principles are merely subjective expressions.

Kant defines beauty as "the form of purposiveness in so far as it is perceived apart from the presentation of a purpose." The unity of aesthetic experience is due to the interplay of the faculties of perception and imagination with the faculty of understanding. An aesthetic judgement also claims that the beautiful object is connected with a pleasurable feeling, and that it pleases universally. This universality is merely a subjective foundation in our cognitive faculties, similar to teleological explanations.

Kant's influence has been very strong on the areas of mathematics and ethics, and had considerable influence on the rise of German idealism in Fichte and Hegel.

1996 Grolier Multimedia Encyclopedia, Copyright 1996 Grolier Interactive, Inc.

The Concise Encyclopedia of Western Philosophy and Philosophers, J. O. Urmson and Jonathan Rée, editors. London: Unman Hyman, 1991.