Kant, Immanuel

Kant, Immanuel (1724–1804), German philosopher. He published his first considerable work, A General Natural History of the Heavens, in 1755. His Critique of Pure Reason appeared in 1781 (second edition in 1787), Prolegomena to Any Future Metaphysics in 1783, Fundamental Principles of the Metaphysic of Ethics in 1785, Metaphysical Rudiments of Natural Philosophy in 1786, Critique of Practical Reason in 1788, Critique of Judgement in 1790, and Religion within the Boundaries of Pure Reason in 1793.

In Kant's philosophy, knowledge is the outcome of two factors, the senses and the understanding. Space and time are essential conditions of knowledge, although they exist only as forms of our consciousness. These forms, continuous and infinite, provide the possibility of unifying our individual perceptions, and the unification is effected by the understanding. This act of synthesis Kant analyses into twelve principles or ‘categories’, or laws of thought. The categories are to the understanding very much what time and space are to the consciousness. They include such notions as quality, quantity, and, notably, causation. The external world is thus the product of sensations conditioned by the forms of consciousness and linked by thought according to its own laws.

Where metaphysics fails us, practical reason comes to our aid. The moral consciousness assents to certain ‘categorical imperatives’, such as ‘do not lie’. Interpreted as a practical rule of conduct, the moral law bids you do all in your power to promote the highest good of all human beings. This is not realizable unless the course of the world is itself guided by moral law, by a moral Master of the universe, whose existence we are driven to assume. But metaphysics places religion and morality outside the province of knowledge, and in the region of faith.

Kant's philosophy was developed and profoundly modified by Fichte, Schelling, and Hegel. In Britain, Coleridge and Carlyle valued Kant's criticism of the empirical philosophy (and the atheism) of the 18th cent., particularly that of Hume.