Immanuel Kant (22 April 1724 - 12 February 1804) was a German philosopher during the European enlightenment, working primarily in the field of metaphysics. His most prominent contributions to contemporary thought are his theories of metaphysics and epistemology, as well as ethics.
Philosophical and Theological Contributions
Kant's contributions to metaphysics and epistemology are often given secondary importance to the conception. However, his contributions to those fields were significant, as well as his contributions to ethics.
Categories of Knowledge
Kantian epistemology focuses on a distinction between two categories of statement, the synthetic and the analytic. Though Kant did not use this language, the two are often expressed as being properties of propositions. An analytic proposition is one which can be found to be true or false without reference to any other statement. A synthetic proposition is one which can only be found to be true or false with to other statements. Kant also distinguishes between statements which can be known to be true a priori and those which can only be known to be true a posteriori. A statement can be known to be true a priori if the discernment of its truth value can be assessed without any investigation of the physical world. A posteriori statements can only be found to be true or false upon observation of the physical world.
The most popular idea attributed to Kant is his conception of the 'categorical imperative', which he regarded as a means for assessing the viability of a statement as a potential moral law. That moral law, if it was found to be in compliance with the categorical imperative, could then be applied to maxims, or moral statements about the value of a particular action at a particular time. It can be found, in three formulations, in Groundwork for the Metaphysics of Morals.
The first formulation is popularly rendered as: Always act according to that maxim that you can at the same time will would become universal law. Kant did assert that there were certain acts which it was always necessary to do, in accordance with this imperative. Among these, a popular example which was, in his own time, criticized, was 'telling the truth', which Kant maintained an individual was always morally obliged to do.
The second formulation is popularly paraphrased as: See all rational beings not simply as means to achieve ends, but as ends in themselves. There are some concerns that have been raised by ethicists about what is regarded as a 'rational being', and what prescribed relationship such a maxim would entail, or permit, with respect to non-rational beings.
The third formulation is popularly rendered: All maxims which stem from autonomous legislation ought to harmonize with a possible realm of ends as with a realm of nature. It is generally regarded as a sort of synthesis, or middle-ground, between the first and second formulations.
(1781) Critique of Pure Reason
(1788) Critique of Practical Reason
(1790) Critique of Judgment
(1797) Metaphysics of Morals