in philosophy, contradiction, real or apparent, between two principles or conclusions, both of which seem equally justified; it is nearly synonymous with the term paradox. Immanuel Kant (Kant, Immanuel), the father of critical philosophy, in order to show the inadequacy of pure reason in the field of metaphysics, employed the word antinomies in elaborating his doctrine that pure reason generates contradictions in seeking to grasp the unconditioned. He offered alleged proofs of the two propositions that the universe had a beginning and is of finite extent (the thesis) and also of a contrary proposition (the antithesis). Similarly, he offered proofs both for and against the three propositions: (1) that every complex substance consists of simple parts; (2) that not every phenomenon has a sufficient “natural” cause (i.e., that there is freedom in the universe); and (3) that there exists a necessary being, either within or outside the universe. Kant used the first two antinomies to infer that space and time constitute a framework imposed, in a sense, by the mind. Kant's “Copernican Revolution” was that things revolve around the knower, rather than the knower around things. He resolved the four antinomies by drawing a distinction between phenomena (things as they are known or experienced by the senses) and noumena (things in themselves; see noumenon). Kant insisted that we can never know the noumena, for we can never get beyond phenomena.

In the 20th century more specific suggestions for resolving the antinomies arose. Because the philosophical significance of these possible resolutions continues to be debated, however, the force of Kant's case against pure reason is yet to be assessed.