1. an idea, or proposition that is opposite to or contradicts another proposition or idea. 2. in philosophy, this term refers to the second stage of a dialectical process based on proposition, contradiction, and the reconciliation of them (thesis, antithesis, and synthesis). Often associated with German philosopher Georg Wilhelm Friedrich Hegel (1770-1831) in relation to his theory of the dialectical development of ideas. See also dialectical materialism.
ANTITHESIS: "An antithesis is an idea that opposes the thesis, or main idea."