German physician and philosopher who became one of the most popular exponents of 19th-century scientific materialism.

The younger brother of the playwright Georg Büchner, Ludwig became a lecturer in medicine at the University of Tübingen, but the outspoken materialism of his masterpiece, Kraft und Stoff (1855; Force and Matter), caused such an outcry that he was forced to resign. He retired to his hometown of Darmstadt and practiced medicine there while continuing to expound his materialistic and atheistic views in numerous publications.

Büchner's materialistic interpretation of the universe in Kraft und Stoff created an uproar for its rejection of God, creation, religion, and free will and for its explanation of mind and consciousness as physical states of the brain produced by matter in motion. His continued defense of atheism and atomism and his denial of any distinction between mind and matter (Natur und Geist, 1857; “Nature and Spirit”) appealed strongly to freethinkers, but dialectical materialists condemned his acceptance of competitive capitalism, which Büchner viewed as an example of Charles Darwin's “struggle for survival.” An English translation of his Die Stellung des Menschen in der Natur (1869) appeared as Man, Past, Present and Future (1872).