Ludwig Wittgenstein: * 26. April 1889 in Wien; † 29. April 1951 in Cambridge.

Tractatus logico-philosophicus: Logisch-philosophische Abhandlung.

Wittgenstein was an Austrian philosopher of the 20th century and one of the most important of his time. His writings contributed to the philosophy of logic, language and consciousness. Tractatus logico-philosophicus (1921) and Philosophical Investigations (1953, posthumously) became important points of reference for two philosophical schools, Logical Positivism and the Analytic Language Philosophy.