German philosopher Jürgen Habermas has died at age 94. The Frankfurt School thinker was best known for his theory of communicative action and critical social theory. His academic career spanned over five decades, beginning with his appointment to Frankfurt University in 1964 where he succeeded Max Horkheimer as chair of philosophy and sociology.

Habermas gained prominence in the 1960s as a key intellectual figure during the German student movement. While supporting the movement's goals, he opposed its radical turn. His 1968 work "Erkenntnis und Interesse" established his reputation in epistemology and social theory. In 1971, he moved to Munich to direct the Max Planck Institute, where he developed his major theoretical works.

His magnum opus "Theorie des kommunikativen Handelns" was published in 1981, synthesizing his work on language, rationality, and social interaction. Habermas returned to Frankfurt in 1983 and remained there until his retirement in 1994. Throughout his career, he influenced fields from political philosophy to sociology, becoming one of the most cited philosophers of the 20th century.