The philosopher and historian Bernhard Groethuysen was an outstanding figure in German-French cultural transfer between the wars. At the same time, his historical works make him one of the trailblazers of the modern turn toward the history of culture and the history of mentalities. This is the first comprehensive biography of an intellectual who was both a scholar in the German tradition and a Parisian homme de lettres. It points up the links between Groethuysen's life and works and defines his place in the 20th century European history of ideas.