and together with Weber one of the principal founders of sociology as a distinct discipline. A cosmopolitan, Simmel studied at Berlin, where he continued to teach, unpaid, for many years (he had a considerable private fortune), only achieving an academic post as professor in Strasbourg as late as 1914. Erratically brilliant, he was described by Ortega y Gasset as an academic squirrel, and wrote about a wide variety of philosophical, sociological, cultural and historical matters. Books included Social Differentiation (1890), The Philosophy of Money (1900), Sociology: Investigations on the Forms of Sociation (1908), as well as works on Rembrandt and Goethe.