 Throughout the 1930s Berlin was deeply involved in the development of what became known as Oxford philosophy, or ordinary language philosophy; his friends and colleagues included J. L. Austin, A. J. Ayer and Stuart Hampshire, all of whom met regularly (with others) in Berlin’s rooms to discuss philosophy. However, he also evinced an early interest in a more historical approach to philosophy, and in social and political theory, reflected in his lectures and reviews of the 1930s, as well as in his intellectual biography of Karl Marx (1939), still in print, in its fifth edition (2013), over eighty years later.