Isaiah Berlin began his academic career as a philosopher, became an historian of ideas, and was elected to a professorship in social and political theory at Oxford. But none of these labels quite succeeds in categorising him, because the particular character of his interests and methods escapes easy definition. 

The label most often applied to Berlin is ‘historian of ideas’, and it is certainly true that much of his work is devoted to the discussion of eighteenth- and nineteenth-century social and political thinkers in Europe, including Russia, with the Enlightenment and its critics a recurring theme. But his interest