British political philosopher and historian. Born in Latvia and educated at Corpus Christi College, Oxford, Berlin held Fellowships at All Souls and New College, before becoming President of Wolfson College, Oxford, from 1966 to 1975. He is best known in political philosophy for the distinction between negative and positive liberty, drawn in his Two Concepts of Liberty (1959): that is, although any statement about liberty ought to specify both what one is free to do (positive) and what one is free from in doing it (negative), nevertheless different political philosophies give the one much more importance than the other. Thus liberalism dwells on the virtues of being free from legal and social constraint; idealist and Hegelian theories stress that the most important kinds of freedoms and opportunities can only exist in a structured society, so that the constraints needed to produce such societies may be a necessary means to the best ends. Berlin also energetically opposed the valuefree, historicist view of history of Marxism, notably in Historical Inevitability (1954).