The immensely gifted Ignatieff has written a biography of Berlin that is clearly a work of love as well as scholarship. Ten years of interviews and access to private correspondence have resulted in a rich work that conceals none of Berlin's defining contradictions. An exile from the Soviet Union who became an enthusiastic Briton, a Jew torn between his Zionism and his British loyalties in World War II, a brilliant conversationalist and lover of parties, a university don on the threshold of politics, Berlin emerges from this account as a complex and increasingly wise man. Without writing a purely intellectual biography, Ignatieff emphasizes Berlin's antitotalitarianism and the essence of his political philosophy. Rooted in the Enlightenment, suspicious of Romanticism's political consequences, Berlin's liberalism passionately defended "negative liberty," or freedom from restraints and obstacles. As a corollary, negative liberty meant that the pluralism of beliefs and values could never be eliminated. And yet, Berlin cautioned, pluralism did not mean relativism. He firmly believed in ultimate "standards of evaluation . . . recognized as common by all human cultures." This beautifully written book -- entertaining, thoughtful, and moving -- is a fine achievement.