Isaiah Berlin was witness to a century. Born in Riga in the twilight of the Czarist empire, he lived long enough to see the Soviet state collapse. Biographer of Marx, scholar of the Romantic movement, and defer of the liberal idea of freedom against Soviet tyranny, Berlin was the presiding judge of intellectual life on both sides of the Atlantic. When he died in 1997, he was hailed as the most important liberal philosopher of his time. But Berlin's life was not only a life of the mind. From Albert Einstein to Virginia Woolf, Winston Churchill to Anna Akhmatova, his circle of friends constitutes a veritable who's who of twentieth-century art, politics, and philosophy. In this definitive work, the result of a remarkable ten-year collaboration between biographer and subject, Michael Ignatieff charts the emergence of a unique temperament and a singular vision.