Affirming: Letters 1975-1997 by Isaiah Berlin (Chatto & Windus, £40) In a letter to Arthur Schlesinger in July 1978, Isaiah Berlin described himself as a “voyeur of history.” The definition seems particularly apt given Berlin’s position as a kind of godfather to 20th-century sceptical liberalism. Berlin had many interesting ideas to his name. His best, though, was a rejection of the idea of “positive freedom,” which requires state intervention of a kind many liberals would oppose. This and a host of other topics are written about with scrupulous attention to detail in this astounding book of letters—the fourth and final volume taking us up to Berlin’s death in 1997. The letters are addressed to a wide spectrum of well-known public figures, including Noam Chomsky, Prince Charles and Josef Stalin’s daughter, Svetlana Alliluyeva. As a philosopher, an authority on the history of ideas and, for a brief period, a diplomat, Berlin was equally comfortable pontificating from an ivory tower as he was holding court at a cocktail party. Through his close reading of mid-19th century Russian writers such as Alexander Herzen and Ivan Turgenev, Berlin spent his entire life attempting to understand the great paradox of human nature, in which selfish behaviour rubs shoulders with fellow-feeling. Modest, polite and beautifully written, these letters can be viewed as open-ended conversations with kindred spirits. They are also an important attempt to document the history of the late 20th century.