Thinking theTwentieth Century, Tony Judt\'s final work, emerged out of trying circumstances. In 2008, the polemicist, historian and author of Postwar, was diagnosed with ALS, an incurable degenerative disease. At the time, Judt, who died in August 2010 (aged 62), had been contemplating a substantial work on 20th-century social thought; but his physical condition soon made writing, in the traditional sense, an impossible task. Instead, he teamed up with Timothy Snyder, a young historian of Eastern Europe, for a series of loosely structured chats on the contours of 20th-century history. The book that resulted is an often bracing tour d\'horizon of the ideas and political ideologies that tormented and defined the last century. Judt and Snyder go back and forth about a myriad of topics: the role of intellectuals; the fate of Mitteleurope\'s Jewish culture; the allure of communism and fascism; the fortunes of liberalism against totalitarianism; the historian\'s craft; Israel and US foreign policy - Judt is scathing about both; and the prospects for social democracy in the 21st century. Snyder guides the dialogues, but there is still organic disorder to the proceedings: we hear the ebb and flow of real conversation. The subject of intellectuals - their virtues and, more often, their vices - takes up a good bulk of these pages. Judt excoriates US liberal thinkers who supported - and the policymakers who carried out - the Iraq war. For Judt, it was a replay of the habits of mind that tarnished so much of 20th-century intellectual life: \"Once again, other people\'s ordeals are being justified as History\'s way of delivering a new world.\" It was merely a continuation of a dismal tradition. \"The intellectual sin of the [20th] century,\" Judt tells Snyder, was \"passing judgment on the fate of others in the name of their future as you see it, a future in which you have no investment, but concerning which you claim exclusive and perfect information.\" In earlier works like Past Imperfect and The Burden of Responsibility, Judt wrote harshly about the blindness of Sartre and other Left Bank intellectuals about Stalin\'s crimes. Judt is a moralist, and a certain arrogance colours his words. But he is often at pains to situate his views in the tumultuous context of 20th century. A man of the left, Judt liked to argue against the left. The son of Eastern European émigré Jews, Judt grew up in East London. His father was a diehard socialist who had only contempt for communists; in some ways, so too does the son. But Judt acknowledges the importance of communism, whatever its flaws, as an ideological project. In an exchange about Eric Hobsbawm, the renowned historian and decades-long member of the defunct British Communist Party, Judt observes, \"You cannot fully appreciate the shape of the 20th century if you did not once share its illusions, and the communist illusion in particular.\" After all, \"Marxism is a marvellously compelling account of how history works, and why it works.\" Judt endorses Marxism\'s version of history as a chastisement \"to liberals and progressives who assert that all is for the best\". Against this, Marx \"offers a powerful narrative of suffering and loss, deterioration and destruction\". But Snyder poses an interesting counter argument: if there are intellectual advantages to having been a Stalinist, then logic suggests there might be methodological gains to be had from being an ex-Nazi. Judt will have none of it. There are no Nazi Eric Hobsbawms, he says: \"I simply cannot think of a single Nazi intellectual whose reasoning holds up as an interesting historical account of 20th-century thought.\" The historian was nothing if not bold in his sweeping dismissals of ideas he disagreed with.