Sidney Hook is a uniquely fascinating figure in American intellectual history. He attempted to serve as a bridge between two fundamentally different worlds that he saw as entirely compatible - American pragmatist philosophy and revolutionary Marxism. On paper, his ideas make a lot of sense - it doesn't take much of an imagination to reconcile John Dewey's instrumentalism with Marx's celebrated final thesis on Feuerbach. But as history had it, his worlds were moving rapidly apart, and the tectonic shifts of the 1930s seem to have torn apart the man who was bridging the gap. In the post-war period he would end up as a rather uninteresting pragmatist philosopher and anti-Communist crusader, who said a lot of things that look quite silly from 2012. He even voted for Nixon. But to paraphrase the famous line about Hitchens, before he was a slug he was a butterfly. Hook wrote two books on Marx that would be arguably the strongest in the American Marxist tradition: "Towards the Understanding of Karl Marx: A Revolutionary Interpretation" (1933), and "From Hegel to Marx" (1936).Hook was a revolutionary socialist from his teenage years in Brooklyn. These politics were on a collision course with American philosophy when he studied at City College under the naturalist philosopher Morris Cohen, and went on to graduate study at Columbia with the quintessential American pragmatist, John Dewey. Hook would begin studies quite skeptical and combative of Dewey, yet come to view Dewey's pragmatism as fundamentally compatible with his radical perspective. He would eventually do everything in his power to persuade his mentor to embrace Marx. Dewey always resisted, although it is unclear to what extent he ever seriously studied Marx - he once claimed to have not read Marx, which would be incredible if true. Years later Hook did, however, convince Dewey to serve on the defense committee of Leon Trotsky, when he faced the trumped up charges of the Stalinist regime.While studying under Dewey, Hook was immersed in Lenin, translating his volumes to English, hailing his revolutionary action while expressing qualms about his epistemology. He would come to conclude that "Marxism and pragmatism required another to realize their respective promise", a view that he sharpened in a series of contentious exchanges with Max Eastman. In addition to Lenin, having traveled to Germany and the Soviet Union, Hook was greatly influenced by Karl Korsch and Georg Lukacs, two Western Marxists who central in reconnecting Marx to the Hegelian dialectic. All the while, Hook was a fellow traveler in the Communist Party, for instance supporting William Foster's 1932 presidential campaign. But just as his Marxism was rejected by his academic colleagues (Hook would land a job at NYU), his pragmatist instrumentalism was increasingly attacked by the increasingly bureaucratic and Stalinist party, which would eventually brand him "one of the most dangerous neo-revisionists in America."After breaking with the Communist Party, Hook was instrumental in attempts to create an independent American revolutionary socialism, first in founding the American Workers Party, with A.J. Muste, and then in orchestrating its merger with the Trotskyists, and finally with the Socialist Party. Thus, Hook and Dewey both ended up supporting the 1936 candidacy of Norman Thomas, but by completely different routes.Of course, such unity would not last long. The strain of factional disputes, increasing Stalinist "totalitarianism", and the rise of fascism would lead Hook to retreat from political activity to philosophy, and then ultimately to his transformation in the post-war period. I still find the reasons for such a profound transformation a little puzzling, and this is the weakest element of Phelps' account. But in terms of teaching us about the Young Sidney Hook, Phelps does admirably in rescuing the early work that has been underappreciated in the American Marxist tradition.Phelps book, in addition to Hook's primary writings, are essential to anyone interested in Marxism's relation to pragmatism, and even Marxism's relation to America more generally.