Joel Colton has succeeded in an exhaustive review of Blum's remarkable political life against the background of the shifting trends of French politics. Of middle class origins, Blum turned to politics as a sequel to the Dreyfus affair. He saw in socialism a program by which the French Revolution of 1789 would ultimately achieve its fruition in the establishment of economic equality and social justice for the working classes. This humanitarian idea prompted Blum to many compromises in order to save rather than to destroy the precious heritage of French republican institutions. As the leader of the Socialist party from 1921 onward, Blum advocated responsible exercise of power rather than violent conquest of power. In 1936 he faced nationwide sitdown strikes as the first French Socialist prime minister. He was unable to prevent the steady drift of Europe toward war and the ignominious defeat of France in 1940. Through a judicious analysis of events the biographer demonstrates Blum's steadfast fidelity to the high ideals of humanism, social justice, republicanism and peace. Yet this does not completely vindicate or explain the unsuccessful policies of constant compromises, vacillations and ""appeasements"" characteristic of Blum and his contemporaries which failed to save France and the world from cataclysm. Copious documentation and reference to Blum's own writings and other substantial source material, a carefully ordered, expansive bibliography and other appendices form a work that is indispensable to an understanding of the French body politic under the Third Republic.