Friedrich Nietzsche's descent into madness prevented him from achieving his dream of seeing Paris, but his philosophical alter-ego Zarathustra took the City of Light by storm, raising sharp debates among the political and cultural avant-garde about the very foundations of modern philosophy, social thought and political life. This intellectual history reveals Nietzsche's impact upon the French life of the mind and clarifies the crisis in European thought that foreshadowed and helped bring about World War I. The author examines a broad range of intellectuals and opinion-makers, including artists, politicians, academics and journalists, demonstrating that social frameworks such as institutional affiliation, aesthetic allegiance and generational identity, even more than class or political sympathies, shaped responses to Nietzsche's writings. This discovery allows the author to broaden his inquiry into a general sociology of knowledge that explores the several ways a thinker becomes recognized as important by cultural and political leaders. In addition, he reveals the subtle linkages between the reception of Nietzsche and the shifting currents of social and political developments leading to World War I. In 1900 many represented Nietzsche as a "good European" who transcended national divisions, but by 1914 patriotic fervour led many French critics to repudiate Nietzsche and his disciples. During the Great War most intellectuals turned against Nietzsche, with Leon Daudet blaming him for laying the philosophical groundwork for German barbarities in Belgium and occupied France. Opening new avenues for understanding French and European intellectual life in the era before the Great War, this study should be useful to historians, political scientists, philosophers and sociologists, and anyone interested in the cultural politics and literary and political avant-garde of the early 20th century.