Pierre-Joseph Proudhon (1809-1865) was one of Europe's most well-known socialists during his lifetime. His complete works span over sixty volumes. From his opening salvo on the social origins of the Sabbath, to the claim that "all property is theft!," to his final writings on international relations, federalism, and the political capacity of the working class, his works shaped European socialism for a generation, and continue to act as the intellectual spine of modern anarchism.