This document summarizes and compares the Utopian social theories of Saint-Simon, Fourier, Owen, and Proudhon. Saint-Simon proposed a harmonious society led by scientists and administrators where the state would gradually become unnecessary. Fourier envisioned communities organized around human passions. Owen established self-sustaining communities for workers but his New Harmony experiment failed. Proudhon was a critic of previous Utopians and advocated for economic reforms. The document asserts that the Saint-Simonian model, which emphasized large-scale scientific planning, was the most practical of the Utopian plans.