The purpose of this article is to understand Vilfredo Pareto’s reading of the Saint-Simonian system, namely the project of a new social order based on an industrial organisation. Why did Pareto rank this system among modern socialist systems and why did he qualify it as a pseudo-scientific system and nothing more than a religious system? The reason why he perceived Saint-Simonianism as a non-science can be inferred from both pure theory of political economy and the theory of social evolution. The identification of Saint-Simonianism with a religious system probably derives from the first historians and commentators of socialism in the mid-nineteenth century.