The fundamental work "History of Socialism" was written mainly by K. Kautsky, but some chapters included in the second part of the publication belong to his co-authors P. Lafargue, E. Bernstein and K. Hugo. The book examines the economic, social and ideological foundations of various egalitarian theories, their development in history and consistent change. Being associated with the development of Russian society and certain areas in its ideology, the publication has historical significance.