This is a reproduction of one of P.J Proudhon's later works, Du Principe federatif, or The Principle of Federation. The translation of the text from French is by Dr Richard Vernon, a professor of Political Science at the University of Western Ontario. It is, in the humble opinion of this publisher, a true gem among the many works of Proudhon and a worthy addition to a rich history of writings in both the anarchist and federalist traditions.