'The letters of Proudhon, even outside the circle of his particular friends, will always be of value; we can always learn something from them, and here is the proper place to determine the general character of his correspondence.'It has always been large, especially since he became so celebrated; and, to tell the truth, I am persuaded that, in the future, the correspondence of Proudhon will be his principal, vital work, and that most of his books will be only accessory to and corroborative of this. At any rate, his books can be well understood only by the aid of his letters and the continual explanations which he makes to those who consult him in their doubt, and request him to define more clearly his position.

Pierre-Joseph Proudhon (15 January 1809 19 January 1865) was a French socialist, politician, philosopher, economist and the founder of mutualist philosophy. He was the first person to declare himself an anarchist, using that term and is widely regarded as one of anarchism's most influential theorists. Proudhon is considered by many to be the 'father of anarchism'. Proudhon became a member of the French Parliament after the Revolution of 1848, whereafter he referred to himself as a federalist. Proudhon described the liberty he pursued as 'the synthesis of communism and property'. Some consider his mutualism to be part of individualist anarchism while others regard it to be part of social anarchism.