Discipline: Political Science
Argument of French anarchist Pierre-Joseph Proudhon (1809-1865).
In translation the claim is self-contradictory, since without the concept of property 'theft' is meaningless.
What Proudhon meant was that purely legal ownership without any of the responsibilities which went with it was a theft from those who actually worked the land, or the raw materials, from which the owners profited.
Source:
George Woodcock, Anarchism (Harmondsworth, 1963)