"Property is theft!" is a slogan coined by Pierre-Joseph Proudhon in "What is Property?" By "property", Proudhon referred to a concept regarding land property that originated in Roman law. Proudhon's concept of "property" was criticized by Karl Marx who wrote that the expression "property is theft" is self-refuting and unnecessarily confusing, stating that "'theft' as a forcible violation of property presupposes the existence of property" and condemning Proudhon for entangling himself in "all sorts of fantasies, obscure even to himself, about true bourgeois property".