Anarchy is the condition of a society, entity, group of people, or a single person that rejects hierarchy. The word originally meant leaderlessness, but in 1840 Pierre-Joseph Proudhon adopted the term in his treatise What Is Property? to refer to a new political philosophy: anarchism, which advocates stateless societies based on voluntary associations. In practical terms, anarchy can refer to the curtailment or abolition of traditional forms of government and institutions. It can also designate a nation (or anywhere on earth that is inhabited) that has no system of government or central rule. Anarchy is primarily advocated by anarchists, individuals who propose replacing government with voluntary institutions.
Anarchism as a political philosophy advocates self-governed societies based on voluntary institutions. These are often described as stateless societies, although several authors have defined them more specifically as institutions based on non-hierarchical free associations. Anarchism holds the state to be undesirable, unnecessary, or harmful. While anti-statism is central, anarchism entails opposing authority or hierarchical organisation in the conduct of all human relations, including, but not limited to, the state system.