Anarchy is a form of society without rulers. It is primarily advocated by anarchists who propose replacing the state with a stateless society based on voluntary free association. These institutions or free associations are generally modeled to represent concepts such as community and economic self-reliance, interdependence, or individualism. In simple terms anarchy means 'without rulers' or 'without authority'. As such, under anarchy there is no coercive rule by a single group or individual, rather instead by an individual upon themselves or by the people entirely. 
 As a concept, anarchy is commonly defined by what it excludes. Etymologically, anarchy is derived from the Greek: αναρχία, romanized: anarkhia; where "αν" ("an") means "without" and "αρχία" ("arkhia") means "ruler". Therefore, anarchy is fundamentally defined by the absence of rulers.
 While anarchy specifically represents a society without rulers, it can more generally refer to a stateless society, or a society without government. Anarchy is thus defined in direct contrast to the State, an institution that claims a monopoly on violence over a given territory. Anarchists such as Errico Malatesta have also defined anarchy more precisely as a society without authority, or hierarchy.
 Anarchy is also often defined synonymously as chaos or social disorder, reflecting the state of nature as depicted by Thomas Hobbes. By this definition, anarchy represents not only an absence of government but also an absence of governance. This connection of anarchy with chaos usually assumes that, without government, no means of governance exist and thus that disorder is an unavoidable outcome of anarchy. Sociologist Francis Dupuis-Déri has described chaos as a "degenerate form of anarchy", in which there is an absence, not just of rulers, but of any kind of political organization. He contrasts the "rule of all" under anarchy with the "rule of none" under chaos.
 Since its conception, anarchy has been used in both a positive and negative sense, respectively describing a free society without coercion or a state of chaos.
 Peter Leeson examined a variety of institutions of private law enforcement developed in anarchic situations by eighteenth century pirates, preliterate tribesmen, and Californian prison gangs. These groups all adapted different methods of private law enforcement to meet their specific needs and the particulars of their anarchic situation.
 In international relations, anarchy is "the absence of any authority superior to nation-states and capable of arbitrating their disputes and enforcing international law".
 As a political philosophy, anarchism 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 opposition to the state is central, it is a necessary but not sufficient condition. Anarchism also entails opposing unnecessary authority or hierarchical organisation in the conduct of all human relations, including yet not limited to the state system.
 The German philosopher Immanuel Kant treated anarchy in his Anthropology from a Pragmatic Point of View as consisting of "Law and Freedom without Force". For Kant, anarchy falls short of being a true civil state because the law is only an "empty recommendation" if force is not included to make this law efficacious. For there to be such a state, force must be included while law and freedom are maintained, a state which Kant calls a republic. Kant identified four kinds of government: