A state is a centralized political organization that imposes and enforces rules over a population within a territory. There is no undisputed definition of a state. One widely used definition comes from the German sociologist Max Weber: a "state" is a polity that maintains a monopoly on the legitimate use of violence, although other definitions are not uncommon. Absence of a state does not preclude the existence of a society, such as stateless societies like the Haudenosaunee Confederacy that "do not have either purely or even primarily political institutions or roles". The level of governance of a state, government being considered to form the fundamental apparatus of contemporary states, is used to determine whether it has failed. Most often, a country has a single state, with various administrative divisions. It is a unitary state or a federal union; in the latter type, the term "state" is sometimes used to refer to the federated polities that make up the federation. (Other terms that are used in such federal systems may include “province”, “region” or other terms.) Most of the human population has existed within a state system for millennia; however, for most of prehistory people lived in stateless societies. The earliest forms of states arose about 5,500 years ago as governments gained state capacity in conjunction with rapid growth of cities, invention of writing and codification of new forms of religion. Over time, a variety of forms of states developed, which used many different justifications for their existence (such as divine right, the theory of the social contract, etc.). Today, the modern nation state is the predominant form of state to which people are subject. Sovereign states have sovereignty; any ingroup's claim to have a state faces some practical limits via the degree to which other states recognize them as such.