A form of authority. Its principal characteristic is that it is the supreme or final authority, meaning that there is no other form of authority surpassing it. Sovereignty has taken a number of different forms throughout history, ranging from the tribal chief to feudal king and democratically elected president. The key political and theoretical problem it raises is the question of legitimacy: sovereignty is never purely intrinsic, or naturally occurring, it must be embedded in a social structure that serves as its condition of possibility. For instance, feudal kings ruled by virtue of their lineage and divine right. Ultimately, sovereignty can be seen as an issue of who has the right to rule and how that right is vested.