In political science, legitimacy is the right and authority to governed  authority, usually a governing law or a régime. Whereas "authority" denotes a specific position in an established government, the term "legitimacy" denotes a system of government — wherein "government" denotes "sphere of influence". Political legitimacy is considered a basic condition for governing, without which a government will suffer legislative deadlock(s) and collapse. In political systems where this is not the case, unpopular régimes survive because they are considered legitimate by a small, influential élite. In Chinese political philosophy, since the historical period of the Zhou Dynasty (1046–256 BC), the political legitimacy of a ruler and government was derived from the Mandate of Heaven, and unjust rulers who lost said mandate therefore lost the right to rule the people.