 When people mutually covenant each to the others to obey a common authority, they have established what Hobbes calls “sovereignty by institution”. When, threatened by a conqueror, they covenant for protection by promising obedience, they have established “sovereignty by acquisition”. These are equally legitimate ways of establishing sovereignty, according to Hobbes, and their underlying motivation is the same—namely fear—whether of one’s fellows or of a conqueror. The social covenant involves both the renunciation or transfer of right and the authorization of the sovereign power. Political legitimacy depends not on how a government came to power, but only on whether it can effectively protect those who have consented to obey it; political obligation ends when protection ceases.