Sociological analysis of the role of punishment in modern society started with the same issue as that of the Utilitarian philosophers mentioned in the previous section. As feudal, land-based societies changed into industrial, urbanized modern society, and as autocratic kings gave way to consti-tutional monarchies or republics, criminal law and punishment became encompassed by the general question of what should be the role and limits of the power of government. The principal idea to emerge was social con¬tract theory, according to which the existence of 'society', as opposed to a group of mutually predatory individuals, depends on the existence of a contract (tacit, unwritten) between citizens and government, such that some degree of individual freedom is surrendered in return for government protection against harm from others. There are variants in the social con¬tract theories that developed in the seventeenth and eighteenth centuries, but all incorporate this essential idea. The best-known British versions of social contract theory are those of Hobbes (1962), who in his book Leviathan argued that mutual obligation did not exist prior to the consti¬tution of a sovereign state, and that rebellion against the state cannot be justified, and Locke (1924), who argued that principles of morality and mutual obligation can be derived from nature and thus exist prior to the formation of states, and states can therefore be challenged or overthrown if they fail to uphold these principles. Another well-known version of social contract theory is that of Rousseau (1973). 'Man is born free but is every¬where in chains' is probably one of the most-quoted phrases from modern philosophy. In fact, it is not a call to rebellion, but an observation, and in his book on the social contract he asks why, under what conditions, people are willing to surrender their freedom to governments.