social contract 
(also social compact)
noun
An implicit agreement among the members of a society to cooperate for social benefits, for example by sacrificing some individual freedom for state protection. Theories of a social contract became popular in the 16th, 17th, and 18th centuries among theorists such as Thomas Hobbes, John Locke, and Jean-Jacques Rousseau, as a means of explaining the origin of government and the obligations of subjects.The rights we have are there by accord and by some kind of social contract - a social contract that is also to an extent built upon biology....
- As is true in society, an implicit social contract serves as the basis for maintaining order in schools.
- The social compact underpinning any society is that citizens are not permitted to kill or maim their fellows.