Answer: Social contract theory, nearly as old as philosophy itself, is the view that persons’ moral and/or political obligations are dependent upon a contract or agreement among them to form the society in which they live. Socrates uses something quite like a social contract argument to explain to Crito why he must remain in prison and accept the death penalty. However, social contract theory is rightly associated with modern moral and political theory and is given its first full exposition and defense by Thomas Hobbes.
(looked some of this up to help you a bit better :) )