The approach of social contract is another important approach which should be regarded for normative thought. According to Locke and Rousseau, by forming a higher authority, individuals would accept voluntarily to leave their certain rights to preserve their freedoms and security (freedom of life). Social contract theory depends on the assumption that the individuals might voluntarily bind themselves to the certain principles. From this point, like stag hunt model of game theory, individuals would sacrifice their small satisfactions to reach a highest satisfaction.