How does John Rawls use hypothetical consent to explain justice and legitimacy?

In the philosophy of law and political theory, John Rawls utilizes the concept of hypothetical consent to establish the legitimacy of political principles and define justice as fairness.123

Rather than grounding legitimacy in actual, historical, or tacit consent, Rawls argues that the validity of social and political institutions rests on what rational agents would freely choose under specific, idealized conditions. To ensure fairness, he places these agents in an "original position" behind a "veil of ignorance." In this state, individuals are unaware of their own social class, race, sex, talents, or personal conceptions of the "good life".214

Rawls contends that because these individuals cannot act out of self-interest to favor their own specific group, they would rationally agree to two fundamental principles of justice:13
* Equal Liberty: Each person has an equal right to the most extensive basic liberties compatible with similar liberties for all.14
* Regulation of Inequalities: Social and economic inequalities are permissible only if they benefit the least-advantaged members of society and are attached to positions open to all under fair equality of opportunity.14

By demonstrating that these principles would be the object of universal agreement among rational, impartial parties, Rawls provides a framework for political legitimacy that transcends the limitations of actual consent.23