John Bordley Rawls (; February 21, 1921 - November 24, 2002) was an American moral and political philosopher in the liberal tradition. He held the James Bryant Conant University Professorship at Harvard University and the Fulbright Fellowship at the University of Oxford. Rawls received both the Schock Prize for Logic and Philosophy and the National Humanities Medal in 1999, the latter presented by President Bill Clinton, in recognition of how Rawls's work "helped a whole generation of learned Americans revive their faith in democracy itself." In his 1990 introduction to the field, Will Kymlicka wrote that "it is generally accepted that the recent rebirth of normative political philosophy began with the publication of John Rawls's A Theory of Justice in 1971."

Rawls derives two principles of justice from the original position. The first of these is the Liberty Principle, which establishes equal basic liberties for all citizens. 'Basic' liberty entails the (familiar in the liberal tradition) freedoms of conscience, association and expression as well as democratic rights; Rawls also includes a personal property right, but this is defended in terms of moral capacities and self-respect, rather than an appeal to a natural right of self-ownership (this distinguishes Rawls's account from the classical liberalism of John Locke and the libertarianism of Robert Nozick).  Rawls argues that a second principle of equality would be agreed upon to guarantee liberties that represent meaningful options for all in society and ensure distributive justice. For example, formal guarantees of political voice and freedom of assembly are of little real worth to the desperately poor and marginalized in society. Demanding that everyone have exactly the same effective opportunities in life would almost certainly offend the very liberties that are supposedly being equalized. Nonetheless, we would want to ensure at least the "fair worth" of our liberties: wherever one ends up in society, one wants life to be worth living, with enough effective freedom to pursue personal goals. Thus participants would be moved to affirm a two-part second principle comprising Fair Equality of Opportunity and the famous (and controversial) difference principle. This second principle ensures that those with comparable talents and motivation face roughly similar life chances and that inequalities in society work to the benefit of the least advantaged.  Rawls held that these principles of justice apply to the "basic structure" of fundamental social institutions (such as the judiciary, the economic structure and the political constitution), a qualification that has been the source of some controversy and constructive debate (see the work of Gerald Cohen).  Rawls further argued that these principles were to be 'lexically ordered' to award priority to basic liberties over the more equality-oriented demands of the second principle. This has also been a topic of much debate among moral and political philosophers.  Finally, Rawls took his approach as applying in the first instance to what he called a "well-ordered society ... designed to advance the good of its members and effectively regulated by a public conception of justice". In this respect, he understood justice as fairness as a contribution to "ideal theory", the determination of "principles that characterize a well-ordered society under favorable circumstances". Much recent work in political philosophy has asked what justice as fairness might dictate (or indeed, whether it is very useful at all) for problems of "partial compliance" under "nonideal theory".

What is the difference principle?
those with comparable talents and motivation face roughly similar life chances and that inequalities in society work to the benefit of the least advantaged.