The difference principle is perhaps the best-known and most controversial element of Rawls’s two principles of justice. It states that “social and economic inequalities are to be arranged so that they are . . . to the greatest beneit of the least advantaged” (TJ 266). As part of the two principles of justice, it has the lowest priority, which means that it cannot be satisied at the expense of the equal provision of basic liberties, fair equality of opportunity or the just savings principle. It holds that if a society provides for the satisfaction of these other aspects of the two principles equally, and its institutions and the various regulatory procedures they establish yield, when followed, a class of people who have fewer primary goods than anyone else in their society (the worst off) but who have more primary goods than the worst off in all other comparable societies with different basic structures, then that society is, for this reason, just.

As with other well-known parts of Rawls’s theory, such as the original position and the veil of ignorance, the difference principle is the subject of a voluminous secondary literature. Unfortunately, as with these other aspects of Rawls’s theory, much of that literature takes the difference principle out of the context of the full theory or treats it as if it is the whole of Rawls’s theory of justice (thus described as maximin justice). It is, for instance, important to an understanding of the difference principle that it applies only to the basic structure of a society as a whole, and that it serves to distinguish between the justice of institutional structures understood not as allocative schemes but as instances of what Rawls calls pure procedural justice. This entry places the difference principle within the context of the wider theory, explaining the role it plays there and the grounds for it within the larger theory. It then explains how the principle is to be applied.