A central idea of John Rawls's

theory of justice, referred to as the difference principle,

is that inequalities in the distribution of relevant goods are just if and only if these inequalities are needed to improve the plight of everyone, in particular of those who are the worst off.(See Rawls's second principle of justice, "A

Theory of Justice," p. 578, and G. A. Cohen's formulation,

"Where the Action Is," p. 599.)