Over at Open Culture:
Some of the most-referenced Western political thinkers—like Thomas Hobbes, John Locke, and Thomas Jefferson—have taken hierarchies of class, race, or both, for granted. Not so some of their more radical contemporaries, like Jean-Jacques Rousseau and Thomas Paine, who made forceful arguments against inequality. A strain of utopianism runs through more egalitarian positions, and a calculating pragmatism through more libertarian. Rarely have these two threads woven neatly together.
In the work of 20th century political philosopher John Rawls, they do, with maybe a knot or a kink here and there, in a unique philosophy first articulated in his 1971 book A Theory of Justice, a novel attempt at reconciling abstract principles of liberty and equality (recently turned into a musical.)