
He asked what principles of justice you would choose if you didn't know who you'd be. The answer was more radical than anyone expected.
Rawls spent twenty years writing A Theory of Justice, which appeared in 1971 and immediately became the most discussed work in political philosophy since Mill. Its central device was the veil of ignorance: imagine choosing the principles that will govern your society without knowing your position in it — your race, class, talent, or fortune. From behind this veil, Rawls argued, rational people would choose two principles: equal basic liberties for all, and economic inequalities allowed only when they benefit the least advantaged. The second principle was more demanding than it looked: it did not permit inequality for its own sake but only when it raised the floor. He revised and extended the argument for the rest of his life, making it less dependent on a particular account of rationality and more on the idea of a political consensus among people with fundamentally different views of the good life. He was quiet, methodical, and private. The argument did the work.

“Justice is the first virtue of social institutions, as truth is of systems of thought.”
“Each person possesses an inviolability founded on justice that even the welfare of society as a whole cannot override.”
Rawls completed his doctorate at Princeton in 1950. His dissertation on ethical judgments was the first sketch of what would become reflective equilibrium — the idea that we reach ethical principles by moving between our intuitions and our theories until they cohere. He spent the next two decades refining the approach.
Published in 1971, A Theory of Justice was immediately recognized as the most important work of political philosophy since Mill. It revived the social contract tradition, replaced the utilitarian consensus in academic philosophy, and gave a systematic basis for liberal egalitarianism. Rawls spent the rest of his career defending and revising it.
Nussbaum developed the capabilities approach partly as an answer to Rawls: his account of primary goods was too thin and too focused on resources, missing what people actually need to live fully human lives.
Appiah works within and extends the Rawlsian tradition of liberal political philosophy, bringing it into conversation with identity, multiculturalism, and the ethics of belonging across cultural difference.