In 1971 John Rawls published A Theory of Justice; over time, he appears to have become dissatisfied with the shape his theory had originally taken. The problem, Rawls says, is that he had initially assumed that the two principles of justice as fairness (the principle of equal basic rights and liberties and the principle of fair equality of opportunity paired with mutual benefit in outcomes and, in the ideal case, the greatest benefit of the least well-off income group) would become part of an overarching moral theory in any well-ordered society in which these principles were the public principles of justice. Such a society would be stable because everybody in it would continue to hold to the two principles in the light of this overarching moral theory, which contained those principles as an integral part. But such uniform acceptance of a moral theory, Rawls now says, is implausible. (For Rawls’s own account of the problem, see PL xv–xviii; also CP 414 n.33.)

In Rawls’s writings in the 1980s, he argues that there is going to be, in a continuing free and open society, an irreducible pluralism of reasonable comprehensive moral and religious and philosophical doctrines. Accordingly, a new idea, overlapping consensus, is called on to form the basis of stability in a well-ordered, pluralistic society. An overlapping consensus is said to hold in a society when individuals who adhere to different comprehensive doctrines can nonetheless agree on a political conception of justice for evaluating the shared basic institutional structure of their society.