Paul Weithman, Why Political Liberalism?: On John Rawls's Political Turn (Oxford, UK: Oxford University Press, 2011).

From the publisher:

In Why Political Liberalism? , Paul Weithman offers a fresh, rigorous, and compelling interpretation of John Rawls’s reasons for taking his so-called “political turn”. Weithman takes Rawls at his word that justice as fairness was recast as a form of political liberalism because of an inconsistency Rawls found in his early treatment of social stability. He argues that the inconsistency is best seen by identifying the threats to stability with which the early Rawls was concerned. One of those threats, often overlooked by Rawls’s readers, is the threat that the justice of a well-ordered society would be undermined by a generalized prisoner’s dilemma. Showing how the Rawls of “A Theory of Justice” tried to avert that threat shows that the much-neglected third part of that book is of considerably greater philosophical interest, and has considerably more unity of focus, than is generally appreciated.

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