Many commentators have failed to identify the important issues at the heart of the debate between Habermas and Rawls. This is partly because they give undue attention to differences between their respective devices of representation, the original position and principle (U), neither of which are germane to the actual dispute. The dispute is at bottom about how best to conceive of democratic legitimacy. Rawls indicates where the dividing issues lie when he objects that Habermas’s account of democratic legitimacy is comprehensive and his is confined to the political. But his argument is vitiated by a threefold ambiguity in what he means by “comprehensive doctrine.” Tidying up this ambiguity helps reveal that the dispute turns on the way in whi...