The alleged incompleteness of public reason

According to John Rawls's ideal of liberal public reason, comprehensive moral, religious and philosophical doctrines should play no more than an auxiliary or marginal role in the political life of constitutional democracies. David Reidy has recently claimed that since liberal public reason is incomplete, comprehensive doctrines, and non-public reasons, must play a wider role than Rawls admits. In response, I argue that Reidy's arguments do not establish that liberal public reason is incomplete. Furthermore, even if the substantive values embodied in liberal public reason were insufficient to determine certain fundamental decisions, such indeterminacy need not be eliminated by recourse to comprehensive doctrines.