"Rawls’ account of the public use of reason allows for religiously motivated arguments, but not for the appeal to “comprehensive” religious doctrines for justification. Justification must rely solely on “proper political reasons” (which means mainly reasons that are available to everyone regardless of the specific commitments they may have to religion or substantive conceptions of the good or their embeddedness in cultural traditions). This is, as Habermas indicates, an importantly restrictive account of the legitimate public use of reason – one which will strike many as not truly admitting religion into public discourse. Crucially, Habermas follows Wolterstorff in arguing that it is in the nature of religion that serious belief is understood as informing – and rightly informing – all of a believer’s life. This makes sorting out the “properly political” from other reasons both practically impossible in many cases and an illegitimate demand for secularists to impose. Attempting to enforce it would amount to discriminating against those for whom religion is not “something other than their social and political existence”. On more ambiguous grounds, Habermas does hold it acceptable to demand “properly political” justifications, independent of religion, from politicians even if not from those who vote for or endorse them.
Habermas seeks to defend a less narrow liberalism, one that admits religion more fully into public discourse (including both democratic will formation and the rule of law) but seeks to maintain a secular conception of the state. He understands this as requiring impartiality in state relations to those of any religious orientation or none and to all religious communities, but not as requiring the stronger laïc prohibition on state action affecting religion even if impartially. Indeed, he goes so far as to suggest that the liberal state and its advocates are not merely enjoined to religious tolerance but – at least potentially – cognizant of a functional interest in public expressions of religion. These may be key resources for the creation of meaning and identity; secular citizens can learn from religious contributions to public discourse (not least when these help clarify intuitions the secular have not made explicit)."