a basic feature of democracy is the fact of reasonable pluralism-the fact that a plurality of conflicting reasonable comprehensive doctrines, religious, philosophical, and moral, is the normal result of its culture of free institutions.  Citizens realize that they cannot reach agreement or even approach mutual understanding on the basis of their irreconcilable comprehensive doctrines. In view of this, they need to consider what kinds of reasons they may reasonably give one another when fundamental political questions are at stake. I propose that in public reason comprehensive doctrines of truth or right be replaced by an idea of the politically reasonable addressed to citizens as citizens.
--John Rawls, "The Idea of Public Reason Revisited," Chicago Law Review (1997), 64 (3): 765-807.