Religion, Morality, and Metaphysics — Here's a great quote from David Gauthier (twice as good as Rawls, but an 1/8 as famous!) pertaining to the post below:
Religious practice and religious language are, or until recently have been, ubiquitous in human life. But if we take religion at face value, and ask ourselves what must be the case if the claims of religion, literally construed so that they possess ordinary truth-value, are some of them to be true, then we find ourselves driven into an account of the world that is prodigal in admitting into its ontology entitites that play no role in our best explanations and justifications. … The only theory of religion that, to my mind, has the least credibility, is an error theory. [I am not the least easy about this, but] I should be even more uneasy were I to suppose that morality would share the fate of religion, so that our moral claims, literally construed, would, to be true, require us to accept a prodigal and ultimately incredible ontology.
Putting metaphysics first means building a moral theory that does its job with the materials actually provided by nature, and not with “exalted entitites,” to use Rawls's phrase.