What is the basis of morality? By what right can you expect anyone to follow moral rules, if there is no transcendent reality to ground them in?I have had a very engaging discussion of this (and related issues) with Ken Brown and other commenters on his blog, and have posted some of my own thoughts here. Ken and colleagues are coming specifically from a Christian perspective. (I have yet to see them give a satisfactory justification for how a "transcendent reality" solves the problem - but that's a topic for another time. As is the whole burden of actually demonstrating that such a reality exists - which would seem to be a prerequisite if one is to pin one's entire moral philosophy on it.)
I thought I might pick out the key points of my answer here.
First, I come back to a very pragmatic position: most of the key elements of morality (love, fairness, honesty, nonviolence, etc) are built into most humans. (This fact has very interesting naturalistic explanations in the context of evolution as a social species, but that too, is a topic for another time.) So we have a useful basis for discussing moral issues without either an esoteric knowledge of the philosophical underpinnings of morality or a belief in a transcendent basis for moral claims. This is the basis of secular government: we build our society on the foundations we all share.
Second and more important, how I can derive another's obligation from my "relativist" moral stance? Very cautiously and humbly. For most cases where someone says "there ought to be a law", there probably oughtn't. Law - the formal, coercive expression of our shared moral principles - is a blunt instrument that should not be used to solve all problems.
But even aside from the law, I do expect people to act morally, and I reserve the right to hold them accountable when they don't. How do I do this? What gives me, a relativist with no ultimate explanation for right and wrong, the right to project my moral judgments on others? Why should someone else do the right thing rather than some other thing? The most honest answer I can give is very simple:
People should do the right thing, because it's the right thing to do.I know that's not very philosophical or subtle. But, so long as we all share a basic sense of right and wrong, it's sufficient for the vast majority of life's decisions.
And for those issues where we don't instinctively agree on the right answer - abortion, euthanasia, drug control, etc - pretending that a hypothetical transcendent realm holds the answer does not seem to solve things. It may give some people a sense of self-righteousness to bolster their support of one position, but it is useless in seeking a practical solution or persuading people who believe in a different hypothetical set of transcendent moral truths (or folks like me who doubt such a set exists at all). In these cases, we have to fall back on the nasty, brutish, fallible strategy of using rhetoric and reason to pursue the best solution and persuade each other of it.
Justice statue on Old Bailey, London: from Wikipedia, shared by user Erasoft24 under Creative Commons Attribution licence 2.5.