I've often made the argument in these pages that moral judgments are vacuous unless there's an objective standard of moral goodness that transcends human feelings or subjectivity. I've also argued that the only such standard that can qualify is God, so that if God does not exist there really is no basis for moral judgment and no obligation to live one way rather than another.
But, why must the objective standard be God? Why can there not be a standard that transcends human subjectivity but also be something like Plato's ideal form of the good?
Plato (c. 427-c.347 B.C.), you might recall, believed that there existed in some ethereal realm the ideal (or form) of the Good, the Beautiful, and the True and everything that existed, to the extent that it contained some goodness, beauty, or truth did so because it derived these qualities from these ideals or forms. But ideal goodness cannot serve as the basis for moral obligation because a) it's not personal and b) it's unable to hold us accountable.
How, for example, can an impersonal standard of behavior communicate to us how we should act and how can it obligate us to act that way? And how can an impersonal abstraction hold us accountable for how we live?
The only adequate foundation for meaningful moral behavior is a transcendent, personal moral authority who is perfectly good and thus able to serve as a universal standard of goodness, and who has somehow intentionally instilled that standard in us and is powerful enough to hold us accountable for our fidelity to it.
This is very close to saying that in order for there to be objective moral duties there must be a God who grounds them.
So, if one refuses to accept that God exists several things follow:
1. Their moral judgments - whether about racism, sexual abuse, child abuse, torture, war and peace, whatever - are moral nullities. They're simply expressions of the speaker's personal predilections or tastes, and are of no more significance than their expressed preference for Coke rather than Pepsi. Individuals may adopt any attitude toward any of these behaviors they wish. They can choose to be kind, respectful, gentle and honest, but these are just individual preferences. Had they chosen to be the opposite they wouldn't be wrong in any moral sense, they'd just be different.
2. Anyone who asserts that racism, torture and the rest are objectively wrong but who denies there's an objective standard of right and wrong is sailing on a sea of incoherence.
3. The only rational position for such a person to hold regarding morality is moral nihilism - the denial of any objective moral duties altogether.
Of course, most people find moral nihilism repugnant, but it's the inevitable endpoint of any worldview that denies a personal, good, and very powerful God to whom we are morally accountable.