Many theists see moral positions as being defined by “God’s Law.” They argue for the objective existence of a morality revealed by ancient religious scriptures. However, they have the problem of how to select and interpret scriptures to find moral principles relevant to today’s world. Inevitably different interpretations abound
“What relevance does it have that people who profess to be Christians hold differing positions on various moral questions? Since the Bible holds a single position, and contradicts all others, these others are really irrelevant, even if people attempt to justify them using the Bible.”
The fallacy here, though, is that selection and interpretation is required to find this “single position.” This approach inevitably justifies moral positions by authority rather than reason. Anyone can claim their position is the authoritative one and all other interpretations wrong (sometimes even claiming personal communication with their god in justification).
No doubt the Westboro Baptist Church justifies their picketing of the Heath Ledger memorial this way (see also God Hates America and Fred Phelps). Argument for a moral position on the basis of biblical authority can be used to justify any position – from the most benign to the most hateful.
The scientific understanding of morality doesn’t claim an objective “god-give” morality but seeks to understand how humanity’s moral intuitions and todays moral positions evolved. Results indicate that rather than religion being a source of our morals it has become a way of codifying and justifying moral positions that have arisen quite independently.
Pascal Boyer summarises it this way in his excellent book Religion Explained: The Evolutionary Origins of Religious Thought.
Our evolution as a species of cooperators is sufficient to explain the actual psychology of moral reasoning, the way children and adults represent moral dimensions of action. But then this requires no special concept of religious agent, no special code, no models to follow. However, once you have concepts of supernatural agents with strategic information, these are made more salient and relevant by the fact that you can easily insert them in moral reasoning that would be there in any case. To some extent religious concepts are parasitic upon moral intuitions.
So, theists arrive at their moral positions the same way as anyone else. But some attempt to give their position authority by declaring existence of an objective, god-given morality that they have direct access to.
Some theists will reject this research. Their reactions are similar to the way that some reject modern evolutionary theory. They prefer to hold on to a story of “god-given” morality in much the same way as creationists prefer biblical or supernatural explanations of the origins of life and humanity. So, clearly the scientific investigation of morality is going to come under the same sorts of attacks as evolutionary theory currently experiences.
Steven Pinker’s article The Moral Instinct
Jonathan Haidt’s paper The New Synthesis in Moral Psychology
Jonathan Haidt’s Edge article Moral Psychology and the Misunderstanding of Religion.
Religious diversity includes “non-believers”
Common values, common action?
Is religion the source of morality?
Morals, values and the limits of science
Christian problems with morality