From The New York Times:
In a series of recent articles and a book, “The Happiness Hypothesis,” Jonathan Haidt, a moral psychologist, has been constructing a broad evolutionary view of morality that traces its connections both to religion and to politics. Dr. Haidt (pronounced height) began his research career by probing the emotion of disgust. Testing people’s reactions to situations like that of a hungry family that cooked and ate its pet dog after it had become roadkill, he explored the phenomenon of moral dumbfounding — when people feel strongly that something is wrong but cannot explain why.
Dumbfounding led him to view morality as driven by two separate mental systems, one ancient and one modern, though the mind is scarcely aware of the difference. The ancient system, which he calls moral intuition, is based on the emotion-laden moral behaviors that evolved before the development of language. The modern system — he calls it moral judgment — came after language, when people became able to articulate why something was right or wrong.
Moral dumbfounding, in Dr. Haidt’s view, occurs when moral judgment fails to come up with a convincing explanation for what moral intuition has decided. So why has evolution equipped the brain with two moral systems when just one might seem plenty?