Somewhat like Darwinism, neuroscience is a field which is being mined for all the answers to all the questions about what it means to be human. A plethora of new books and articles claims that morality is biologically based. One was reviewed recently in Science, "The Neuroscience of Fair Play: Why We (Usually) Follow the Golden Rule", by Donald W. Pfaff. The author aims to present a possible neural and genetic basis for the Golden Rule, not very successfully, according to the reviewer.

The latest convert is British philosopher A.C. Grayling. He writes in the New Scientist that the existence of mirror neurons proves that moral relativism is wrong. These are cells which fire when we perceive the actions of others-- smiling, yawning, weeping and so on. "This means that the ultimate basis for moral judgement is hard-wired, and therefore universal. So even when customs differ, fundamental morality does not," he says.

The existence of an objective morality has fewer and fewer defenders nowadays, but its champions may not wish to enlist Professor Grayling. A significant problem with his theory is that mirror neurons may not exist. They have been observed in macaque monkeys, but not in humans. It seems a bit early to close the file on moral relativism, on the basis of conflicting and tentative experimental results in a different species. ~ Science, May 2; New Scientist, May 3