Evidence that morality is all in the brain keeps rolling in. The Washington Post recently highlighted research from the National Institutes of Health that appeared to show that altruism feels good and is hard-wired into the brain. Jordan Grafman and his colleagues found that when volunteers placed the interests of others above their own, lights went on in a primitive part of the brain which usually responds to food or sex.

The neuroscientists who are working on experiments of this kind believe that morality and immorality can be reduced, broadly speaking, to brain chemistry rather than free will. "Eventually, you are bound to get into areas that for thousands of years we have preferred to keep mystical," says Dr Grafman. "Some of the questions that are important are not just of intellectual interest, but challenging and frightening to the ways we ground our lives. We need to step very carefully."

Harvard researcher Marc Hauser goes even further. He believes that morality is like language. People may be able to reach moral conclusions in the same way that they construct sentences, without having been trained in linguistics, because its foundations are basically neurological.