The final disquiet, I think, that is elicited by the naturalist or biological approach to the mind, is that it robs us of responsibility. If we act only because of ricocheting molecules in the brain, shaped by the genes which in turn were shaped by natural selection -- if it's billiard balls all the way down and all the way back -- then how can we hold someone responsible for his actions, given that there is no "he" that caused them? I agree this is a fascinating puzzle, but I don't think it has anything particular to do with cognitive neuroscience or behavioral genetics or evolutionary psychology. It's a problem that is raised by any attempt to explain behavior, regardless of the nature of the explanation. You all remember the scene in "West Side Story" in which the gang of juvenile delinquents explains to Sergeant Krupke, "We're depraved on account of we're deprived":

"Dear kindly Sergeant Krupke, You gotta understand, It's just our bringing up-ke, That gets us out of hand. Our mothers all are junkies, Our fathers all are drunks. Golly Moses, naturally we're punks!"

Sondheim's lyrics send up the psychoanalytic and social-science exculpations of bad behavior that were popular in the 1950s, and the non-biological excuses continue. In the 1970s, Dan White was given a light sentence for murdering the mayor of San Francisco because his mind was addled from too much junk food, the infamous Twinkie Defense. In the 1990s, the lawyer for the Menendez brothers argued her way to an acquittal based on her client's diminished responsibility because of childhood sexual abuse. Any time someone explains behavior, biologically or otherwise, a thoughtless observer can imagine that the explanation absolves the actor of responsibility. According to an old saying, to understand is not to forgive. If a moral system locates responsibility in a ghost in the machine, we need to revise the moral system, because the ghost is being exorcised, but we still need the notion of individual responsibility. Any ethical theory that is challenged by some outcome from the laboratory is a defective, or at least an incomplete, ethical theory.

Yesterday I was on the radio with a professor of divinity who said it was crucial that we retain the idea of a unified self, a part of the brain where it all comes together -- the ethical system of two billion people depends on it, he said. I replied there's considerable evidence that the unified self is a fiction -- that the mind is a congeries of parts operating asynchronously, and that it's only an illusion that there's a president in the Oval Office of the brain who oversees the activity of everything. He said, "I hope that's not true, because if it is we'll have to change our ethical system." I think this is an unwise way of doing moral reasoning. He might be right; I suspect that he's wrong; but whether he's right or wrong, we don't want the morality of killing and raping and lying and stealing to depend on what comes out of the psychology lab down the hall. We need our ethical system to be more robust than that -- it's always wrong to kill people, and we need an ethical system for which that's axiomatic.

To conclude -- we look with wry amusement at the debates in cosmology of three or four hundred years ago, in which great moral significance was attached to the debate between the geocentric and heliocentric theories. It was considered not to be just an empirical question of science, but a problem of great moral weight whether the earth went around the sun or the sun went around the earth. Now we look back and see that this was all rather silly. Either one theory is true or the other one is true, and people had to find out which is which. Any notion that meaning, purpose, ethics, morals and so on hinge on that contingent fact of cosmology came from unsound reasoning. I suspect that the idea that meaning, purpose, and morals hinge on a Soul one, a ghost in the machine, will have the same fate. The ghost in the machine has been exorcised, and meaning and values are none the worse for it. Thank you very much.