There is much that I can dispute in Andrew Ferguson's intelligent criticsm of my book (How the Mind Works) and article ("Why They Kill Their Newborns"). But I will address only his main accusation: that the search for a scientific explanation of the mind undermines morality and leaves me "close enough" to advocating the decriminalization of neonaticide. (As he points out, my stated position is that neonaticide is "an immoral act" and should not be decriminalized.)

Ferguson is right that I find myself in a "pickle" in failing to find boundaries of personhood in biology. But he missed the whole point of my discussion: everyone is in that pickle. If you believe the right to life inheres in being sentient, you must conclude that a hamburger-eater is a party to murder. If you believe it inheres in being a member of Homo sapiens, your are just a species bigot. If you think it begins with conception, you should prosecute IUD users for murder and divert medical research from preventing cancer and heart disease to preventing the spontaneous miscarriages of vast numbers of microscopic conceptuses. If you think it begins at birth, you should allow abortion minutes before birth, despite the lack of any significant difference between a late-term fetus and a neonate.

Biology does not announce solutions to our moral problems. My view is that we need to work them out by moral reasoning, using concepts such as right and wrong, free will, responsibility, interests, and rights, concepts that are not part of science. Ferguson worries that this makes them "pretenses," "a rickety platform from which to launch the pursuit of right and wrong." But in mathematics we reason with entities that are not part of science, such as perfect circles, infinite lines, and dimensionless points. There is nothing rickety about mathematical reasoning, and there need be nothing rickety about moral reasoning just because it depends on concepts that are not reducible to biology.

In place of moral reasoning, Ferguson seems to suggest that moral issues be resolved by appeals to religion. His argument against neonaticide is that "it has been viewed with abhorrence by Christians from the beginning of their era" because they believed that "human beings were persons from the start, endowed with a soul, created by God, and infinitely precious." But Ferguson evades the obvious problems in solving moral dilemmas by asking religious people what they do and don't abhor. That solution has given us stonings, witch-burnings, crusades, inquisitions, jihads, fatwas, suicide bombers, abortion-clinic gunmen, and mothers who drown their sons so they can be happily reunited in heaven.

It is Ferguson's mentality, not mine, that threatens the foundations of morality. Secular thinkers are prepared to struggle with difficult moral questions by reasoning them out on moral grounds, while welcoming our increasing knowledge about the brain. Ferguson instead seems to want to root morality on the theory that a deity injects a fertilized ovum with a ghostly substance, which registers the world, pulls the levers of behavior, and leaks out at the moment of death. Unfortunately for that theory, brain science has shown that the mind is what the brain does. The supposedly immaterial soul can be bisected with a knife, altered by chemicals, turned on or off by electricity, and extinguished by a sharp blow or a lack of oxygen. Centuries ago it was unwise to ground morality on the dogma that the earth sat at the center of the universe. It is just as unwise today to ground it on dogmas about souls endowed by God.