One can imagine a kind of hormonal arms race or genetic arms race, whether it's to do with height or IQ, conceivably, in the future. So it's limitless, and that's another of the features that sets it apart from medical intervention.

It's possible to make sense of what's morally at stake in an appreciation of the gift of life, or the gift of a child, without necessarily presupposing that there is a giver. What matters is that the gift - in this case, the child - not be wholly our own doing, our own product.

One of the ways in which parenting is a learning experience and an opportunity for moral growth is that we learn as parents that we don't choose the kind of child that we have.

Other animals can make sounds, and sounds can indicate pleasure and pain. But language, a distinctly human capacity, isn´t just for registering pleasure and pain. It´s about declaring what is just and what is unjust, and distinguishing right from wrong. We don´t grasp these things silently, and then put words to them; language is the medium through which we discern and deliberate about the good.

I think people who want to use genetic technologies to gain a competitive edge for their children are engaging in a kind of overreaching that could really undermine our appreciation of children as gifts for which we should be grateful and, instead, to view them as products or instruments that are there to be molded and directed.

My goal is first of all to promote a public debate about where markets serve the public good and where they don't belong. That's my first goal.

If we go too far down the road of choosing the genetic traits of children, my worry is that parenting will be less a kind of school for humility than it should be, and we will become too accustomed to regarding children as instruments of our ambition and of our desires.