I am trying to get at the moral arguments and the ethical status of various attempts at enhancement, or genetic engineering, or the bid for designer children. But there are implications for society at large.

A better way to mutual respect is to engage directly with the moral convictions citizens bring to public life, rather than to require that people leave their deepest moral convictions outside politics before they enter.

Parental love is not contingent on the talents and attributes the child happens to have. We choose our friends and spouses at least partly on the basis of qualities we find attractive. But we do not choose our children. Their qualities are unpredictable, and even the most conscientious parents cannot be held wholly responsible for the kind of child they have. That is why parenthood, more than other human relationships, teaches what the theologian William F. May calls an “openness to the unbidden.

They say the state should not impose on its citizens a preferred way of life, but should leave them as free as possible to choose their own values and ends, consistent with a similar liberty for others.

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.

It is true that the Jewish tradition emphasizes the moral mandate to save life. It also has a different position from the Catholic Church on the moral status of the embryo. It has a more developmental view of when human life, in the sense of personhood, begins than does the Catholic Church.

Whether you're a libertarian liberal or a more egalitarian liberal, the idea is that justice means being non-judgmental with respect to the preferences people bring to public life.