Those who argue that bioengineering is similar in spirit to other ways ambitious parents shape and mold their children have a point. But this similarity does not give us reason to embrace the genetic manipulation of children. Instead, it gives us reason to question the low-tech, high-pressure child-rearing practices we commonly accept.

The problem lies in the hubris of the designing parents, in their drive to master the mystery of birth. Even if this disposition does not make parents tyrants to their children, it disfigures the relation between parent and child, and deprives the parent of the humility and enlarged human sympathies that an openness to the unbidden can cultivate.

When science moves faster than moral understanding, as it does today, men and women struggle to articulate their unease. In liberal societies, they reach first for the language of autonomy, fairness, and individual rights. But this part of our moral vocabulary does not equip us to address the hardest questions posed by cloning, designer children, and genetic engineering.