Recently, after a monkey named ANDi was born carrying jellyfish genes, George Will predicted that genetic engineering would "end the human story" in a manner more swift and certain than nuclear war. Will's fear was not that genetic monsters or superviruses would destroy us, but that the genetic design of humans--the choice, before conception, to give a child certain traits--would eliminate our respect for human life. Will's concern, and that of many who agree with him, is not only that the consequences of genetic engineering may be harmful, but that the practice itself is a moral evil. The question that must be asked in response is: Why?

The first consideration is whether, even if we agreed on a good thing genetic engineering could accomplish (say, preventing cystic fibrosis), it would still be wrong in all cases to use it. Unless there's something purposeful about the particular assortment of genes we're born with, there seems no reason not to change them. We interfere with natural biological processes every time we take an antibiotic, and only a very few religious sects maintain that curing disease goes against the rightful order of the world. To prohibit genetic engineering but not any other intervention in our biology seems no less arbitrary than simply declaring, "Genetic engineering is wrong."

Rather than condemn the process per se, most of those who oppose genetic engineering do so with an eye to the modifications it allows. Preventing diseases is one thing, but the same procedure can also be used to prevent any condition the parents find inconvenient. Assuming such traits are controlled by genes, would it be acceptable to prevent manic depression, or even (to shy away from controversy) homosexuality? If we endorse genetic engineering, would we have to accept a world where children are made to order, with good looks, smarts and Aryan features to boot?

Some have responded to this question by citing a child's right to an "open future," a right that is frustrated once parents exercise genetic control. To have their health, looks and perhaps even personalities decided before birth supposedly reduces our children's freedom--it violates their identity, changing what our children truly are. But to speak of genetic engineering as restricting a child's freedom is contradictory: there is no ghostly pre-conception "potential child" whose free will to exist must be respected. Basing identity on genes would represent the worst kind of identity politics--identities should not be protected above people, and eliminating Parkinson's disease is different from eliminating those who suffer from it.

Deciding which modifications are appropriate is merely a new form of the question, "What is the good?" If we can change our child's genes, we will have a responsibility to choose traits that will make our child's life better, whatever we may believe the good life to be. It may involve being exceptional; it may involve being average; it may involve being a happy pig or an unhappy Socrates. But these decisions are no more (and no less) complex than a thousand other ethical concerns. To refrain from them simply because the buzzword "genetic engineering" is involved does not guarantee a child an "open future" but rather a random future, a Russian roulette future. No child is made more "free" if his or her hair color, number of limbs or even sexual orientation is chosen by chance rather than design.

To the extent that genetic engineering is dangerous, the danger must lie with the parents rather than the children. The greatest concern of Will and of Leon Kass, the ethicist whose work he cites, is that the genetic engineering would invert the Nicene Creed: children would be created, not begotten--human artifacts bereft of mystery, dignity and individual worth. Parents would consider their children as playthings; in short, humans would play God.

These objections, however, confuse the justifications for our moral beliefs with the contingent emotions that accompany them. I may feel a sense of awe at genetic individuality, but do I love my children only because I could not have predicted the color of their eyes? Respect for others' lives and well-being is too fundamental to be grounded in surprise; the argument has nothing to do with the morality of genetic engineering and everything to do with how other people (presumably bereft of Will's keen moral sense) will react.

In the end, no better argument is provided for the immorality of genetic engineering than the revulsion it inspires. Kass, indeed, titles his essay "The Wisdom of Repugnance" and attacks genetic engineering as evil because it is unsettling. But moral theory should be more than a summation of the circumstances under which one gets the willies. Genetic engineering is indeed "inhumane" if we think only of those things to which humans have historically been accustomed--but then so is the railroad, wearing clothes and refraining from killing one another. Reasons are required to decide which new practices are acceptable and which beyond the pale.