Third, I reject Savulescu’s procreative beneficence principle because I reject its assumption that we can identify nondisease-related traits that clearly make one’s life better. Among people with a normal IQ, good memory, numeracy, and literacy are useful for a successful life, but it is by no means clear that enhancing any one of these values to a supernormal level would result in a child having a better life. The interaction of gene traits with one another and with the environment is too complex to allow the kind of predictive confidence about any trait that would be needed to apply Savulescu’s principle.

Let me illustrate this complexity with a story. In college, I had two roommates. (For privacy’s sake I’m changing their names.) John  graduated cum laude, went on to a fine Ivy League law school, and reached the apogee of his career when he was elected mayor of his small hometown. I was the best student of the three, graduating summa cum laude and having a solid and satisfying career as an academic ethicist. Harry, was by far the poorest student among us: he barely applied himself, earned straight C’s, and couldn’t get into a top law school. As a result, Harry moved into an arcane field of law at a lesser New York firm, and eventually rose to the top of the new field of merger and acquisition law. Today, Harry  is an extremely wealthy financial industry attorney, and has served as trustee of Brown University, our alma mater.

I am not telling this story to argue that money is the measure of the man. Nor am I saying that any of the traits that led my roommates and me into our lives are genetically based. I offer this anecdote only to indicate how difficult—if not impossible—it is to predict that any character trait, genetic or otherwise, will lead to worldly success much less to happiness. This means that, above and beyond striving to help their offspring have normal health, parents are under no obligation to use genetic technologies to provide those children with nondisease-related genetic enhancements.

If parents are under no obligation to use gene editing for enhancement purposes, may they ethically do so? Should parents be allowed to pursue such genetic enhancements, at least when they’re shown to be sufficiently safe?

This is a complex question that I have written a book about (Babies by Design, 2007). There are many reasons people fear the use of genetics for nondisease-related enhancements. One  fear is that money and genes will work together to produce a “genobility,” a society marked by genetically increased social inequalities. This could happen on a national or international basis. Another is the fear that, in the quest to have athletically gifted children, parents will spark an “arms race,” seeking positional advantage for their children, that concludes by advantaging no one and maybe even harming them. An analogy here is to sports doping which, if widely pursued, benefits no one and risks damaging the individual athletes.

I have no easy answer to the question of whether these ethical concerns or others are so significant that we should try to prohibit parents from these choices.

But I do know that parents seeking such enhancements will likely be disappointed. As I said, parents are under no obligation to pursue genetic enhancements. Furthermore, it’s probably foolish to try to secure the best life possible for one’s child by genetic means. We cannot identify what makes for a best life in this connection. The healthy natural human genome has enough variety in it to let any child successfully navigate the world and fulfill his or her own vision of happiness.