Abstract
It is likely that gene editing technologies will become viable in the current century. As scientists uncover the genetic contribution to personality traits and cognitive styles, parents will face hard choices. Some of these choices will involve trade-offs from the standpoint of the individual's welfare, while others will involve trade-offs between what is best for each and what is good for all. Although we think we should generally defer to the informed choices of parents about what kinds of children to create, we argue that decisions to manipulate polygenic psychological traits will be much more ethically complicated than choosing Mendelian traits like blood type. We end by defending the principle of regulatory parsimony, which holds that when legislation is necessary to prevent serious harms, we should aim for simple rules that apply to all, rather than micro-managing parental choices that shape the traits of their children. While we focus on embryo selection and gene editing, our arguments apply to all powerful technologies which influence the development of children.