  Early work by Savulescu (2001), for instance, argues that parents have an obligation to produce the best children possible. This obligation cannot be owed to any particular child (given the non-identity problem), but is an impersonal obligation, to make the world a better place. If parents are using pre-implantation genetic diagnosis, they should always choose the embryo with the best chances at the best life. Non-disease traits, as mentioned earlier, can have significant effects on how well people’s lives go. Savulescu imagines that the rational parent could make no other decision but to avoid the negative linkages and promote the positive ones, where possible.