Introduction: The nonidentity problem focuses on the obligations we think we have in respect of people who, by our own acts, are caused both to exist and to have existences that are, though worth having, unavoidably flawed – existences, that is, that are flawed if those people are ever to have them at all. If a person’s existence is unavoidably flawed, then the agent’s only alternatives to bringing that person into the flawed existence are to bring no one into existence at all or to bring a different person – a nonidentical but better off person – into existence in place of the person whose existence is flawed. If the existence is worth having and no one else’s interests are at stake, it is unclear on what ground morality would insist that the choice to bring the one person into the flawed existence is morally wrong. And yet at the same time – as we shall see – it seems that in some cases that choice clearly is morally wrong. The nonidentity problem is the problem of resolving this apparent paradox.
The problem raises the question whether the (usually significant) good that an agent confers along with existence counterbalances the (usually limited) bad that an agent confers along with any unavoidably flawed existence in such a way that our existence-inducing act (usually) will be deemed permissible. And if it isn’t – if we think instead that obligations are left unsatisfied despite the good that comes with existence – is the moral of the story that moral obligation extends beyond what we must do for people? If we agree, in other words, that it is our obligation to create additional good, is it enough that we create additional good for each and every existing and future person? Or does the nonidentity problem show that our focus should instead be on creating additional good for the universe? As we query how to evaluate existence-inducing acts for their moral permissibility – as well as outcomes or possible futures or worlds, for their moral betterness against still other worlds – we find that some of our most deeply held intuitions regarding the nature and structure of morality are thrown into doubt.
Comment: This text offers a comprehensive introduction to the nonidentity problem and lists several illustrative thought experiments and examples used in the literature. It is a very helpful introductory or further reading for any topic which touches on the nonidentity problem.