What do we owe to people who don't yet exist? Intuitively, it seems to me that we shouldn't, say, cause widespread damage to earth because it will so valuable to our descendants. But can we really be said to be doing something wrong to someone who doesn't exist? And would it be wrong to do something that would cause them never to exist in the first place? It seems that if we can do moral harm to future people, but it isn't wrong to cause them to never exist, then it morally superior to never have children rather to bring children into the world in which you have done the *slightest* damage. (The children, of course, would disagree.) But if it is wrong to cause them to never exist-and, since they would drastically prefer to exist-then we have a tremendous burden to reproduce as much as possible. If it make any difference, I am interested in how these question relates to our burden to reduce catastrophic/existential risks to the human species (global warming, nuclear war, gray goo, etc.).

That's a lot of difficult questions! First: I think we can do wrongto people who don't yet exist. It seems unfair to be less respectful ofsomeone who will be born in, say, 2020 than someone who was born in,say, 1995. Second: it is not obvious that your second question makesmuch sense. You can't do wrong to a being who doesn't exist, never hasexisted and never will exist, simply because there are no such beings!A future being isn't yet around to be harmed, but will be later. But non-existent beings aren't there to be harmed. You go on toconsider a conditional: 'if ... it isn't wrong to cause them never toexist ...' where 'them' is supposed to refer to future people. But ifwe cause there to be no future people then 'them' doesn't refer andthere is no issue about harming them. Still one might wantto argue that we have a duty not to make the planet uninhabitablebecause we have a duty to our species. I am not sure how to justifythat, but the thought seems to have some intuitive appeal.