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.).