There is a significant possibility that over the next few decades science will make discoveries of a kind that might allow the doubling of the average human life span, from roughly 76 years now to 150. This development would, for many, represent the realization of a dream: that of enabling people to live much longer lives than at present, holding back death, which has often been seen as an ancient, unbeatable enemy. It would also raise a large number of unprecedented individual and social problems: Would we really want to live to 150? Is such a goal ethical? What would this putative longevity do to our present social structures and arrangements? Would we get a better society or a worse one?