The progress of biology, neuroscience and computer science makes it clear that some time during the twenty- first century we will master the technologies of mind and life. We will build machines more intelligent than ourselves, and modify our own brains and bodies to increase our intelligence, live indefinitely and make other changes. We live together according to a social contract, consisting of laws, morals and conventions governing our interactions. This social contract is based on assumptions we rarely question: that all humans have roughly the same intelligence, that we have limited life spans and that we share a set of motives as part of our human nature. The technologies of mind and life will invalidate these assumptions and inevitably change our social contract in fundamental ways. We need to prepare for these new technologies so that they change the world in ways we want