Abstract: This book has four loosely connected parts. Part One discusses some ways in which theories about morality and rationality can be self-defeating. Such theories give us certain aims, but also tell us to act in ways that frustrate these aims. If these theories are revised, these objections can be partly met.Part Two discusses the relations between what a single person can rationally want or do at different times, and what different people can rationally want or do. I also discuss the rationality of four attitudes to time: temporal neutrality, and the three kinds of bias towards the present, the near, and the future.Part Three discusses personal identity, or what is involved in our continuing to exist throughout our lives. Most of us, I argue, have certain beliefs about this subject that are false, but hard to give up. If we accept these claims, they may change some of our emotions or attitudes, and we should revise some of our beliefs about both rationality and morality.Part Four discusses our obligations to future generations, and some related questions about what would be better or worse futures for mankind. The most difficult question here, which I fail to answer, is about the relative importance of the number of people who will exist, and the quality of life of these people.

Keywords: consequentialism, ethics, future generations, morality, Parfit, personal identity, persons, philosophy of mind, rationality, reasons, self-interest, time