What we value, like, endorse, want, and prefer changes over the course of our lives. Sometimes this is a result of decisions we make—such as when we choose to become a parent or move to a new country—and sometimes it is caused by forces beyond our control—such as when our political views change as we grow older. This poses a problem for any theory of how we ought to make decisions. Which values and preferences should we appeal to when we are making our decisions? Our current values? Our past ones? Our future ones? Or some amalgamation of all of them? But if that, which amalgamation? This book presents a theory of rational decision-making for people whose values have changed in the past and might change again in the future. It begins with expected utility theory, the orthodox theory of rational choice, and raises the problem of choosing for changing selves in that context. It then offers a new decision theory that avoids the problem. In the process, the book considers a host of related problems: Is it rational to give less weight to your far future preferences than to those in your near future? Can we have moral obligations to pursue the goals of our past selves? Do we know enough about our future preferences to make rational decisions that are sufficiently sensitive to them? How should we combine competing sets of values into a single set?