Game theory has a very general scope, encompassing questions that are basic to all of the social sciences. It can offer insights into any economic, political, or social situation that involves individuals who have different goals or preferences. However, there is a fundamental unity and coherent methodology that underlies the large and growing literature on game theory and its applications. My goal in this book is to convey both the generality and the unity of game theory. I have tried to present some of the most important models, solution concepts, and results of game theory, as well as the methodological principles that have guided game theorists to develop these models and solutions.