This book reviews the recent behavioural economic literature on the "self". First, intertemporal choice as the outcome of a conflict between multiple selves is examined. Identity in economics is discussed, as well as possible selves in economics, and a consideration of how intentional self-change occurs. The self-system is multifaceted and dynamic, with different self-representations activated at different times. Comparison between the actual self and the ideal self has important motivational consequences. Lastly, an examination of the evolutionary emergence of social preferences in the long run is presented.