Most people do not take their daydreams seriously. This book argues that the fantasy of daydreams is central to our lives and essential to our well-being. Far from being a retreat from the world, fantasy plays a major role in shaping it. The book offers evidence that fantasies fuel our behaviour, revealing our secret hopes and fears and helping us transform our lives. Fantasies can soothe us or stimulate us sexually, but more significantly, they let us test possibilities. They deepen our connections with other people. They protect us from precipitate action, they serve as viable life-plans. They heal or undo past defects and old conflicts. They create an ambience of hope for the future, even in seemingly hopeless situatins, and give us the strength to endure.