Why do people believe the unbelievable? Why do fictional ideas so often inspire real-world action-sometimes joyful, sometimes destructive-while the people inspired by them never recognize that they are fictional? In Imaginary Realities, Jeffrey Jensen Arnett explores the psychological and cultural forces that lead people to embrace beliefs that defy logic yet shape lives, societies, and history. From religious and magical thinking to conspiracy theories and superstitions, Arnett reveals how these "imaginary realities" help us make sense of a chaotic world and why we adhere to them even when they mislead us. This groundbreaking book examines the psychological roots of irrational beliefs and how they soothe anxiety and foster social cohesion; how they underlie the double-edged sword of moral egoism, which motivates many of our best and worst behavior; the surprising role of imaginary realities in joy, humor, and group celebration; and the looming threats posed by modern myths surrounding AI, ecological collapse, and genetic engineering. With clarity, insight, and cultural depth, Imaginary Realities challenges readers to rethink what we believe and why.