In this foundational book, Robert Trivers seeks to answer one of the most provocative and consequential questions to face humanity: why do we lie to ourselves? Deception is everywhere in nature. And nowhere more so than in our own species. We humans are especially good at telling others less - or more - than the truth. Why, however, would organisms both seek out information and then act to destroy it? In short, why practice self-deception? To biologists this has long been a mystery. Our sense organs have evolved to give us a marvellously detailed and accurate view of the outside world. So why should natural selection then lead us to systematically distort what we know? After decades of research, Robert Trivers has at last provided the missing theory to answer these questions. What emerges is a picture of deceit and self-deception as, at root, different sides of the same coin. We deceive ourselves the better to deceive others, and thereby reap the advantages. From space and aviation disasters to warfare, politics and religion, and the anxieties of our everyday social lives, Deceit and Self-Deception explains what really underlies a whole host of human problems. But can we correct our own biases? Are we doomed to indulge in fantasies, inflate our egos, and show off? Is it even a good idea to battle self-deception? With his characteristically wry and self-effacing wit, Trivers reveals how he finds self-deception everywhere in his own life, and shows us that while we may not always avoid it, we can now at least hope to understand it.