Why does deception characterize human behavior, from intimate relations between romantic partners to subterfuge and espionage between nation-state rivals? Deceptions are conditions, actions or statements that hide truth, mislead others, obscure reality, promote ideas or images that do not exist. Human deceptions can be conscious and deliberate, or subconscious and without awareness, but deceptions almost always are intended to benefit the deceiver. Self-deception, perhaps unique to humans, offers special insight. Why would evolution select for deceiving ourselves?