In each of these cases, there was a mismatch with reality. The person harbored a false belief, but believed it was true. In some cases, the mismatch was due to psychosis, some kind of delusion or malfunctioning of the brain. These people didn’t know that their beliefs were false. In other cases, the mismatch resulted from an intentional lie or distortion, a process that is adaptive, designed to promote self-confidence and manipulate others. When I conjured up images of McEnroe, I momentarily deceived myself. I believed it helped my game. I never thought I was McEnroe. I carried my self-deception honestly. When Hilary Clinton misreported her trip to Bosnia, perhaps she misremembered or perhaps she distorted her memory to convince voters that she had what was necessary to run the country — toughness and international experience. Unfortunately for Clinton, her comment about Bosnia was accompanied by other distortions, which led the American essayist William Safire to write “Americans of all political persuasions are coming to the sad realization that our First Lady... is a congenital liar.” Some cases of self-deception are harmless and even beneficial, as in my illusion of tennis grandeur. Others are only mildly harmful, as in Clinton’s distortion of her political experiences. And yet others are deeply harmful, as when leaders such as Ahmadinejad deny the suffering of millions. The problem is that anyone can harness the power of self-deception for ill gotten gains. Why does our mind play tricks on us, allowing us to believe things that are false? Why didn’t evolution endow us with a reality checking device that is vigilant 24/7? The answer here parallels the refrain carried throughout this book: like its evil sister dehumanization, self-deception is Janus-faced, showing both an adaptive and maladaptive side. Self-deception allows us to protect ourselves from the reality of a current predicament or loss. Self-deception allows us to provide a better personal marketing