So far we have seen that the evolutionary legacy of being a social animal has left us with an anxiety about what and who to trust as well as the finely tuned skills both for detecting cheats and for seeming persuasive. More generally Homo credens needs reliable beliefs in order to function, even to the point of believing distortions. Our belief-fixing skills are underpinned by wiring that usefully turns the “blooming buzzing confusion” of sense data into meaningful order, the same process leaving us prone to swallowing illusions. Going beyond merely perceptual illusions these distorting tendencies extend somewhat to cognitive and narrative illusions with implications for how we understand and interact with each other.

On the principle that the most persuasive liars have persuaded themselves first we have evolved the capacity for self-deception. This profoundly useful, although by definition elusive, quality enables us to flatter ourselves and each other that we are nicer and more in control than a closer look would suggest. Look closely and one can glimpse the mixed motives, cognitive dissonance, and general need to bury awkward desires from view. Who was it who said, “A thought-murder a day keeps the psychoanalyst at bay”? The nature of desire is such that it cannot be suitable for polite company, and so we tell self-serving stories that make us look prettier than we are.