To lie is to intentionally mislead others when they expect honest communication.2 This leaves stage magicians, poker players, and other harmless dissemblers off the hook, while illuminating a psychological and social landscape whose general shape is very easy to recognize. People lie so that others will form beliefs that are not true. The more consequential the beliefs—that is, the more a person’s well-being demands a correct understanding of the world or of other people’s opinions—the more consequential the lie.

False encouragement is a kind of theft: It steals time, energy, and motivation that a person could put toward some other purpose.

Big lies have led many people to reflexively distrust those in positions of authority. As a result, it is now impossible to say anything of substance on climate change, environmental pollution, human nutrition, economic policy, foreign conflicts, medicine, and dozens of other subjects without a significant percentage of one’s audience expressing paralyzing doubts about even the most reputable sources of information. Our public discourse appears permanently riven by conspiracy theories.

An unhappy fact about human psychology is probably at work here, which makes it hard to abolish lies once they have escaped into the world: We seem to be predisposed to remember statements as true even after they have been disconfirmed. For instance, if a rumor spreads that a famous politician once fainted during a campaign speech, and the story is later revealed to be false, some significant percentage of people will recall it as true—even if they were first exposed to it in the very context of its debunking. In psychology, this is known as the “illusory truth effect.” Familiarity breeds credence.

Lying is, almost by definition, a refusal to cooperate with others. It condenses a lack of trust and trustworthiness into a single act. It is both a failure of understanding and an unwillingness to be understood. To lie is to recoil from relationship.

Christmas must be marginally more exciting for children who are duped about Santa—but something similar could be said of many phenomena about which no one is tempted to lie. Why not insist that dragons, mermaids, fairies, and Superman actually exist? Why not present the work of Tolkien and Rowling as history? The real truth—which everyone knows 364 days of the year—is that fiction can be both meaningful and fun. Children have fantasy lives so rich and combustible that rigging them with lies is like putting a propeller on a rocket. And is the last child in class who still believes in Santa really grateful to have his first lesson in epistemology meted out by his fellow six-year-olds? If you deceive your children about Santa, you may give them a more thrilling experience of Christmas. What you probably won’t give them, however, is the sense that you would not and could not lie to them about anything else.

Whatever its imagined virtues, faith is the enemy of open and honest inquiry.