We raise our kids to be truthful. We teach them about the laws of physics.
And then we tell them that nine flying reindeer pull an immortal fat man and his sleigh through the sky so that he can deliver gifts to millions of kids around the world one night a year.
Is it bad that we lie to our kids about Santa?
Though lying can be an awfully convenient parenting crutch - "Sorry, sweetheart, but the police might arrest you if I let you have more candy, so we better not" - it's generally best to keep it to a minimum, both to develop trust between yourself and your child and to lead by example.
Except in December.
Because - guess what? Not only is the Santa myth harmless, but it might actually be good for kids' cognitive development. Fantastical stories foster a type of imaginative play that sparks creativity, social understanding and even - strange as it may sound - scientific reasoning.
First: Let go of any guilt you have about duping your kids. Santa belongs in the "good lie" pile, because parents invoke him for their kids' sake; bad lies are the ones parents use to deflect blame or avoid responsibility - "We can't go to the playground today because it's closed," when really, you're just too lazy to get off the couch.
By the time children learn the truth about Santa Claus (which is usually by age 8, according to Jacqueline Woolley, a psychologist at the University of Texas at Austin), they typically understand the difference between these types of lies, so they don't resent their folks or suddenly think that across-the-board lying is OK.
(For that matter, kids also do not reject religion, develop post-traumatic stress disorder or become drug addicts after learning that Santa is not real, as one fiercely anti-Santa website claims.)
What Kris Kringle does do is feed the imagination. Kids picture him managing his elves at the North Pole, soaring through the sky or squeezing through chimneys.
Sometimes children participate in the fantasy themselves, adopting the role of Rudolph or Mrs. Claus in games with their friends. These forms of play may cultivate a set of skills known as "theory of mind," which helps kids predict and understand other people's behavior. (Children with emotional disorders such as autism typically have theory-of-mind problems.)
For example, a 1997 study by University of Oregon psychologist Marjorie Taylor, author of "Imaginary Companions and the Children Who Create Them," found that, regardless of their intelligence, 4-year-olds who frequently engage in fantasy play are also better able than other kids to distinguish appearances from reality (they know that a pink rabbit held behind a color filter is still pink), understand other people's expectations (they know people will assume that a crayon box contains crayons, even if the box actually contains a small toy) and know that perceptions depend on context (they know that people will identify images differently depending on how much of them they see).
Taylor's more recent work suggests that preschool and school-aged kids who lead rich fantasy lives - for instance those who have imaginary friends - have a better understanding of emotions, too.
Fantasy play also forces kids to think through hypothetical or counterfactual scenarios, which bolsters their reasoning skills. What will happen if the elves don't finish by Christmas Eve? What would Christmas be like if Santa didn't exist?
It's even possible to teach kids the truth about Santa in a positive way: just give them the tools to figure it out for themselves, Woolley says. If they ask you point blank, "Does Santa really exist?" answer with questions of your own: What do you think? Are you starting to think he doesn't? Why?
Then - because if they're inquiring, they're probably ready to learn the truth - start outing the lie.
Write a letter from Santa in your own handwriting or hide the stocking stuffers in a slightly too-obvious place.
That way, any pain your child feels over losing Santa will be softened by a sense of pride: You can't pull one over on me anymore!
Except maybe with the tooth fairy.