not that I have kids (or will have kids for that matter), but let's say I open the door one morning to get my newspaper (I don't even subscribe to the paper, but let's just say). I look down and see a baby in a basket with a note that says something like: "I cannot raise this child, please care for him/her" (but it wouldn't say him/her; it would say either him or her, but I didn't really want to assign gender to this hypothetical which is probably because I don't want to open myself up to the sentimentality of raising a child of my own by personalizing this fictional baby).

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Here's the bastard now trying to sell you a Coke and a Smile.
So I raise the child, and she (okay, let's just make it a she) gets old enough to comprehend things like Christmas and presents. I'm telling you now that I will resist with all my might the social pressure to teach her about Santa. Honestly, could there be anything worse for our spiritual selves than a vacuous icon of materialism and heartless progess? (Santa is an anagram for Satan; I'm aware of that cute, but tired, little phrase, but please don't put words in my mouth.)
Think of it this way. We're led to believe that the better a person you are, the more presents you get. The worse you are as a human, the fewer presents. As if this weren't selfish and petty enough for childhood development, it's really disguising a horrible classist injustice (Hey! save that Karl Marx shit for grad school, ass! I'm making a real point here.) the way you might cover a razor blade with chocolate and call it a bonbon.
Honestly, what does a poor kid who gets one or two presents think of himself when compared to the rich kids that might get a roomful? If they believe in Santa, they're bad kids, and the rich ones are good kids. It perpetuates class separation.
Most people say they don't think of it that way but that they teach Santa to their kids because it gives them something to believe in. Believe in? How about the holiday's celebration of the birth of Jesus? (okay, I'm serious as fuck, motherfucker; don't be bringin' that "reason for the season" bullshit around me; I'm making another point.)

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All hail our new Holiday God: Kon-Trohl-Ahr!
I'm not saying you have to teach about Jesus, but obviously there are spiritual traditions associated with Hannukah as well as Winter Solstice. Worship what you want. But a time of year set aside for various cultures has been usurped by a white-beared fatass that is perpetuated by TV, movies, and the retail industries under the guise of "the spirit of the season" and "you have to believe" and "the joy of giving" when all they really want is your money. It's just a sentimental appeal to your heartstrings, which are connected to your wallet.
So no, I don't believe in Santa Claus, nor do I want my (hypothetical) children to believe in him. They will believe (hypothetically) in something I hope, but it won't be that greedy clown.