I was thinking the other day about why I write. I, like many other writer/reader types, am an escapist. I play video games and watch movies in addition to reading and writing. Of these, they are nearly all science-fiction. No historical novels, no romance, and almost nothing that takes place in this reality. As far as setting, characters, and plot are concerned, I prefer something that could not happen in real life (given that science and scientific discoveries are always evolving). I'm not going to presume why this is, I'm sure there are psychological oratories on the purpose of fantasy and escapism. And this is not the place for it.
But when I write, I write to feel the way I did in high school, with fewer responsibilities, and unlimited power - I had money, a car, time to watch movies, and no one who needed something from me. I needed something from them, but no one was tugging on my shirt, demanding I spend time with them, or to get the milk, or to clean the bathroom, or vacuum the floor, or to spend dinner with their parents. Writing is freedom, and maybe more to the point - writing is not being here. I can fall back into another world, but unlike movies, I can control what happens. Some video games are like this, but the game is never 100% of what I want to do. I may want to play GTA:Vice City, but I want to telekinetically throw cars at people, and carpet-bomb buildings from my helicopter, while rescuing my lady fair, and protecting a small teddy-bear like companion. Sometimes when I played Mega Man, I'd imagine I was a robot from the future, or a cyborg fighting against time. But in the story, I totally control what happens. I have a girlfriend, I can wield a damn good gunblade, I have to fight against the forces of hell and back. I can be seduced by naughty, wicked women, and come back STD free (I just can't see what happened, because I couldn't write a sex scene to save my life). I can sail a pirate ship with mermaids, and bounty hunt space zombies. I am freed from the mundaneness of this existence. I can get what I want when I'm writing.
Writing is like escapism where I not only control who I am, but the circumstances around me. The difficulty with that is that I get total freedom, no limitations. So the trick is to make your own limitations, so that what you're writing doesn't seem implausible. Of course, I don't forget that I'm supposed to have a plot, and that I'm not just writing for myself. But besides that, I often write so I can be the person in my stories. This is evident by the fact that all the main characters in my stories are people I either want to be, or am.
I know that one of the slushkillers of getting accepted/rejected is "It’s nice that the author is working on his/her problems, but the process would be better served by seeing a shrink than by writing novels." It's a fine line to try and avoid that, but I'm sure I'm not the first author to make a great work out of a Mary Sue (I'm looking at you Time Traveler's Wife. Yes, you look nothing like Claire, that's right.). The trick is to make it so it's entertaining to the reader in addition to whatever therapy it is for the author. Otherwise it becomes a diary entry. That way, both the reader and the writer can appreciate the escapism. "Jumper" I'm reading right now, is good example of escapist fiction. It's a very realistic portrayal of an eighteen-year-old boy who discovers he can teleport anywhere. This is great escapism because it's something you would never be able to do in real life, if you could do it in real life.
And that seques into another reason I write, which I may or may not elaborate on in the future - power.