Chekhov's Gun

"The stone itself is meaningless. This situation calls for something, and at this point in time it just happens to be this stone. Anton Chekhov put it best when he said, "If a piston appears in a story, eventually it's got to be fired."
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What Chechov was getting at is this: necessity is an independent concept. It has a different structure from logic, morals, or meanings, Its function lies entirely in the role it plays. What doesn't play a role shouldn't exist. What necessity requires does need to exist. That's what you call dramaturgy. Logic, morals, or meanings don't have anything do with it. It's all a question of relationality. Chechov understood dramaturgy very well."

Kafka on the Shore, Haruki Murakami

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http://en.wikipedia.org/wiki/Chekhov's_gun

It is interesting see the statement of Chekhov's gun. A very similar issue exists in information theory, under the name of 'information criteria'. Roughly, an information criterion suggests us to remove unnecessary things as much as we can in a mathematical way.  It says that "What doesn't play a role shouldn't exist. What necessity requires does need to exist.", as in the quote. Beautiful.