It has been said that a writer is very like God: When he's creating a story -- a world -- he can do whatever he likes, with no restrictions other than those he himself chooses to accept. But while this notion is undeniably attractive, it is, at best, only partially true. Why? Because the "writer as God" concept tacitly presumes that the writer is completely independent of any other person... and he's not.

A writer -- any writer -- needs readers. Without readers, a writer is nothing.

When a writer creates a story, he's crafting an set of lies (and lies they are, at least in the case of a fictional narrative) for his readers to accept for whatever length of time they spend reading that story. The catch is, the reader's acceptance -- his 'willing suspension of disbelief' -- comes with some strings attached; so although a writer can indeed put anything his heart desires into his stories, there are some things that a prudent writer won't do, lest he forfeit his audience.

One thing a prudent writer doesn't do, is contradict himself. He can lay down whatever rules he likes for a story, but once he has established some specific Rule X, he is obligated to stick with Rule X for the duration of the story. The set of rules that's established for a story is, reasonably enough, known as 'story logic', and a writer violates story logic at his own peril.

Why does story logic matter? If a writer is indeed just a teller of lies, what difference does one more lie make? The answer is simple: A reader's willing suspension of disbelief only goes so far. To spin a web of words that isn't literally true for the 'real world' is one thing; but if the reader gets the idea that this web of words isn't true for any world (real or otherwise)... well, at that point the writer is screwed. Worse, the writer has screwed himself!

Granted, a violation of story logic isn't necessarily a death sentence for the reader's willing suspension of disbelief, as witness Cinderella (in which the glass slipper shouldn't have stuck around for the Prince to discover) and Citizen Kane (in which nobody was there to hear Kane's last mortal word), among others. Even so, I maintain that writers should always make an effort to avoid violating story logic. Put it this way: "Well, at least X isn't guaranteed to screw me over..." is a damned poor reason to do X. Hell, it isn't even a good excuse!

At this point, it may be worth noting that violations of story logic are usually not intentional; they generally indicate that the writer inadvertently overlooked something, not that the writer deliberately contradicted himself. Unfortunately, an unintended contradiction is still a contradiction, and if a reader's willing suspension of disbelief is dead, it doesn't matter whether it was killed by a deliberate act or by an innocent mistake. Either way, the writer has lost that reader.

One of the best ways for a writer to avoid violating story logic is for him to simply pay attention to what he's doing. As a hypothetical example, consider a fantasy story in which, any time a mage's handedness is mentioned, it turns out that the mage is left-handed. Is the reader likely to get the idea that all mages are left-handed, including the ones whose handedness wasn't explicitly mentioned? Yes, he certainly is -- and once the reader has gotten that idea, the introduction of a right-handed mage is likely to be an unwelcome distraction. It does no good for the writer to complain that the reader ought not have made any assumptions about the handedness of mages, because the reader didn't make any assumptions. Instead, the reader reached a conclusion from the data available to him -- and, note well, that data is strictly limited to whatever the writer put into that story. If the data provided in the story leads to an invalid conclusion, who's to blame but the writer, i.e. the person who put all that data in there in the first place?

Readers are perfectly willing to read an author's story; they are substantially less willing, or able, to read an author's mind. Therefore, a writer should always make sure that whatever kind of logic his story has, the story itself contains sufficient clues that a reasonably diligent reader will not be led astray.