This week at the Colgate Writers' Conference (and for those of you who missed the comments of the conference post, I highly recommend this smart, friendly, incredibly fun event), I had a student who had written a very long, complicated novel spanning many years, and incorporating many points of view. And the student broke a major literary taboo: that is, the novel featured a hugely important piece of secret knowledge on which the whole story hinged--and also featured a close third-person narrative from the point of view of the only character who held this piece of knowledge. And yet this character just happened never to think about the vital information.
Generally speaking, I consider this a terrible cheat. It's a fairly common tactic in lousy police procedurals, where the detective's point of view is casually intercut with scenes from the mind of the killer--whose identity and location coincidentally never cross his mind.
Why does this bother me so much? It's a violation of what I consider to be the prime directive of literary narrative: the exploration of consciousness. I'll accept all manner of plot implausibilities, but when a writer makes people think in an impossible way, I become very, very impatient. If you can't trust the narrator to give you an accurate representation of the characters' minds, you can't trust the book at all.
And yet sometimes writers kind of almost get away with it. I just read The Girl Who Played With Fire, the pretty good sequel to Steig Larsson's terrific The Girl With The Dragon Tattoo (I'm not going to review it here, but I can tell you the ending, while exciting, is embarrasingly implausible), and I saw this taboo broken many, many times. A character is suspected of committing three murders. Did she do it? We get 75 pages from her point of view before she happens to think about it. In this case, it nearly works--the character in question has a highly unusual, compartmentalized mind, and you can almost make a case for her not considering her own possible role in the murders over several weeks. Ultimately, though, it's a lame trick, and cheapens the book.
Karin Fossum, on the other hand, pulls it off in The Indian Bride, a superior and highly unusual crime novel; our killer is hidden in plain sight, and from himself, in a very effective literary sleight-of-hand. But it works because it makes sense for the character to think this way. It's never just for Fossum's convenience.
Of course, you can do this easily in the first person--first person narrations are inherently untrustworthy, and sometimes a writer foregrounds this quality, as in Kazuo Ishiguro's great unreliable-narrator novels. But the third-person narrator is supposed to be somebody you trust--somebody who understands the characters entirely, and doesn't let them get away with anything. It's a rule made to be broken, but break it at your own risk.