Case in point: Star Wars. George Lucas, like other human beings, makes mistakes. Here's Han Solo describing his ship in Episode IV: A New Hope:
"You've never heard of the Millennium Falcon?...It's the ship that made the Kessel Run in less than twelve parsecs."Here's the problem: a parsec is equivalent to about 3.26 light years or 19 million miles; it's a measure of distance, not time. It makes no sense to say you got from point A to point B "in less than" a certain distance. Lucas has plainly made a mistake here. Perhaps he was drawn in by the science-fiction quality of the word, or interpreted the "sec" portion to mean "seconds." In any case, there's no getting around this. The Stars Wars canon has been shown to contain errors.
Or has it?
For the real Star Wars fanatics, this anomaly absolutely requires an in-universe explanation. Here's what they came up with. The route of the Kessel Run goes through the Maw, a dangerous cluster of black holes. Slower ships must take a more circuitous route to avoid being sucked in, but the Millennium Falcon is fast enough that it can veer closer to the black holes, thus reducing the overall distance needed to complete the journey.
It kind of makes sense, although it's still a stretch. The dialogue still sounds awkward, and there's just no reason not to express the duration of the journey in terms of time. The black holes may even have been invented just to resolve the error. For Star Wars fans, though, this explanation is good enough; they can continue accepting this universe as internally consistent. And that's fine: it's all in fun, and there's no harm in continuing to suspend disbelief as long as you understand that it's all pretend.
But what about biblical inerrancy, which unlike the previous example has serious effects on reality? Take the fervor for a believable Star Wars universe and multiply it by a thousand. That's the magnitude of motivation Christians have for maintaining the Bible's internal consistency. And like Star Wars fans, they will cling to any ad hoc explanation, any interpretation of language or history that will preserve their dogma. Often their excuses are significantly less convincing than the example above. But when you have such low standards for accepting explanations, inerrancy is no longer an impressive feat. You can apply the same principle to any work of fiction—be it Star Wars films or the Quran—and get the same result.