Passage Summary: Even though choruses and narrators do similar jobs, they aren't the same because choruses can sometimes be unreliable or inconsistent.

Conclusion: A play's chorus and a novel's narrator are not equivalent entities.

Reasoning: Unlike narrators, the information provided by a chorus is occasionally inconsistent with the rest of the work.

Analysis: The author is trying to prove a difference between two things by pointing out a flaw in one of them. For this logic to hold up, the author must assume that the other thing—the narrator—does not share that same flaw. If narrators were also occasionally inconsistent, the 'difference' would disappear. Therefore, the argument relies on the necessary assumption that narrators in novels are generally consistent with the information in their stories.