I've been working through some material on rhetorical critical approaches to New Testament studies, as of late, in preparation for my presentation at SBL later this year. While it seems to be gaining acceptance and adherents, rhetorical criticism remains somewhat criticisized as a lens for interpreting biblical texts. Critics often argue that because our knowledge of the education of the biblical authors is limited, we don't know whether they were trained in the canons of classical rhetoric. Thus, they say, it is illegitimate to evaluate and interpret their writings based on those canons.
A question may be posed in response, though: Do the writings of the biblical authors evidence an awareness of and proficiency in classical rhetoric? If we answer this question affirmatively, then it would seem rhetorical categories are not only appropriate but called for with regard to the texts which would appear to use them. If the writer evidences facility with ancient rhetorical convention, then to read the text through a rhetorical-critical lens would be to read the text on its own terms. We don't need to have explicit data about the author's education to judge whether his writings indicate a knowledge of rhetoric. In my current project, I aruge that 2 Peter 3 is structured with a rather elegant rhetorical transition device. Is there external evidence that Peter had classical oratory training? No. But there is internal evidence that he was familiar with this particular device and put it to use in the letter.
Let me say as well that I find rhetorical criticism to be much more fruitful in the New Testament letters than I do other genres. The letters were written to be delivered orally upon their arrival at their destination. It makes perfect sense that they would include features to enhance the oral delivery of the letter/speech. So, while I might read Romans through a rhetorical lens, I would hesitate to read Mark that way.
So, is rhetorical criticism an appropriate method for studying the New Testament? The answer is that it is more appropriate in some places and less in others. If the letters evidence rhetorical features, then we should allow the text to determine our method and analyze them in light of those features. Evidence for rhetorical features is harder to demonstrate in narratives. So, we should be more cautious as we approach those texts.