David Post discusses why writing law exams are tough:

I’m convinced that this is what many students find inscrutable about the law — on an anthropology exam, or a history exam, or a biophysics exam, you’re trying to show how much you know about the subject matter (and therefore to hide the questions the answer to which you don’t know). In law, it’s the opposite — instead of running away from the things you don’t understand, you actually have to highlight them, because that’s where the action is, and that’s how you demonstrate that you really understand the subject matter at hand. It’s very strange, and very counter-intuitive, but it is something that all good lawyers have to know how to do.

And, I would argue, something that good literary scholars know as well.