Vātsyāyana says inquiry works neither on the unknown nor on the settled, only on the doubtful. Is that a rule for seminars too?

I've been translating the opening of Vātsyāyana's commentary on the Nyāya Sūtra for a study circle, and one sentence keeps stopping me. Reasoning, he says, does not operate on something wholly unknown, nor on something already settled, but on something in doubt.

Doubt (saṃśaya) is in fact one of the sixteen topics the Nyāya Sūtra lists at the start, alongside the means of knowledge and the parts of an argument. Inquiry begins when a person sees two possibilities and cannot yet tell which is true: is that a post or a man in the dusk?

Charles Peirce said something close in "The Fixation of Belief" (1877). Real doubt is an uneasy state that we struggle to escape, and that struggle is inquiry. Elsewhere he mocked "paper doubt", doubting something only because a method tells you to.

What interests me is the practical rule hidden here. In seminars, the students who learn least are often the ones who already know the answer and the ones who have no idea what the question is. Both are outside Vātsyāyana's zone.

For discussion:

• Can a teacher produce real doubt, or only paper doubt?
• Is Vātsyāyana right that we can't inquire into the wholly unknown? What about pure curiosity?
• Is Nyāya's doubt closer to Peirce's or to Descartes's?