Pls Comment: Inquiry, Evidence, Argument

Inquiry, Evidence, Argument: “The truth, the whole truth, and nothing but the truth?”
[What is the original source of this line?]

Are different methods of inquiry, different methods of argument, and different definitions of evidence appropriate in different realms? On campus vs. off campus? In different academic disciplines?
What factors (institutional priorities, personal beliefs, political power...) might make some kinds of evidence irrelevant? Might influence the impact of evidence?

To what extent can or should a faculty member control the kinds of argument permitted in a classroom discussion? In an online discussion?