2300 years ago, Aristoteles built up a very well-balanced system on the arts of discovering and communicating truth from the mind of an author to the mind of an audience. And he called it rhetoric. And so do we, still.
Rhetoric is the art of finding in any given subject matter the available means of persuasion, and this persuasion is achieved by means of logos, pathos, and ethos.
LOGOS requires one to convince an audience by proving the truth of what one is saying.
PATHOS requires one to put an audience into a frame of mind favorable to one’s purpose, principally by working on the emotions.
ETHOS requires one to inspire in the audience confidence in one’s character, competence, good sense, and good will.
In other words, one must know not only what to say but how to say it effectively, and in a well disposed order.
Everything about the making of a documentary could not have been said more succinctly.