raisonneur [ˌrɛz əˈnɜr] n.
1.) A character in a play, etc., who gives expression to the author's message, standpoint, or philosophy (O.E.D. 2nd Ed.).
Etymology: French, lit. ‘one who reasons or argues’.
"What is the true role of the raisonneurs, and what do they stand for? There is a distinct family likeness between the two Aristes (in L'Ecole des maris and Les Femmes savantes), Chrysalde (L'Ecole des femmes), Cleante (Tartuffe), and Beralde (Le Malade imaginaire): all of these are mature characters 'd'un certain age', standing somewhat to one side of the dramatic action, but showing a sympathetic interest in the fortunes of the central figure, with whom they are connected by family ties or by longstanding friendship" (Moliere: A Playwright and His Audience, W. D. Howarth, 1982).