Since rhetorical proof is never a completely necessary proof, the thinking man who gives his adherence to the conclusions of an argumentation does so by an act that commits him and for which he is responsible. The fanatic accepts the commitment, but as one bowing to an absolute and irrefragable truth; the sceptic refuses the commitment under the pretext that he does not find it sufficiently definitive. He refuses adherence because his idea of adherence is similar to that of the fanatic: both fail to appreciate that argumentation aims at a choice among possible theses; by proposing and justifying the hierarchy of these theses, argumentation seeks to make the decision a rational one. The role of argumentation in decision-making is denied by the sceptic and the fanatic. In the absence of compelling reason, they both are inclined to give violence a free hand, rejecting personal commitment.
Chaim Perelman and Lucie Olbrechts-Tyteca, The New Rhetoric.