The Argument of the Beard

The essence of the argument of the beard (so-called by some logic textbooks) is the tactic used by a respondent to reply to a proponent, "The criterion you used to define a key term in your argument is vague, therefore your use of this term in your argument is illegitimate, and your argument is refuted." This familiar kind of argument tactic is similar to the much more famous heap (sorites) argument of Eubulides, closely associated with the slippery slope argument. This article provides a system of classification for sorting out these three arguments, and related types of argument of interest in informal logic. Resume: La tactique familiere selon laquelle on replique a un adversaire en lui disant, "Le critere que tu as employe pour definir un mot cle dans ton argument est vague, donc ton usage de ce mot est illegitime, par consequent, ton argument est refute," est semblable aux celebres sorites megarites du tas d'Eubulide, et s'associe etroitement a l'argument de la pente glissante. Cet article decrit un systeme de classification qui distingue ces trois types d'arguments et quelques autres qui s'y rapportent dans le cadre la logique informelle.