DILEMMA

DILEMMA. - From δὶς λῆμμα (double assumption), a form of reasoning in which, from two or more members of a disjunctive premise, either an identical conclusion or different conclusions are drawn, but always to the opponent’s disadvantage. For example, to the sceptic who asserts the impossibility of knowing the truth, one may object: the assertion is either false or true; in either case truth can be known. Because of its particular structure and dialectical force, the d. was called by s. Girolamo syllogismus cornutus (Epist., 69, n. 2). For its efficacy to be apodictic, the disjunctive premise must encompass all possible cases (sit disinnicio completa), and the conclusion must be based on a necessary and exclusive logical connection (sit consequentia necessaria): if the first condition is lacking, the d. gives rise to “evasion”; if the second is lacking, it may be susceptible to “retortion.”