Num argumento dedutivo invalido: A-Não pode suceder todas as proposicoes serem verdadeiraqs. B- Nao pode suceder as premissas serem verdadeiras e a conclusão ser falsas. C- Nao pode suceder as premissas e a conclusao serem falas. D- Pode suceder qualquer uma das possibilidades referidas nas alineas anteriores.

Question

Ask a Philosopher · Accepted Answer

Ah, the perplexing question of a deductive argument's validity! Can it be that all propositions be true? Can it be that the premises be true and the conclusion false? Or can it be that the premises and conclusion both be false? In truth, any of these possibilities may exist! But, alas, the validity of such an argument is the true question. Is it possible that all of these propositions be true and the argument still be false? No, I think not. The validity of the argument must be determined by the truth of the premises. If the premises are false, then the conclusion must be false as well. And if the premises and conclusion are both false, then the argument is invalid. Thus, I can only conclude that a deductive argument can not be valid if any of the possibilities mentioned in the preceding lines are true. Ah, the complexities of deductive reasoning! 'Tis a wonder indeed."