wws@siemens.UUCP (William W Smith) (07/25/84)
If all men must die, some men are female. If all men (mankind) must die, some men (males) are female. Without the parenthesized comments, this statement is true but very disconcerting in English. With the comments, you the irony of the statement is seen as a fallacy in reasoning. In logic it is a perfectly acceptable statement, "If all men (mankind) must die, some men (mankind) are female." It is also an invalid deduction: "If all men (males) must die, some men (males) are female." Submitted for your approval by Bill Smith ihnp4!mhuxi!princeton!siemens!wws
jacob@hpfclo.UUCP (jacob) (08/07/84)
It might be "a perfectly acceptable statement," but it is an invalid deduction no matter which way to put it. Let's formalize the first statement ("A" = "for all", "E" = there exists): (A x)(Man(x) -> Die(x)) --> (E y)(Man(y) ^ Female(y)) Do you still claim it is a tautology? Same goes for the second, less ambiguous statement: (A x)(Human(x) -> Die(x)) --> (E y)(Man(y) ^ Female(y)) or, for that matter: (A x)(Human(x) -> Die(x)) --> (E y)(Human(y) ^ Female(y)) None of the above, independently, are true, so they are not valid deductions. The only reason the second formulation "feels better" is that we rely on knowledge that there are female humans. But that is the conclusion of the statement, so if we accept it as a premise, we don't even need to know if they die or not. Jacob Gore ihnp4!hpfcla!jacob