He is referring to a recent december test...the one I took... Dec 04.I am 100% certain (philosophy/logic dude here) that this is both X implies Y and Y implies X. It is what is known as a "biconditional" or a "material equivalence."Further, there is NO distinction between if BUT only if and if AND only if.

Quote from: bass on March 30, 2006, 05:45:52 PMHe is referring to a recent december test...the one I took... Dec 04.I am 100% certain (philosophy/logic dude here) that this is both X implies Y and Y implies X. It is what is known as a "biconditional" or a "material equivalence."Further, there is NO distinction between if BUT only if and if AND only if."X does such and such if, but only if, Y does also."Why does X do such and such every time Y does?Billy walks the dog if, but only if, Sally does also ==> Sally walks the dog if, but only if, Billy walks the dog. What? How does that follow? I think "if but only if" is a crappy way of wording conditions.

Think of two conditionals. A if B. A only if B. First is B=>A, second is A=>B. It goes both ways (and in the negative).