 Their syllogism as stated above, though deductively valid, is utterly unpersuasive. The reason is that the instances of audibility (H), are coextensive with sound (p). Thus, there is no independent empirical evidence to support the universal statement that whatever is audible is eternal. Requiring that there be at least some thing different from sound which is both audible and eternal is an obvious and plausible way to eliminate such patently unpersuasive syllogisms. Dignāga, therefore, rules out the syllogism as a bad syllogism, rather than, as we would, accept it as a valid syllogism with an unpersuasive premiss. (See also Tillemans 1990.)