 But speakers who utter sentences of the form “Some S are P” rarely if ever implicate the denial of “Several S are  P”.[36]  Among the infinity of statements stronger than “Some athletes smoke”, “All athletes smoke” is highly unusual in that people commonly implicate its denial. Since the derivations have the same form whether or not their conclusions are observed to be true, Lepore &amp; Stone (2015: 143ff) call this the “symmetry” problem. The Gricean derivation seems plausible only because we knew antecedently that the conclusion is  true.[37]