Speaker meaning, what is said and what is implicated

[First Paragraph] Unlike so many other distinctions in philosophy, H P Grice's distinction between what is said and what is implicated has an immediate appeal: undergraduate students readily grasp that one who says 'someone shot my parents' has merely implicated rather than said that he was not the shooter [2]. It seems to capture things that we all really pay attention to in everyday conversation'this is why there are so many people whose entire sense of humour consists of deliberately ignoring implicatures. ('Can you pass the salt?' 'Yes.') Unsurprisingly, it was quickly picked up and put to a wide variety of uses in not only in philosophy but also in linguistics and psychology. What is surprising, however, is that upon close inspection Grice's conception of implicature turns out to be very different from those at work in the literature which has grown out of his original discussion. This would not be much of a criticism of this literature were it not for the fact that discussions of implicature explicitly claim to be using Grice's notion, not some other one inspired by him (generally going so far as to quote one of Grice's characterisations of implicature). This still would not be terribly interesting if the notion Grice was actually carving out had little theoretical or practical utility. But I will argue here that Grice's own notion of implicature, one quite different from the ones most of us have come to work with, is in fact far more interesting and subtle than that which has been attributed to him.