by Carl Pierer

After dinner and upon noticing a stain, Abelard ejects: “Oh no, I look like a pig.”
Bertha: “Well, and you've spilled sauce down your tie!”
Often an utterance means something over and above of what it literally says. Is it in such cases always possible to return to the “literal” meaning? Is it possible to sincerely answer the question “Do you think I'm fat?” with “You have nice feet” and only mean that the questioner has nice feet?
To capture and analyse what is going on in these cases, H.P. Grice introduces the term “implicature”. Abelard's statement by itself is usually understood metaphorically; it is rather unlikely that he literally looks like a pig. More plausibly, he means that he looks messy – possibly because he spilled some sauce. This is an example of conventional implicature – an implicature associated with certain set phrases, where the implicature is not depended on the context in which the utterance is made. The second sentence, Bertha's utterance, also seems to carry a meaning above what she literally said. It seems that in this context Bertha suggests precisely the literal meaning of Abelard's sentence. This kind of implicature, which depends on the context, Grice calls conversational implicature.
On the face of it, Bertha's utterance is at best redundant or worse, it does not make sense. If Abelard is really implicating: “Oh no, I've spilled sauce down my tie”, Bertha's repetition of this very fact does not add anything to the conversation. Although this happens all too often, it seems reasonable to suppose that usually people try to contribute to the conversation. In a meaningful exchange (whatever that means), people try to be constructive. This idea is captured by Grice in what is called the Cooperative Principle. Wayne Davis concisely puts the cooperative principle thusly:
“Cooperative Principle. Contribute what is required by the accepted purpose of the conversation.”
For instance, if asked where to have lunch, a person will usually name a place. Another perfectly common reply is: “I'd like to have some lasagne”. Yet, strictly speaking this does not answer the question. In fact, at first sight, it violates the cooperative principle: the purpose of this exchange is to figure out where to go for lunch, so saying what you want to have for lunch is not directly relevant. And still, it is a meaningful contribution, provided that we understand “I'd like to have some lasagne” as implicating “Somewhere where they serve lasagne”.
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