Often, what people say is not literally what they mean. Thus, in conversations we sometimes infer or conclude the speaker's intention based not only on what was said, but also on what the speaker is trying to achieve. At the dinner table, when you ask if someone "can pass the salt", the persons spoken to derive a meaning that is not the literal meaning of the sentence (you are not querying their ability to actually do so). Such inferences are called implicatures. Implicatures are deductions that are made in accordance with the conversational maxims, taking into account both
- the meaning of the linguistic utterance
- the particular circumstances
in which the utterance is made.
Implicature versus Entailment
Implicature is the relationship between two statements in which the truth of one suggests the truth of the other, but — distinguishing implicature from entailment — does not require it. For example, the sentence Mary had a baby and got married. strongly suggests that Mary had the baby before the wedding, but the sentence would still be strictly true if Mary had her baby after she got married. Further, if we add the qualification "—not necessarily in that order" to the original sentence, then the implicature is cancelled even though the meaning of the original sentence is not altered.
This can be contrasted with cases of entailment. For example, the statement The president was assassinated. not only suggests that The president is dead. is true, but requires that it be true. The first sentence could not be true if the second were not true; if the president were not dead, then whatever it is that happened to him would not have counted as a (successful) assassination. Similarly, unlike implicatures, entailments cannot be cancelled; there is no qualification that one could add to "The president was assassinated." which would cause it to cease entailing "The president is dead.", while also preserving the meaning of the first sentence.
The specialized term implicature was coined by Paul Grice as a technical term in pragmatics for certain kinds of inferences that are drawn from statements without the additional meanings in logic and informal language use of implication.
When we "hide" what we actually want to say behind implicatures, we assume that receiver of the message is aware of the social conventions underlying our utterance. The following "Hagar the Horrible" cartoon depicts an example of a failure of Grice's implicature!
Source of the picture: cse.unsw.edu.au