In pragmatics, a subdiscipline of linguistics, an implicature is something the speaker suggests or implies with an utterance, even though it is not literally expressed. Implicatures can aid in communicating more efficiently than by explicitly saying everything we want to communicate. The philosopher H. P. Grice coined the term in 1975. Grice distinguished conversational implicatures, which arise because speakers are expected to respect general rules of conversation, and conventional ones, which are tied to certain words such as but or therefore. Take for example the following exchange:
A (to passerby): I am out of gas. B: There is a gas station 'round the corner.
Here, B does not say, but conversationally implicates, that the gas station is open, because otherwise his utterance would not be relevant in the context. Conversational implicatures are classically seen as contrasting with entailments: they are not necessary or logical consequences of what is said, but are defeasible (cancellable). So, B could continue without contradiction:
B: But unfortunately it's closed today.
An example of a conventional implicature is "Donovan is poor but happy", where the word but implicates a sense of contrast between being poor and being happy.
Later linguists introduced and refined different definitions of the term, leading to somewhat different ideas about which parts of the information conveyed by an utterance are actually implicatures and which are not.
Conversational implicature Grice was primarily concerned with conversational implicatures. Like all implicatures, these are part of what is communicated. In other words, conclusions the addressee draws from an utterance although they were not actively conveyed by the communicator are never implicatures. According to Grice, conversational implicatures arise because communicating people are expected by their addressees to obey the maxims of conversation and the overarching cooperative principle, which basically states that people are expected to communicate in a cooperative, helpful way.
Standard implicatures The simplest situation is where the addressee can draw conclusions from the assumption that the communicator obeys the maxims, as in the following examples. The symbol "+>" means "implicates".
Quality It is raining. +> I believe, and have adequate evidence, that it is raining. Moore's paradox, the observation that the sentence "It is raining, but I don't believe that it is raining" sounds contradictory although it is not from a strictly logical point of view, has been explained as a contradiction to this type of implicature. However, as implicatures can be cancelled (see below), this explanation is dubious.
Quantity (i) A well-known class of quantity implicatures are the scalar implicatures. Prototypical examples include words specifying quantities such as some, few, or many: John ate some of the cookies. +> John didn't eat all of the cookies. Here, the use of some semantically entails that more than one cookie was eaten. It does not entail, but implicates, that not every cookie was eaten, or at least that the speaker does not know whether any cookies are left. The reason for this implicature is that saying some when one could say all would be less than informative enough in most circumstances. The general idea is that the communicator is expected to make the strongest possible claim, implicating the negation of any stronger claim. Lists of expressions that give rise to scalar implicatures, sorted from strong to weak, are known as Horn scales: all, many, some, few ..., four, three, two, one (cardinal number terms) always, often, sometimes and, or necessarily, possibly hot, warm etc.
Negation reverses these scales, as in this example: She won't necessarily get the job. +> She will possibly get the job. "Not possibly" is stronger than "not necessarily", and the implicature follows from the double negation "She will not [not possibly] get the job".
Here are some further implicatures that can be classified as scalar: I slept on a boat yesterday. +> The boat was not mine. This is a common construction where the indefinite article indicates that the referent is not closely associated with the speaker, because the stronger claim "I slept on my boat yesterday" is not made.
The flag is green. +> The flag is completely green. If this is the strongest possible claim, it follows that the flag has no other features, because "The flag is green and some other colour" would be stronger. In other words, if it did contain other features, this utterance would not be informative enough.
Quantity (ii) The second quantity maxim seems to work in the opposite direction as the first; the communicator makes a weaker claim, from which a stronger one is implicated. Implicatures arising from this maxim enrich the information contained in the utterance: He drank a bottle of vodka and fell into a stupor. +> He drank a bottle of vodka and consequently fell into a stupor. I lost a book yesterday. +> The book was mine. There is extensive literature, but no consensus on the question which of the two quantity maxims is in operation in which circumstances; i.e. why "I lost a book yesterday" implicates that the book was the speaker's, while "I slept on a boat yesterday" usually implicates that the boat wasn't the speaker's.
Relation/relevance That cake looks delicious. +> I would like a piece of that cake. This statement taken by itself would be irrelevant in most situations, so the addressee concludes that the speaker had something more in mind.
The introductory example also belongs here: A: I am out of gas. +> I need to get gas. B: There is a gas station 'round the corner. +> The gas station is open.
Manner (iv) The cowboy jumped on his horse and rode into the sunset. +> The cowboy performed these two actions in this order. Being orderly includes relating events in the order they occurred.
Clashes of maxims Sometimes it is impossible to obey all maxims at once. Suppose that A and B are planning a holiday in France and A suggests they visit their old acquaintance Gérard: A: Where does Gérard live? B: Somewhere in the South of France. +> B does not know where exactly Gérard lives. B's answer violates the first maxim of quantity as it does not contain sufficient information to plan their route. But if B does not know the exact location, she cannot obey this maxim and also the maxim of quality; hence the implicature.
Floutings The maxims can also be blatantly disobeyed or flouted, giving rise to another kind of conversational implicature. This is possible because addressees will go to great lengths in saving their assumption that the communicator did in fact – perhaps on a deeper level – obey the maxims and the cooperative principle. Many figures of speech can be explained by this mechanism.
Quality (i) Saying something that is obviously false can produce irony, meiosis, hyperbole and metaphor: When she heard about the rumour, she exploded. As it is improbable that she really exploded, and it is highly unlikely that the speaker wanted to lie or was simply mistaken, the addressee has to assume the utterance was meant to be metaphorical.
Quantity (i) Utterances that are not informative on the surface include tautologies. They have no logical content and hence no entailments, but can still be used to convey information via implicatures: War is war.
Damning with faint praise also works by flouting the first quantity maxim. Consider the following testimonial for a philosophy student: Dear Sir, Mr. X's command of English is excellent, and his attendance at tutorials has been regular. Yours, etc. The implicature here is that the student is no good, since the teacher has nothing better to say about him.
Relation/relevance B's answer in the following exchange does not seem to be relevant, so A concludes that B wanted to convey something else: A: Mrs Jenkins is an old windbag, don't you think? B: Lovely weather for March, isn't it? +> Watch out, her nephew is standing right behind you! (or the like)
Manner (iii) This utterance is much more long-winded than "Miss Singer sang an aria from Rigoletto" and therefore flouts the maxim "Be brief": Miss Singer produced a series of sounds corresponding closely to the score of an aria from Rigoletto. +> What Miss Singer produced cannot really be described as an aria from Rigoletto.
Particularized versus generalized implicatures Conversational implicatures that arise only in specific contexts are called particularized, while those that are not or only slightly context dependent are generalized. Many of the examples above rely on some context, making them particularized implicatures: thus, "War is war" can refer to different properties of war, or things expected to happen during war, depending on the situation in which it is uttered. Prototypical examples of generalized implicatures are the scalar implicatures. Particularized implicatures are by far the more common kind.
Properties Grice attributed a number of properties to conversational implicatures:
They are defeasible (cancellable), meaning that the implicature may be cancelled by further information or context. Take the examples from above: That cake looks delicious. +> I would like a piece of that cake. versus: That cake looks delicious, but it looks too rich for me. (implicature defeated)
A: Did John eat some of the cookies? B: He certainly did eat some of the cookies. In fact he ate them all.
They are usually non-detachable in the sense that they cannot be "detached" by rephrasing the utterance, as they are consequences of the meaning and not the wording. The obvious exception are implicatures following from the maxim of manner, which explicitly relies on the phrasing. Thus, the following utterances have the same implicature as above: That fruit cake there looks appetizing. The dessert you brought is really mouthwatering.
Conversational implicatures are calculable: they are supposed to be formally derivable from the literal meaning of the utterance in combination with the cooperative principle and the maxims, as well as contextual information and background knowledge.
They are non-conventional, that is, they are not part of the "conventional" (lexical and logical) meaning of a sentence.
Lastly, they can be context dependent, as mentioned above.
Opting out of the cooperative principle The cooperative principle and the maxims of conversation are not mandatory. A communicator can choose not to be cooperative; she can opt out of the cooperative principle by giving appropriate clues such as saying "My lips are sealed", or for example during a cross-examination at court. In such situations, no conversational implicatures arise.
Modifications to Grice's maxims Laurence Horn Various modifications to Grice's maxims have been proposed by other linguists, the so-called neo-Griceans. Laurence Horn's approach keeps the maxims of quality and replaces the other maxims with just two principles: The Q-principle: Make your contribution sufficient; say as much as you can (given the quality maxims and the R-principle). The R-principle: Make your contribution necessary; say no more than you must (given the Q-principle).