Grice's Maxims
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Grice's Maxims: \Do the Right Thing" Robert E. Frederking Center for Machine Translation Carnegie Mellon University [email protected] Abstract But is Relevance a well-defined notion? No. • Like the other maxims, Grice's Relevance is a broad, Grice's maxims are hopelessly vague, and in fact harm- general statement that is clearly true at some level, ful, because they form a misleading taxonomy. While his cooperative principle may be useful at a high level but is far too vague to be used directly in compu- of theoretical analysis, it too is vague, and should not tational systems. I believe it is currently an open be directly implemented in computational natural lan- question whether some other approach to relevance guage systems. Answers are suggested to a number of (such as Relevance Theory, discussed below) may be this symposium's topics based on this position. Ex- amenable to precise definition. amples are presented to show that the maxims are too vague and too general, and that they are not re- ally used by computational systems that claim to be based on them. The historical origins of the maxims What distinguishes conversational implica- in Kant's philosophy are revealed. A comparison is • tures from other defeasible inferences in dis- made with Relevance Theory, which seems to provide a better approach to the same phenomena. I conclude course (e.g., default inferences in text under- by suggesting that it may be too early in the history of standing)? I would claim that the only thing that computational linguistics to expect to find such broad distinguishes conversational implicatures as a class is principles. the fact that they can be seen as examples of Grice's principles. In other words, the categories he uses Introduction have no predictive or explanatory power. This is not to say that certain subclasses (such as scalar I will argue in this position paper that Grice's maxims implicatures) do not have useful distinguishing fea- are hopelessly vague, and that while his cooperative tures; only that the Gricean level of description is principle may be useful at a high level of theoretical misleading. analysis, it should not be directly implemented in com- putational natural language systems. From this point of view, there are clear answers to several of the questions this symposium will address: Most models have focused on single classes of • conversational implicature. What problems Is the notion of conversational implicature would arise in integrating them? It is pointless • still useful? What role if any do Grice's max- to consider integrating different classes of conversa- ims and Cooperative Principle still play in tional implicature, based on Grice's taxonomy. His computational and formal approaches? The taxonomy is not of a sufficiently concrete nature to notion of conversational implicature, and the Coop- be fruitfully applied to real implementations. There erative Principle, have been useful and important are significant issues in integrating different types to some researchers in thinking about how language of inference mechanisms in conversation, but Grice's works in real use. But however useful they are for categories are irrelevant to these issues. guiding a researcher's thinking, they are not useful as an actual part of an implementation. The maxims, on the other hand, play no useful role whatsoever in In short, I claim that Grice's Maxims are similar to any computational or formal approaches, even at a the maxim \Do the Right Thing," which any correctly theoretical level. They are in fact harmful, because working natural language system can be said to imple- they form a misleading taxonomy. ment. Grice's maxims considered harmful Clearly, these explanations are similar in character; A misleading taxonomy unfortunately, as we will see below, speakers often pro- vide more or less information than is necessary, so the Several researchers have tried to implement Grice's generalization made by the maxim is not valid. maxims in some fashion (for example, [Gazdar 79, The other way these phenomena could be related Hirschberg 85]). This is not possible to do directly, is if the detailed, specific formal mechanisms for han- due to the vagueness of the maxims, so they typi- dling the two phenomena are similar. In fact, the cally have implemented something more reasonable, formal mechanisms proposed to handle them differ. and then claimed it was \Gricean". More often, re- Hirschberg describes them as different phenomena be- searchers have tried to use Grice's maxims to describe fore defining her mechanism for scalar implicature, and particular systems or phenomena (for example, [Dale Gazdar states [Gazdar 79, p. 59] that his mecha- and Reiter 95, Joshi et al. 84, Passonneau 95]). Be- nism for handling scalar implicatures does not gener- cause the maxims have the form of a taxonomy, they ate clausal implicatures, justifying his development of lead researchers to think that the maxims taxonomize a separate formal mechanism for clausal implicatures. the space of conversational implicatures in some use- At the very least, no rigorous connection to the maxim ful fashion. But using the maxims even in this way is is established, and it seems clear to me that there re- counter-productive, because they are much too vague, ally isn't one. So, while each phenomenon appears to and often overlap when applied to actual examples of be well-defined in its own right, there does not seem conversational implicature. They tend to lead to con- to be any clear similarity in the way they are actually fusion more than enlightenment. processed. For example, it is pointless to discuss (as Levinson There is a subtle but important clue to the gen- does [Levinson 83, p. 109]) whether a particular phe- esis of such an unhelpful taxonomy in Grice's origi- nomenon such as irony is based on the flouting of Rele- nal article [Grice 75]. Grice says that his categories vance or Quality. Irony is a phenomenon that fits quite are \echoing Kant" (p. 45). This clearly refers to comfortably into both notions. It flouts both at once, Kant's theory of categories, which classified declara- and perhaps Manner, too. The desire to decide which tive statements along four dimensions: Quantity, Qual- maxim irony flouts is based on the false impression that ity, Relation, and Modality. This makes it clear why there is some kind of significant difference between im- Grice's taxonomy does not fit the discourse phenomena plicatures that fit into one category and those that fit it was supposed to describe; it has been borrowed as a in the other. whole from a pre-linguistic, philosophical classification The maxims not only divide discourse phenomena up of statements! Taxonomies from one domain simply badly; they also group them together badly. Scalar and cannot be transferred wholesale to another and retain clausal quantity implicatures [Gazdar 79, Hirschberg any usefulness. It is interesting that this attribution 85] are a good example. These have both been de- has never been quoted, to my knowledge. scribed as subtypes of Quantity implicatures. But there does not seem to me to be any good reason to Trying to make use of a misleading believe that these are two subclasses of the same phe- taxonomy nomenon. Clausal implicature typically occurs when an embed- Despite their vagueness, the maxims are clearly true ded proposition is neither affirmed nor denied by the in some sense. This, coupled with their vagueness, full utterance. So the utterance of \If John sees me has allowed numerous researchers to read into them then he will tell Margaret" implicates that the speaker all sorts of specific true interpretations, rather than treating them as maxims, as Grice's name for them does not know whether John will see him. The stan- 1 dard explanation of this is that, based on the Cooper- suggests . As in the examples above, when we exam- ative Principle, if the speaker knew whether the first ine what actually exists in specific systems that are clause were true or false, he should have said so. claimed to fulfill one or more of the maxims, we find Scalar implicature, on the other hand, is based on much more specific mechanisms that apply to much the existance of sets of terms that have some salient more specific phenomena, and only bear a very ten- partial ordering in degree of informativeness. So the uous connection to the maxims. The clarity of these utterance of \Paul ate some of the eggs" implicates individual phenomena and rules, despite any remain- that the speaker does not know that Paul ate all of the ing controversies, is in sharp contrast to the haze of eggs. Again, the standard explanation of this relies on confusion surrounding the maxims. Given this, and Quantity, that the speaker should have said so if he 1Although Grice apparently did intend for them to be knew. applied rigorously. the fact that researchers often point out major prob- erate a conversational implicature? According to the lems with the maxims, it is difficult to understand the maxim of Quantity, a speaker generating clearly super- widespread, seemingly willful refusal to realize that the fluous information should cause the hearer to produce maxims simply are not correct. implicatures, as in the previous example. This phe- As one example of being \soft on Grice", Hirschberg nomenon clearly violates any direct interpretation of [Hirschberg 85] redefines Quality very narrowly, and Quantity. indicates that Quantity, Manner, and Relevance can- The truly surprising thing is that Dale and Reiter not really be defined precisely. Yet she then goes on discuss this total failure of Quantity in the paper, and to write logical formulae containing the maxims, as if yet do not describe it as a failure.