According to H. P. Grice, the intelligibility of the conversation is ruled by “a rough general principle which participants will be expected (ceteris paribus) to observe”, namely:
‘Make your conversational contribution such as is required, at the stage at which it occurs, by the accepted purpose or direction of the talk exchange in which you are engaged’. One might label this the Cooperative Principle. (1975, p. 45; capitalized in the text).
This “Principle of Cooperation”, is specified under four forms, “Quantity, Quality, Relationship and Manner” (ibid.).
— Quantity: “I expect your contribution to be neither more nor less than is required” (ibid.).
— Quality: “I expect your contribution to be genuine and not spurious” (ibid.). This can be compared to the requirement of accuracy mentioned in the pragma-dialectical rule 8; the same concern is also found in Hedge’s Rule 1 “For an honorable controversy”, S. Rules.
— Relation: “I expect a partner’s contribution to be appropriate to immediate needs at each stage of the transaction” (ibid.). This concerns in particular the relevance of the turn in relation to the present topic of dialogue and action. Grice recognizes the difficulty of identifying what is relevant in an exchange. The pragma-dialectical “Relevance rule” deals with this same requirement (van Eemeren, Grootendorst (2004, p. 192). S. Relevance; Rules.
— Manner: “I expect a partner to make it clear what contribution he is making” (ibid.). This entry can cover the refusal of the obscurity of expression and action; of ambiguity (the first of the Aristotelian fallacies); of the unnecessary prolixity, corresponding to the fallacy of verbiage.
Grice holds that his principles capture the rational character of conversation:
One of my avowed aims is to see talking as a special case or variety of purposive, indeed rational behavior. (Id., p. 47)
as well as its reasonable character: Respecting these principles is not merely “something that all or most do IN FACT follow, but as something that it is REASONABLE for us to follow, that we should not abandon” (id., p. 48; capitalized in the text).
These four principles can be compared with those advanced by normative theories of argument, S. Rules.
A statement violating Grice’s principles is not eliminated as fallacious, but is understood as an indirect speech act. When a participant notes that something is not in conformity with a conversational rule, the reaction is not to accuse the partner of making an irrelevant or irrational contribution, but to engage in an interpretive process to identify why he or she has flouted the conversational rule. The analysis of fallacies reverts to this interpretive orientation whenever it adds to its logic pragmatic considerations taking into account the contextual conditions of the exchange.
In an argumentative situation, the concept of cooperation is a strategic issue redefined by the participants, who are not necessarily willing to cooperate, for example in their own refutation. There is nothing scandalous or irrational about this, insofar as partners are aware of being in such an intentionally opaque context, S. Politeness. Rational, reasonable, as well as honorable rules for discussion are intended to reintroduce or strengthen cooperation in such antagonistic contexts.