Interpreting Don's utterance as conveying the opposite of its literal content treats the implicature as doing work that direct assertion could do more clearly.

Grice (1975: 30) recognized that his maxims may “clash”. When they do, there is no way to determine what is required for conformity to the Cooperative Principle. In the case of irony, for example, Manner clashes with Quality. When Don said “The weather’s lovely”, we cannot interpret him as meaning what he said because on that interpretation he would be violating Quality. But we cannot interpret him as meaning the opposite because then he would be violating Manner (Wilson & Sperber 2012: 18–9