 While irony often involves saying something obviously false, it need not have been obvious to Carla in  (2)  that Don believed the weather was unlovely. She may have had no independent source of information about his weather. Don would also have made a suitable contribution to the conversation if he had meant and believed that the weather is lovely. So Determinacy is unsatisfied in irony when the speaker could have been speaking literally, believing what was said (W. Davis 1998: §3.3; see even Grice 1978: 53).