 That this is not possible is illustrated by the oddity of the following two cases: It is not the case that Mary invited John or Bill, because she invited both or It is not the case that the prize is either in the attic or in the garden, because I know that it is in the garden. Since strong senses of or seem to be restricted to “unenclosed” uses for which an alternative explanation is available, Grice’s conclusion is that only  (25a)  should be taken as part of the semantic contribution of the sentence (what is said). The exclusive and ignorance inferences in  (25b)  and  (25c)  are merely pragmatic effects (conversational implicatures) which derive from interactions between a weak (truth-functional) interpretation of or with general principles of conversation.