  It is standardly accepted that these sentences generate, respectively, the presuppositions that France has a king; that George used to smoke; and that someone murdered Jack. What precisely this amounts to is a matter of controversy in the theory of presupposition, but as a first pass we can say that when these sentences are uttered in conversation, the presupposed material is not the main point of the speaker’s assertion and that participants in the conversation are expected to already have accepted it. Moreover, when such sentences are uttered in contexts where speakers do not already accept the presupposition, the utterance suffers from presupposition failure, and is consequently infelicitous. For example, in current context, an utterance of (26) seems infelicitous because we all know France does not have a king, and an utterance of (28) is infelicitous in a context where it was not  already commonly believed that Jack was  murdered.[26]