K. draws a distinction between logical presupposition (defined as follows: a sentence S logically presupposes a sentence S' in case S logically implies S' and the negation of S, -S, also logically implies S'; i.e. the truth of S' is a necessary condition on the truth or falsity of S) and pragmatic presupposition (defined as follows: an utterance of a sentence pragmatically presupposes that its context is appropriate; i.e. contextual appropriateness conditions are pragmatic presuppositions).