Recall that entailments are taken to be part of the meaning derived via Semantics, whereas implicatures require Pragmatics. Presupposition falls somewhere in between. Presupposed content is not typically thought of as part of the main point of an utterance (what was said) but the meaning can be recovered without recourse to complex pragmatic reasoning. This section covers the following:
When we interpret a statement, we must understand what proposition is being asserted. Accompanying that primary proposition p are other propositions that can be relevant to the interpretation of p. This can arise not just with statements, but also with other types of utterances like questions and orders.
Presuppositions must be "in place" for the utterance to make sense. For example, (1) has both presupposed meaning and asserted meaning:
(1) John regrets that he failed the exam.
Presupposition: John failed the exam.
Assertion: John regrets it.
Likewise, when we interpret a question, we must understand the proposition being directly interrogated as well as any additional propositions relevant to it being a valid question. See example (2):
(2) Has the guy in the checkered suit left?
Presupposition: There was a guy in a checkered suit.
Question: Did he leave?
Lastly, in an imperative like the one in (3), there is again a distinction between the presupposed meaning and the actual order.
(3) Hand me the yellow book!
Presupposition: There is a (unique) yellow book.
Order: Hand it to me!
Green (1996) observes that presuppositions can be described both semantically and pragmatically. Semantically, presuppositions are propositions without which the truth of an utterance cannot be evaluated. Pragmatically, presuppositions are propositions whose truth is taken for granted in the utterance of a linguistic expression. The former is about truth; the latter about use.
Certain sentences presuppose the truth of a related sentence. Compare (4) and (5).
(4) Kim is happy that she got into the University of Edinburgh.
(5) Kim told me that she got into the University of Edinburgh.
The presupposition in (4) is a Factive Presupposition; it presupposes a fact. Another kind of presupposition involves the status of whether or not something exists. Existential Presuppositions presuppose the existence of a referent when a definite noun phrase has been used. The sentence in (6) presupposes p "that there is a cat [in the relevant context]", while the sentence in (7) does not.
(6) The cat can watch birds outside all day.
(7) A cat can watch birds ouside all day.
The remaining sections consider some key properties of presuppositions: how they differ from entailments, how they arise, and what happens when they are violated.
To go on to section 3.2 "Properties and diagnostics of presuppositions", click here.