Full Idea
The most obvious test for presupposition would be this: if s generates the presupposition p, then an utterance of s would be infelicitous, unless p is taken for granted by participants in the conversation.
Gist of Idea
A presupposition is what makes an utterance sound wrong if it is not assumed?
Source
Ofra Magidor (Category Mistakes [2013], 5.3.1.1)
Book Reference
Magidor,Ofra: 'Category Mistakes' [OUP 2013], p.117
A Reaction
The principle of charity seems to be involved here - that we try to make people's utterances sound right, so we add in the presuppositions which would achieve that. The problem, she says, is that the infelicity may have other causes.