A presupposition is, in linguistic terminology, the name given to an implied fact that needs to be assumed before a given sentence can be accepted as true. Understanding presuppositions is important in the world of NLP, indeed, NLP itself has a list of about 20 presuppositions. Here is a list of the types of linguistic presupposition:
Existence. The presence of a noun presupposes the existence of the object or person to which the noun refers.
"My car has broken down" implies that I have a car.
Possibility/necessity. The use of the words can, could, should, won't, can't, must, needs to, may, etc. The technical term for these is modal operator.
Cause and effect. Any use of implication, if...then and the words so, because presupposes a causal link between the two halves of the sentence.
Complex equivalence. The verb to be, or the word means, presupposes that two things or concepts are in some way the same. See the writeup e-prime for an attempt to purge complex equivalence presuppositions from our language.
Awareness. This type of presupposition involves words about our senses, for example:
"... as you can see"
Time. Words about time, such as soon, since, before, yet, earlier, later etc. and verb tenses presuppose a timing aspect of what is going on, as can the word "stop", indicating that an action is in the past since it is no longer taking place.
Adverb or adjective. Adverbs and adjectives presuppose that the action or object has the particular property described.
Inclusive or/exclusive or. Use of the word "or" presupposes choosing between possibilities. The context defines whether this is a choice of one possibility (exclusive or) or any number of possibilities provided at least one (inclusive or).
Ordinal. Words such as first, second, last, next, previous, etc. presuppose that there is some kind of ordered sequence.
Presuppositions are a part of everyday language. An understanding of presuppositions is useful from an NLP perspective in several ways:
Presuppositions form a part of the Milton Model, which is a collection of language constructs to induce trance. They work by giving the conscious mind more things to think about at a given point in time. As the conscious mind can only process 7 ±2 things, this goes towards overloading the conscious mind and inducing trance.
Presuppositions can also be used in the opposite way, to shock the listener, challenging their world model, and wake them up. Here, what is presupposed can be complete nonsense, which would nowhere near have the same effect if stated as a fact.
We use presuppositions in negotiation, especially in areas like sales:
"Our excellent course will satisfy personal development needs that you have no idea of, yet."