Presuppositions and Pronouns - Nijmegen Centre for Semantics

Presupposition 11
judgment of the facts is based upon the presupposition that they are
true; such presuppositions are unwise.
This may not seem to be very instructive, yet it is useful to be reminded that
presupposition is a deverbal noun, and that one speaks of presuppositions in
order to characterize not sentences or words but people and what they do.
Presupposition, according to Longman's dictionary, is either the action of
presupposing or its object. But what does it mean to presuppose something
pre-sup-pose pre'sup«pose /,pri:ss'psuz/ /,pri:s9'p9oz/ v [T1, [Tl, 5] 1 to suppose or take to be true
without trying to find out: A scientist never presupposes the truth of
an unproved fact 2 to be necessary as something that comes before
(something else) according to reason: A child presupposes a mother.
I An honour given to a person presupposes that he has earned it.
Now, although I hold Longman's dictionary in high esteem, it seems to me
that the second sense listed here is marginal at best. A child doesn't
presupposes a mother any more than a sentence presupposes a sentence. Be
that as it may, it is evidently the first meaning that is the primary one, and it
says that to presuppose something is to take it for granted. Again,
presupposing is something people do, and it is not necessarily verbal
behaviour, although it may be that it is typically expressed by linguistic
means.
This folk concept of presupposition is the basis for the theory that I present
in this book. The theory has its roots in a triad of papers by Stalnaker
published in the first half of the seventies (i.e. Stalnaker 1970, 1973, and
1974). In keeping with the layman's view, Stalnaker's starting point is that
presupposition is a 'propositional 'prepositional attitude', which is to be understood in
behaviourial terms:
A speaker presupposes that P at a given moment in a conversation
just in case he is disposed to act, in his linguistic behavior, as if he
takes the truth of P for granted, and as if he assumes that his
audience recognizes that he is doing so. (Stalnaker 1973: 448)
To presuppose something is like making a promise. If I promise my daughter
to buy her an ice cream, it is completely irrelevant what my actual beliefs and
intentions are: I made a promise regardless whether I intended to keep it or
not. Likewise, a speaker who presupposes something incurs a commitment
(to use Hamblin's expression) regardless whether he really believes what he
presupposes. To be sure, presuppositions are normally believed to be true,
but belief is not a prerequisite for presupposition.
Presupposition is the dual of assertion, and if the former is a prepositional
propositional
attitude, then so is the latter, and in the same sense. Like presupposition,
assertion implies commitment, not true belief. If a story teller asserts that the