Presupposition Projection and Accommodation

Projection concerns how the presuppositions of parts of a complex sentence survive in the whole, and accommodation is the hearer's adjustment of the context to admit a presupposition.

Definition

Projection is the inheritance of presuppositions by complex expressions from their parts; accommodation is the process by which a hearer adjusts the common ground to satisfy a presupposition that was not already established.

Scope

This topic covers the projection problem, the question of how to predict the presuppositions of a complex sentence from those of its constituents under operators like negation, conditionals, and connectives, and Karttunen's classification of expressions as plugs, holes, and filters. It covers dynamic accounts of projection in terms of context update, and Lewis's notion of accommodation, by which hearers quietly add a presupposed proposition to the conversational record when it was not already there.

Core questions

• How are the presuppositions of a complex sentence determined from those of its parts?
• Why do some operators block, let through, or conditionalize presuppositions?
• How does a context update account explain projection?
• What is accommodation, and when does it occur?

Key concepts

• projection problem
• plugs, holes, filters
• context-change potential
• common ground update
• accommodation
• local vs. global accommodation

Key theories

Plugs, holes, and filters (Karttunen)

Embedding expressions are classified by how they handle presuppositions: holes let them through, plugs block them, and filters (such as conditionals and connectives) pass them only under certain conditions.

Dynamic / context-change account (Heim)

Meanings are context-change potentials; presupposition projection follows from the order in which sentence parts update the context, deriving the filtering behaviour without stipulating it.

Accommodation (Lewis)

When a speaker presupposes something not yet in the common ground, hearers typically accommodate by adding it to the conversational score, so the utterance becomes acceptable.

History

Karttunen's early-1970s work identified the projection problem and the plugs-holes-filters typology. Lewis introduced accommodation through the metaphor of conversational scorekeeping in 1979, and Heim's dynamic context-change semantics in the early 1980s offered a unified account from which the filtering behaviour follows, shaping subsequent theories of presupposition.

Debates

Whether projection should be derived or stipulated

Whether the projection behaviour of connectives and operators must be lexically stipulated (as in some early accounts) or follows from a general dynamic semantics of context update, and whether dynamic accounts overgenerate.

Key figures

• Lauri Karttunen
• Irene Heim
• David Lewis
• Robert Stalnaker

Seminal works

• karttunen1973
• heim1983
• lewis1979

Frequently asked questions

What is presupposition accommodation?

It is the hearer's tacit acceptance of a presupposed proposition that was not already part of the common ground, as when 'I have to pick up my sister' leads the hearer to accept that the speaker has a sister even if this was not previously mentioned.