Presuppositions are one variety of commitment that speakers make in speech acts. The long-running effort to understand how they relate to other speaker commitments in conversation has explored both the role presuppositions play in determining communicative naturalness or anomaly and also patterns of projection (inheritance) of semantically embedded expressions’ presuppositions that differ from semantic composition of the expressions’ primary proffered content.

Similarities in behavior of presuppositions both to other speaker commitments such as conventional implicatures and to non-commitments such as conversational implicatures have at times impeded the investigation, which has been reinvigorated in recent years by new tools for describing the role of utterance context as an influence on projection of semantically embedded expressions’ speaker commitments.

The talk examines these issues, assesses the use of widely used presupposition tests such as the family of sentences test, sharpens the question whether presuppositions need to be semantically differentiated from proffered content by grammatical stipulation, and clarifies some differences between the several varieties of commitment that speakers undertake in performing speech acts.