Logic & Philosophy of Science Colloquium

Michael Glanzberg
Massachusetts Institute of Technology

"Presuppositions, Truth Values, and Expressing Propositions"

One of the familiar parts of the philosopher's toolkit is the idea that some class of sentences fail to express propositions in certain contexts. This tool has been applied to a wide range of issues, from problems in philosophical logic such as vagueness, semantic paradox, and indicative conditionals, to expressivism in moral theory. Traditionally, the notion of failing to express a proposition has been linked to two other important notions: the pragmatic notion of presupposition, and truth value. A common traditional picture is that when an assertion fails to express a proposition in some context, it is because of presupposition failure in the context. Presupposition failure, in turn, is indicated by lack of truth value. However, more recent work has significantly complicated the traditional picture. Research in philosophy of language and linguistics has shown the notion of presupposition to be rich and diverse, in ways that obscure its relation to truth-value judgments and the intuitive notion of expressing a proposition in a context.

In this essay, I shall investigate the relation between the philosophical notion of expressing a proposition and the linguistic notion of presupposition. In doing so, I shall pursue three linked goals. First, I shall offer an analysis of the philosophical notion of failing to express a proposition. Second, I shall offer an account of how failure to express a proposition may be recognized in natural language, by way of some discourse-based diagnostics which are more robust and reliable than simple truth-value judgments. Third, I shall attempt to document what gives rise to the phenomenon of expression failure. This third part of the essay will involved some detailed investigation into presupposition. I shall show that some presupposition failures lead to expression failure, but some do not. I shall go on to offer an analysis of elementary presuppositions which explains why presuppositions fall into these two categories. This will involve close examination of some important cases of presupposition: clefts, factive verbs, demonstratives, and presuppositions generated by conventional implicatures such as those of 'too', and 'even'. I shall conclude the third part of the essay with some speculation about the relation of conventional implicature to presupposition.

Much of the work in this essay is thus dedicated to detailed investigation presupposition, which is one of the central aspects of context dependence. But in shedding light on the connection between presupposition and the notion of failing to express a proposition, I hope to add some substance to a sometimes-contentious part of the philosopher's toolkit as well.

Friday, April 4, 2003
SST 777
3 pm

Refreshments will be served