Projection is widely used as a diagnostic for presupposition, but many expression types yield projection even though they do not have standard properties of presupposition, for example appositives, expressives, and honorifics (Potts 2005). While it is possible to analyze projection piecemeal, clearly a unitary explanation is to be preferred. Yet we show that standard explanations of projective behavior (common ground based theories, anaphoric theories, and multi-dimensional theories) do not extend to the full range of triggers. Instead, we propose an alternative explanation based on the following claim: Meanings project IFF they are not at-issue, where at-issueness is defined in terms of the Roberts' (1995) discourse theory. Thus, and despite their apparent heterogeneity, projective meaning triggers emerge as a natural class on the basis of the not at-issue status of their projective inference.

Projective contents, which include presuppositional inferences and Potts's (2005) conventional implicatures, are contents that may project when a construction is embedded, as standardly identified by the FAMILY-OF-SENTENCES diagnostic (e.g. Chierchia & McConnell-Ginet 1990). This article establishes distinctions among projective contents on the basis of a series of diagnostics, including a variant of the family-of-sentences diagnostic, that can be applied with linguistically untrained consultants in the field and the laboratory. These diagnostics are intended to serve as part of a toolkit for exploring projective contents across languages, thus allowing generalizations to be examined and validated crosslinguistically. We apply the diagnostics in two languages, focusing on Paraguayan Guaraní (Tupí-Guaraní), and comparing the results to those for English. Our study of Paraguayan Guaraní is the first systematic exploration of projective content in a language other than English. Based on the application of our diagnostics to a wide range of constructions, four subclasses of projective contents emerge. The resulting taxonomy of projective content has strong implications for contemporary theories of projection (e.g. Karttunen 1974, Heim 1983, van der Sandt 1992, Potts 2005, Schlenker 2009), which were developed for the projective properties of particular subclasses and fail to generalize to the full set of projective contents.*

This article deals with projection in factive sentences. The article first challenges standard assumptions by presenting a series of detailed observations about the interpretations of factive sentences in context, showing that what implication projects, if any, is quite variable and that projection is tightly constrained by prosodic and contextual information about the alternatives under consideration. The article then proposes an account which accommodates the variability of the data and sensitivity to contextual alternatives. The account is formulated within a modified version of Roberts 1996/2012 question-based model of discourse.

Projection is widely used as a diagnostic for presupposition, but many expression types yield projection even though they do not have standard properties of presupposition, for example appositives, expressives, and honorifics (Potts 2005). While it is possible to analyze projection piecemeal, clearly a unitary explanation is to be preferred. Yet we show that standard explanations of projective behavior (common ground based theories, anaphoric theories, and multi-dimensional theories) do not extend to the full range of triggers. Instead, we propose an alternative explanation based on the following claim: Meanings project IFF they are not at-issue, where at-issueness is defined in terms of the Roberts' (1995) discourse theory. Thus, and despite their apparent heterogeneity, projective meaning triggers emerge as a natural class on the basis of the not at-issue status of their projective inference.

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