[Full paper in pdf]
Abstract: Sentence (1) implies that the speaker does not have a sister:
(1) John believes that I have a sister.
(2) Alternative: John knows that I have a sister.
(3) Predicted inference: it is not common belief that the speaker has a sister.
(4) Actual inference: the speaker does not have a sister.
Following Heim (1991) - see also 2006 works by Percus and Sauerland - this inference might follow from the comparison of (1) to (2). However, such an analysis would only predict a very weak implicature: it is not common belief that the speaker has a sister. We propose to strengthen this prediction by two means. First, we rely on a precise understanding of the modern stalnakerian view of presuppositions and common ground (Stalnaker, 1998, 2002; von Fintel, 2000; Schlenker, 2006). Second, we argue that this inference depends on contextual factors. More precisely, we show that the Competence Assumption (see van Rooij and Schultz, 2004 and Sauerland, 2004) necessary to obtain secondary scalar implicatures can be successfully supplied with an Authority Assumption. We justify this additional assumption on independent empirical grounds. Finally, we present how our proposal applies to a wide variety of inferences with fine variations governed by 1) contextual differences and 2) specific properties of the presupposition triggers involved.