Scalar quantity implicatures and the interpretation of modality

This paper argues that scalar quantity implicatures do not work across the modal domain as a whole, as has traditionally been assumed in the literature, but that deontic modal expressions pose a specific problem for the mechanism of scalar implicatures. It is argued that the problems with deontic modality are due to the fact that expressions of permission and obligation are different on two dimensions: they do not just express weaker and stronger commitment to desirability on the part of some authority, but they also carry different presuppositions about the willingness of the modal agent (the person who is allowed or obliged to do something) to carry out the action in question. The consequence of this difference is that the two types, unlike their epistemic counterparts, do not form a perfect scale. They differ in more respects than just modal strength, and this disrupts the implicature mechanism that works well for the weaker and stronger degrees of epistemic modality.