Disimplicature

Speranza

Grice argues for an analysis of ‘therefore’ as presupposition trigger against the more standard conventional implicature story originally put forward by Grice (1975). 

Grice proposes that we model the relevant presupposition as “testing” the context in a way that is similar to how, according to Veltman (1996), epistemic ‘must’ tests the context. But whereas the presupposition analysis is plausible for ‘therefore’, ‘must’ is not plausibly a presupposition trigger. Moreover, whereas ‘must’ can naturally occur under a supposition, the same is not true for ‘therefore’. In the light of these differences, I suggest we distinguish between different sorts of tests on the basis of the mechanisms whereby these expressions test the context (whether through a presupposition or through their core content) and on the basis of whether they can operate only on categorical contexts or on both categorical and hypothetical contexts.