Dummett on Grice

Speranza

Heck writes:

"The claim that speech is rational thus amounts, in the first instance, to this: Speech is intentional under propositional descriptions, such as “saying that p”. Let me emphasize that I make this claim not on the basis of a priori reflection but on the basis of empirical observation. That is not to say that it is not a conceptual truth (if such there are) that speech is intentional under propositional descriptions: In fact, I
doubt that we would be prepared to call anything ‘speech’ or ‘the use of language’
that was not intentional under propositional descriptions. This seems also to be the point of Dummett’s ‘barely intelligible fantasy’ (Dummett, 1991:91). But I doubt it matters,
for present purposes, whether the claim that human speech is propositionally rational,
as I shall put it, is a conceptual or merely an empirical truth.
That speech is propositionally rational is obvious, or so it seems to me, so I shall
not argue for the claim directly. What I am going to do, though, is argue that
the propositional rationality of speech is what ultimately explains the phenomenon
Grice called ‘conversational’ implicature."