Full Idea
Grice drew attention to situations in which a person is justified in believing a proposition, which would nevertheless by an unreasonable thing for the person to say, in normal circumstances. I think he is right about disjunction and negated conjunctions.
Gist of Idea
A person can be justified in believing a proposition, though it is unreasonable to actually say it
Source
report of H. Paul Grice (Logic and Conversation [1975]) by Dorothy Edgington - Conditionals (Stanf) 2.4
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.8
A Reaction
Edgington considers Grice's ideas of implicature as of permanent value, especially as a clarification of 1950s ordinary language philosophy.
Related Idea
Idea 14274 Inferring conditionals from disjunctions or negated conjunctions gives support to truth-functionalism [Edgington]