On Testing for Conversational Implicature

J. D. Sadock, "On testing for Conversational Implicature", in Kasher, "Implicature", investigates three criteria
for deciding whether a certain implication is an
entailment or a conversational implicature: cancelability
and non-detachabilty (which were proposed by Grice) and
reinforceability. He thinks that no criterion alone, and
no combinations of the criteria is a necessary property
of conversational implicatures.