 The ratio of positive cognitive effects to processing cost is zero when there are no positive cognitive effects at all. Given the definition of contextual implication, any proposition that is part of the cognitive context has no contextual implications. So both Maximal and Optimal Relevance seem to imply that speakers cannot mean or implicate anything already known, and must mean something else. Gerrig (1987: 718) and McCawley (1987: 724) find this implausible. If A and B are walking in torrential rain, A might well say “It is raining really hard”, stating the obvious, and B might respond “There is indeed some rain coming down”, engaging in understatement and implicating exactly what A said.