Two Kinds of Conversational Implicatures

This paper discusses the underexplored distinction between additive and substitutional conversational implicatures. The focus of the paper is on the question of how to define the distinction. The paper argues that existing characterizations of the distinction classify some implicatures as substitutional that are in an intuitive sense additive. It provides a new definition that captures this sense, and it explores how the new definition differs from previous characterizations. The paper also takes a look at the debate on lying and misleading, in which the distinction between additive and substitutional implicatures has recently attracted some attention as a heuristic for which implicatures constitute lies. It argues that the new definition of the additive-substitutional distinction is useful for this purpose, since it provides a better heuristic than previous characterizations.