Modal Adverbs as Negotiation Chips

A basic assumption is that modal adjectives such as possible, probable, certain,
and evident, are synonymous with modal adverbs such as possibly, probably, certainly and evidently. In this paper we challenge this view, provide a uniform formal account of modal adverbs and modal adjectives, and discuss the role of modal adverbs in discourse. We present an expanded context update theory that includes an intermediate mechanism, Negotiation Zone, in addition to the common ground, within which are placed asserted propositions together with degrees of strength. Modal adverbs modify this degree of strength, representing the degree of belief of the speaker in her asserted proposition. The degree of belief functions as one of the sources of evidence that play a role in the hearer's decision process, and affects the hearer's considerations for accepting or rejecting the speaker's assertion.