Vagueness of Language: Indeterminacy under Two-Dimensional State-Uncertainty

Abstract We study indeterminacy of indicative meanings (disagreements about meanings of messages among players), a kind of language vagueness examined in Blume and Board (2013. “Language Barriers.” Econometrica 81 (2): 781–812). They, using a cheap talk model in which the state-distribution and the players’ language competence were ex-ante uncertain, demonstrated that this vagueness occurs as an equilibrium language. We expand the work of Blume and Board by using a model between an uninformed decision maker and an informed agent in which the state-distribution and the state are both ex-ante uncertain. We show that this two-dimensional uncertainty also leads to indeterminacy of indicative meanings, that is, to a set of conditions in which an agent with different perceptions of the state-distribution intentionally uses the same symbol for the different extents of information on the state. The vagueness, contrary to common expectations, can actually lead to welfare improvement.