Credible debate equilibria

Abstract

Legislation is not an end in itself, but means to an end. Unfortunately, the technical relationship connecting any legislation to real consequences is rarely known for sure. In debate, legislators have an opportunity to persuade others of the relative value of particular bills, to influence the substance of the agenda, and to affect voting decisions. Since preferences over consequences are typically taken to be fixed, such persuasion etc. necessarily amounts to changing beliefs over the likely effects of various alternative bills. The extent to which debate can be effective in altering others' beliefs depends on how audiences interpret and assimilate any information speechmakers volunteer. This paper considers one plausible approach to credibility in debate. Debate is modeled as a cheap talk stage preceding an endogenous agenda setting game under incomplete information. In this framework, the issue can be formulated in terms of what constitutes an equilibrium. It is demonstrated that a fairly weak and intuitively plausible criterion of credibility effectively leads to there being little opportunity for credible transmission of information in debate.