Common Knowledge and Cheap Talk in Democratic Discourse and Law

This commentary illuminates key aspects of Shiffrin’s view by appeal to concrete examples and notions from game theory. It underscores the role of law as a means for the public communication of moral commitments by invoking the idea of common knowledge. Our commitments must be known to be shared, that knowledge itself must be known to be shared, and so on ad infinitum. This offers a perspective on the importance of common law from a democratic framework: common law can be seen as a mechanism for generating common knowledge about disputes and their resolution. The commentary invokes another game-theoretic notion, that of the contrast between cheap talk and costly signaling, to illuminate Shiffrin’s discussion of constitutional balancing. Where the interests of speaker and addressee are not aligned, cheap talk lacks credibility, and this is something to which courts need to be sensitive in balancing state and constitutional interests.