Completing The Foundation : Norms, Coordination, and Privacy in Public

Why do privacy scholars have inconsistent attitudes about social norms? They mostly agree that social norms play a key role in ensuring adequate informational privacy, particularly “privacy in public.” But they ignore norms when making concrete proposals about how to preserve privacy. Advocates of Notice and Choice seek to empower individuals to make informed choices. Others seek to protect the privacy through privacy by design, proposals to make businesses and governments trustworthy collectors and users of information, or consumer protection laws that limit the ability to know and use information. None of the proposals assigns norms a key role and builds on that foundation. Why not? Our explanation is that the foundation is incomplete. Patterns of scholarship have multiple explanations, but an incomplete foundation is a key factor in the case of privacy in public. You cannot build on what will not bear the weight. The missing foundational element is common knowledge. Common knowledge is the recursive belief state of two or more parties knowing, knowing they know, knowing they know they know, and so on potentially ad infinitum. Appeals to common knowledge in the privacy literature are nonexistent. That lack of attention is of a piece with a general tendency to overlook common knowledge. Apart from game theory, philosophy, and sociology, common knowledge has had little visibility - even though, as an influential article notes, “much of social life is affected by common-knowledge generators, . . . [and] an acknowledgement of the role of common knowledge in enabling coordination can unify and explain a variety of seemingly unrelated and puzzling phenomena.” Unifying and explaining is our goal as we show how to use norms to preserve informational privacy in the face of pervasive surveillance. Pervasive surveillance subverts the power of social roles to generate common knowledge thereby undermines coordination under informational norms thus reducing privacy in public and threatening self-realization. An essential step in preserving privacy is ensuring that social roles generate common knowledge that facilitates coordination under informational-privacy-creating social norms. We show how to take that step