Privacy issues arise, according to the traditional analysis, when computers are used to capture and circulate individually identifiable information. Unfortunately, this theory leads to intractable political controversies because it only offers two extreme options: complete identification and complete anonymity. It is well known that new cryptographic protocols provide a complicated space of options between these two extremes. Before we can make reasoned political and technical choices about the adoption of these technologies, however, we need a much fuller understanding of the "natural history" of identity in face-to-face and computer-mediated interactions as they already exist. In this talk, I will sketch some of the cognitive and institutional aspects of identity. Then I will apply this analysis to various questions of economics and Internet architecture.