A conversation is invariably shaped by what its participants decide not to say. To avoid destructive conflicts, we suppress controversial themes. In Cambridge, Massachusetts, old friends shun the subject of Israel in order to keep old friendships intact. Burying a divisive issue, of course, can be viewed censoriously – as evasiveness rather than diplomacy. But conflict-shyness is not merely craven: it can serve positive goals. By tying our tongues about a sensitive question, we can secure forms of cooperation and fellowship otherwise beyond reach.

Strategic self-censorship occurs in a variety of settings, from international summits to midnight trysts – including perhaps the limiting case of amnesia. In collective life, unmentionables abound. Within every group, speaking about tabooed subjects will provoke general consternation and embarrassment. After all, no one should wash his dirty linen in public. At faculty meetings, even garrulous professors will not prattle interminably about their alcohol problems or marital relations. Such universally appreciated uncommunicativeness can be easily explained. For one thing, no group's information-processing capacity is infinite. People cannot talk about everything at once; life is short; to avoid cognitive overload, different groups focus on different topics at different times.

Other reasons for sealing one's lips are less general and more pertinent to democratic theory. Sometimes an issue appears “unspeakable” because open airing would mortally offend prominent individuals or subgroups and permanently injure the cooperative spirit of the organization.