enduring characteristics of the· human condition. My main goal in this book has been to understand those characteristics and to see what might be done about them. To this end, I have ventured a unified treatment of three social phenomena: conformity, cascade and group polarization. All of these are produced, first, by the information contained in the acts and statements of others and, second, by the social force imposed by those acts and statements.

When groups go to extremes, the reason often lies in the influences that people place on one another. This is true for feuding families, religious organizations, sports fans, and investment clubs· it is true for revolutionaries and terrorists; it is true for listserves, gangs, and cults; it is true for political parties, legislatures, courts, regulatory agencies, and even nations. When group polarization is involved, people tend to discuss information that everyone already has and tend not to share information held by only one or a few group members. This is a serious loss. If groups go to extremes, they should do so for good reasons, not simply because people's preexisting tendencies are reinforced and amplified as a result of internal discussions.

Of course, conformity often makes a great deal of sense. If we don't have a lot of independent information, we might do best if we do what other people do. The problem with conformity is that it deprives society of information that it needs. I have emphasized the same problem with social cascades, in which people follow others and fail to disclose what they actually know. As a result of cascades, both individuals and groups can blunder badly. When grave injustice exists, it often persists only because most people have a false impression of what other people think. They silence themselves, thinking that others must be right or simply wanting to avoid social disapproval. The tragedy is that blunders and injustice could be avoided if only people would speak out. Dictators and tyrants, large and small, are usually naked emperors.

The general lesson is clear. Organizations and nations are far more likely to prosper if they welcome dissent and promote openness.


Well-functioning societies benefit from a wide range of views; their citizens do not live in gated communities or echo chambers. The fantastic economic success of the United States owes everything to a culture of open information. Indeed, economic markets themselves embody norms of openness, ensuring success for those who innovate (and innovation is itself a form of dissent). Free speech and open dissent are the siblings of free markets. To the extent that the United States has done well in peace as well as war, it owes its greatest debt to principles of free expression. But democracies, no less than other systems, frequently create the majority tyranny that Mill deplored, simply because social pressures impose burdens on dissenters.

We have seen that an appreciation of social influences casts light on the expressive function of law. Merely by virtue of what it says, law often affects human behavior. Bans on smoking in public and on sexual harassment are cases in point. Law's effectiveness lies in its power to give a signal about what it is right to do, and also to provide information about what other people think that it is right to do. Because people care about the reactions of others, law's expressive function will be heightened if violations are visible. With an understanding of social influences, we can make some predictions about when law is likely to be effective merely by virtue of what it says-and also about when law will be ineffective unless it is accompanied by a lot of enforcement activity. We can also see why dictatorships, far more than democracies, need the police, and why they have to depend on the inculcation of terror.

Many of the Constitution's rights and institutions reduce the risk of harmful consequences from conformity, cascades, and group polarization. Freedom of speech is the simplest example, providing a check on bad cascades and unjustified extremism. At a minimum, a system of free expression forbids government from restricting any point of view. We have also seen the importance of ensuring that people are exposed to a range of positions and do not self-select into narrow communities of their own devising. By creating public