Cass Sunstein examines the phenomenon of enclave extremism--the tendency of people to harden their political positions when they interact mainly with others of like mind. (Thanks to A&L.)

[O]n many issues, most of us are really not sure what we think. Our lack of certainty inclines us toward the middle. Outside of enclaves, moderation is the usual path. Now imagine that people find themselves in enclaves in which they exclusively hear from others who think as they do. As a result, their confidence typically grows, and they become more extreme in their beliefs. Corroboration, in short, reduces tentativeness, and an increase in confidence produces extremism. Enclave extremism is particularly likely to occur on the Internet because people can so easily find niches of like-minded types — and discover that their own tentative view is shared by others.

It would be foolish to say, from the mere fact of extreme movements, that people have moved in the wrong direction. After all, the more extreme tendency might be better rather than worse. Increased extremism, fed by discussions among like-minded people, has helped fuel many movements of great value — including, for example, the civil-rights movement, the antislavery movement, the antigenocide movement, the attack on communism in Eastern Europe, and the movement for gender equality. A special advantage of Internet enclaves is that they promote the development of positions that would otherwise be invisible, silenced, or squelched in general debate. Even if enclave extremism is at work — perhaps because enclave extremism is at work — discussions among like-minded people can provide a wide range of social benefits, not least because they greatly enrich the social "argument pool." The Internet can be extremely valuable here.

But there is also a serious danger, which is that people will move to positions that lack merit but are predictable consequences of the particular circumstances of their self-sorting. And it is impossible to say whether those who sort themselves into enclaves of like-minded people will move in a direction that is desirable for society at large, or even for the members of each enclave. It is easy to think of examples to the contrary — the rise of Nazism, terrorism, and cults of various sorts. There is a general risk that those who flock together, on the Internet or elsewhere, will end up both confident and wrong, simply because they have not been sufficiently exposed to counterarguments. They may even think of their fellow citizens as opponents or adversaries in some kind of "war."

Gosh. Could that really happen?