The ideal of totally personalized media (on the Internet, and elsewhere, too) is increasingly popular. Read, see and listen to only what you really want: What could possibly be wrong with that? If we lived by bread alone, "absolutely nothing" just might be the answer. But we don’t. So argues constitutional scholar Cass Sunstein in Republic.com. Above all, we live by a vast cooperative venture called civilization, organized through systems of law, in which we are citizens before we are consumers. No civilization, no Internet. It’s that simple.

The marketplace, celebrated in the notion of "consumer sovereignty," lives by satisfying individual tastes, but democracy and "political sovereignty" live by deliberation, which doesn’t take tastes as fixed or given. Social theorist Jon Elster uses the parable of the fox and the sour grapes to point out that preferences may reflect availability as much as the reverse. Thus, the need to go beyond consumer sovereignty. Sunstein grounds his arguments in the functioning of classic public forums (pre-automobile streets and parks) and general interest intermediaries (newspapers, broadcast TV, etc.), as well as Constitutional law, but spends most of his time applying these and related insights to the Internet.

He appreciates the incredible diversity of topics and viewpoints found there, but applying the standards of political sovereignty, he explores the downside, particularly the fragmentation and polarization that could cripple the possibility of constructive democratic action. The dangers he cites should be familiar to anyone who’s been on a mailing list, or visited a few political sites. Viewpoint isolation tends to breed extremism, driving out moderate positions and arguments. The short-term satisfactions involved come at the cost of long-term damage to the political process, costs not internalized in typical online forums.

After his penetrating analysis, Sunstein’s suggested remedies are surprisingly weak, but still should stimulate much-needed debate.