“Democracy is a commons, not a market.” A commons is an unregulated public resource—in the classic example, in Garrett Hardin’s essay “The Tragedy of the Commons” (1968), it is literally a commons, a public pasture on which anyone may graze his cattle. It is in the interest of each herdsman to graze as many of his own cattle as he can, since the resource is free, but too many cattle will result in overgrazing and the destruction of the pasture. So the pursuit of individual self-interest leads to a loss for everyone.

Caplan rejects the assumption that voters pay no attention to politics and have no real views. He thinks that voters do have views, and that they are, basically, prejudices. He calls these views “irrational,” because, once they are translated into policy, they make everyone worse off. People not only hold irrational views, he thinks; they like their irrational views.