Five defining characteristics of stupidity, it seems to me, are readily apparent. First, is sheer ignorance: Ignorance of critical facts about important events in the news, and ignorance of how our government functions and who's in charge. Second, is negligence: The disinclination to seek reliable sources of information about important news events. Third, is wooden-headedness, as the historian Barbara Tuchman defined it: The inclination to believe what we want to believe regardless of the facts. Fourth, is shortsightedness: The support of public policies that are mutually contradictory, or contrary to the country's long-term interests. Fifth, and finally, is a broad category I call bone-headedness, for want of a better name: The susceptibility to meaningless phrases, stereotypes, irrational biases, and simplistic diagnoses and solutions that play on our hopes and fears.
--Rick Shenkman, "How Ignorant Are We?"