Robert Proctor doesn't think ignorance is bliss. He thinks that what you don't know can hurt you. And that there's more ignorance around than there used to be, and that its purveyors have gotten much better at filling our heads with nonsense.

Proctor, a professor of the history of science at Stanford, is one of the world's leading experts in agnotology, a neologism signifying the study of the cultural production of ignorance. It's a rich field, especially today when whole industries devote themselves to sowing public misinformation and doubt about their products and activities.

The tobacco industry was a pioneer at this. Its goal was to erode public acceptance of the scientifically proven links between smoking and disease: In the words of an internal 1969 memo legal opponents extracted from Brown & Williamson's files, "Doubt is our product." Big Tobacco's method should not be to debunk the evidence, the memo's author wrote, but to establish a "controversy."

When this sort of manipulation of information is done for profit, or to confound the development of beneficial public policy, it becomes a threat to health and to democratic society. Big Tobacco's program has been carefully studied by the sugar industry, which has become a major target of public health advocates.