Two of the monumental catastrophes of the twentieth century—Nazism and Communism—led to the slaughter of millions of human beings by their own governments, in the name of either ridding the world of the burden of “inferior” races or ridding the world of “exploiters” responsible for the poverty of the exploited. While each of these beliefs might have been testable hypotheses, their greatest political triumphs came as dogmas placed beyond the reach of evidence or logic.
