Crisis periods abound in history. But "even in the darkest of times we have the right to expect some illumination" wrote the political philosopher Hannah Arendt. She spoke from a keen, personal interest in dark times, for Arendt was a Jewish intellectual who fled from Hitler's Germany. But on whom does a society depend for the illumination that she demanded? The answer, increasingly, is—on the intellectuals.

The role of the 20th-century intellectual has become accepted and defined as that of an adversary—providing dissent when politics cease to mesh with ethics and freedom. In the 1960's, American intellectuals led opposition to the Viet Nam War, while their counterparts in the Soviet Union were galvanized into action by the 1966 Siniavsky and Daniel trial. (Their "crime" was publishing their books abroad.) Particularly in "dark times" or times of repression, intellectuals are called upon to be, as Karl Mannheim said, "watchmen in what otherwise would be a pitch-black night." And in recent times they have fulfilled that role.

Alexander Solzhenitsyn's legendary dissent landed him in exile, while his successors as leaders of the human rights movement, Andrei Sakharov and Alexander Ginzburg, continue to be persecuted by the Soviet government. Dwight MacDonald, Noam Chomsky, and Herbert Marcuse vociferously criticized the United States government for its actions in Southeast Asia, and Howard Zinn urged fellow historians to become leaders of the opposition movement.