This is the frightening prospect, soberly presented by Michael Barkun in his important, just-published book A Culture of Conspiracy: Apocalyptic Visions in Contemporary America. To understand the novelty of this potential requires knowing something about the history of conspiracy theories.

Fears of a petty conspiracy - a political rival or business competitor plotting to do you harm - are as old as the human psyche. But fears of a grand conspiracy - that the Illuminati or Jews plan to take over the world - go back only 900 years and have been operational for just two centuries, since the French Revolution. Conspiracy theories grew in importance from then until World War II, when two arch-conspiracy theorists, Hitler and Stalin, faced off against each other, causing the greatest blood- letting in human history.

THE MAJOR new development, reports Barkun, professor of political science in the Maxwell School at Syracuse University, is not just an erosion in the divisions between these two groups, but their joining forces with occultists, persons bored by rationalism. Occultists are drawn to what Barkun calls the "cultural dumping ground of the heretical, the scandalous, the unfashionable, and the dangerous" - such as spiritualism, Theosophy, alternative medicine, alchemy, and astrology.