Conspiracy: How the Paranoid Style Flourishes and Where It Comes from.

Conspiracy: How the Paranoid Style Flourishes and Where It Comes From, by Daniel Pipes (Free Press, 258 pp., $25)

Mr. Stuttaford knows what you are planning.

POOR, sad Princess Diana. Within hours of the tragedy in Paris, her death was being honored in the way most characteristic of our time: a conspiracy theory relayed over the Internet. She was murdered, you see, by British intelligence. The mother of a future King of England could not be allowed to marry an Egyptian. Ridiculous, of course, although Muammar Qaddafi seemed to think that there was something to it.

Which would not surprise Daniel Pipes. His fascinating, though all too brief, new book traces the development of conspiracy theories from the time of the Crusades to the Roswell era. Naturally the Libyan leader makes an appearance. But, to be fair, he is no more deranged than many in the dismal crowd that Mr. Pipes summons for our inspection. For, as he explains cheerily, "this book is the opposite of a study in intellectual history. [It deals] not with the cultural elite but its rearguard, not with the finest mental creation but its dregs . . . So debased is the discourse ahead that even the Russian secret police and Hitler play important intellectual roles." Well, that's encouraging.

With depressing effectiveness, the author shows how we have allowed ourselves to be seduced again and again by variants of the same couple of stories. And if there is a conspiracy there must be conspirators. Freemasons, perhaps, or maybe the Trilateral Commission. And don't forget the Jews.

The conspiracy theorists never have, something that Daniel Pipes dates back to the Crusades. Jews became a convenient local proxy for the Muslim enemy. In a cruel paradox, as the pogroms intensified so did the idea that the Jews were planning a terrible vengeance. That fear in turn provoked further repression, and the cycle that was never really to end had begun. It is a plausible view, but, as the author concedes, it has a problem. Why pick on the Jews when "Muslims constituted a so much more substantial presence and threat"? Mr. Pipes never says, preferring merely to point to a pattern whereby "alleged conspirators are rarely those whom logic might point to."

For this is not a book that dwells on the psychological causes of conspiracism. This is a pity. It is a central question, and the answer is probably not too difficult to find. Take an obsessive personality, pour in a trauma or two, and garnish with a little paranoia. Add war, revolution, economic depression, or plague. When we are confronted with such vast, often incomprehensible cataclysms, a conspiracy theory can be a comfort. It provides an answer to people's questions and an object for their anger. It can also be fun. Winston Smith enjoyed his Hates.

Mr. Pipes touches on this, but he spends far more time describing the symptoms of the disease. He does this well. And it is a disease. At least from the point where an interest in conspiracy theories tips over into "a way of seeing life itself. This is conspiracism. . . . It begins with belief in an occasional conspiracy theory . . . and ends with a view of history that dwells largely or exclusively on plots to gain world power or even destroy the human race."

Compulsively autodidactic, conspiracists live in a dark universe illuminated only by a vast and self-referential literature (two thousand books on the Kennedy assassination alone since 1963). Bolstered by obscure factoids and outright forgeries, its authors peddle theories of astonishing complexity. The right answer is never obvious and the obvious is never right. Readers are pushed further and further into irrationality. Which is not surprising. As the core belief of conspiracism is that all appearances are intended to deceive, reality itself becomes an illusion, a dangerous trick rather than a wake-up call.

In the West, at least, Pipes feels that conspiracism is in retreat, discredited by the twin failures of Communist Russia and Nazi Germany. "Hitler and Stalin had established the hideous price of conspiracy theories running rampant."

Let's hope so. But there is something a little Fukuyama-annish about such a view. We live, after all, in an age of rapid and highly unpredictable change. Even in this relatively benign era conspiracy theories continue to flourish. Most are not serious, just couch-potato mythologizing; but they can act, Mr. Pipes concedes, as a pathway to more dangerous fantasies -- Timothy McVeigh is, apparently, a believer in UFOs. Above all, they serve to chip away at the shared assumptions of truth that must underpin society.

In the case of American blacks this may already have happened. Mr. Pipes lists some of the conspiracy theories that circulate in this community, but without appearing unduly concerned. He may be too relaxed. From the idea that AIDS was developed as a genocidal tool (as a supplement, doubtless, to the crack distributed in the ghetto by the CIA) to kente-clad anti-Semitism, there is plenty to suggest that a dangerous conspiracism has already taken root in an important part of American society. Its success may suggest that conspiracism remains more of a threat than Mr. Pipes would have us believe.

Perhaps he is trying to trick us.