"To a greater or lesser extent, we all know that we are paranoid, and our paranoia may take major or minor forms," writes Claude Olievenstein. "But who has not imagined that they are masters of the universe? Or fantasised a thousand tortures for real or imagined enemies? Who has not been driven by jealousy or passion to interpret--or misinterpret--the behaviour of loved ones, overprotecting them and refusing to see their faults? " We all partake of this mystery and must delve into it to understand its various forms, from border-line cases to raving madness, from states of hyperactive intuition to systems of delirium.

"Human beings, whether weak or strong, powerless or empowered, are preyed upon by anxieties that can render them helpless. They can be terrorised by a small mouse or a ridiculous spider. "It depends on very little whether these fears remain under control and produce positive results--or lead to murders, dramatic situations, or dictatorships. It is these minor incidents that I have tried to track down, describe and understand." Claude Olievenstein is the head doctor of the Centre Médical Marmottan in Paris, and director of research at the University of Lyon. He is the author of Non-dit des Emotions (Opus series, No. 18, 1995), published by Editions Odile Jacob.