Group psychosis is one of the most important causes of war. Group psychosis differs from individual psychosis in regard to the capacity of its victims for making contacts. While the loss of contact of a person with his or her surroundings is the decisive criterion of individual psychosis, contacts between members of a group under the influence of group psychosis are unimpaired. The phenomenon known as 'folie à deux' (communicated insanity) is fundamental in establishing a group psychosis and it is the paranoiac, owing to his strong narcissism, who is particularly apt to induce other people to believe in his paranoiac system. 'The man who does not love anything or anybody but himself easily becomes the love object of others, and the man who does not admit any criticism of his own actions readily criticises the actions of others'. By the identification of