fanatism

Sometimes you can recognize a fanatic just by the peculiar glitter in his eyes, or by the distortion of his face by the repetitiveness and sterility of his argument, and very importantly, by his lack of interest in others and in the problems of others, except those in which his own narcissism is invested. (…) It is not too difficult to distinguish between the personality of one who is a seeker of reality and truth, and one who is a self-seeker and narcissist, convinced that something is true for the only reason that it is what he believes in. Needless to add that fanatics are often very effective; precisely because they are so far away from reality they have no doubts whatever, and they talk with a kind of absolute conviction which is appealing to the many who doubt and look for God in the man they can hear and touch. ― (1990i [1968]: Political Radicalism in the United States and Its Critique. So far not published in English.)