The known work of classic of psychology Leon Фестингера is in modern exposition. A concept "Когнитивный dissonance" densely entered our life ‒ this psychological phenomenon affects our behavior and world perception. People aspire to the internal equilibrium between the got information and personal reasons of the behavior - sometimes even despite good sense. Aspiration to bring down a dissonance is major by a requirement in life of any man ‒ an author proves it the results of numerous experiments and surprizing historical facts.