The principle of reflection was а cornerstone of the Soviet psychology. The largest Russian psychologists of the Soviet period, including the leader of the St. Petersburg Psychological School Boris Ananiev, contributed to his justification and development. In Ananiev‘s theory, the principle of reflection took the form of materialistic sensationalism. A disciple of B. Ananiev, L. Vekker proceeded from the understanding of mental processes as a particular form of information processes. Dozens of research of sensory-perceptual and other processes were theoretically summarized in some monographs of St. Petersburg school. The necessity of an adequate image of the world as means of adaptation and survival, activity and creativity make the principle of reflection undeniable. The principle of reflection is now criticized by supporters of constructionism.