The Life and Scientific Efficiency of Volf Solomonovich Merlin

In 2023, the 125th anniversary of the birth of Volf Solomonovich Merlin was celebrated. He is a well-known Russian psychologist, author of the theory of integral individuality, and founder of the Perm Scientific School of Psychology. The purpose of this article is to present the main milestones of Merlin's life and scientific work. The biography of the scientist is briefly under consideration, and the periodization of his scientific path takes into account. Four periods highlight his scientific efficiency, namely, 1924–1939 (pedology); 1940–1955 (differential psychology); 1956–1971 (personality psychology); 1972–1982 (system and integral approach to the study of human individuality). Further, the theory of integral individuality reveals its main features. The aim of the theory is to show a holistic fashion of a human's individuality. The integral means the study of individuality according to the criteria of hierarchy, teleological and causal determination, and polymorphism. The estimation of Merlin's scientific heritage points out its perspective nowadays. The Russian scientific community appreciates the contribution of Merlin’s scientific achievement due to which Russian psychology develops.