It is commonly accepted that the theory of activity by A.N. Leontiev was the attempt to overcome so called “word-centrism” developed by L.S. Vygotsky. At the same time there are some arguments, that theory of activity was developed to solve the problem, which had been formulated by Vygotsky. He tried to overcome double-factorial determination of psychic, i.e. to go from social to psychological determination. To solve the problem Vygotsky modified his own theory and changed the main concept from high mental function to system structure of conciseness and interfunctional interactions. Vygotsky suggested emotional experience as the unit of psychic. Group of psychologists worked in Kharkov tried to solve this problem in another way. They supposed that activity mediates as social, as physiological factors. This decision was more materialistic from their point of view. Reveling the real basic theoretical problem of theory of activity is important for understanding its main statements and experimental results. Analysis of investigations, conducted by the adepts of the theory of activity, leads to understanding of holistic nature of activity.