Mental actions formation: Mysteries puzzled out and not.

The method of intelligent processes formation by P.Ya. Galperin takes as principal a depiction of structure of activity hidden from sense but existing as objective reality. A problem of logic bases and sources as well as of the structure of mental actions is point at issue of the article. Compared are the of the philosophers’ views (Plato, Aristotle, Meister Eckhart, Hegel) and of psychologist’s (J. Piaget, L. Vygotsky, A.N. Leontiev) on the grounds of mental structures determination. Unsolved problems of mental actions determination are emphasized.