Empiro-criticism (which means "criticism of experience") sees its task in purifying experience, identifying the content of "pure experience," free from extraneous inputs. From this point of view, the author considers the development of the definition of the subject of psychology - from the naive-empirical phase, which defined psychology as the "doctrine of the soul," to the so-called empiriocritical phase. In this phase on the path of cleansing experience, Avenarius sees an obstacle in the form of introjection, by which he understands the process of attributing to other people the perception of the surrounding things and "putting" these feelings and thinking into other people. Rejecting the theory of introjection, the author puts forward the concept of fundamental coordination, using which he gives answers to questions about the subject of psychology.