Background. The question about nature and essence of psyche and psychical form of reflection till now is opened in spite of effort of many scientists. As a result the problem of scientific definition of psyche and its nature is being one of the most fundamental problems in psychology.

The Objective of the research is to show: a) where the complexity of solving the problem of psyche lies; b) what logic options of solving this problem that are offered in national psychology, particularly in the works of А.N. Leontev and N.I. Chuprikova, can be adduced and why they are insolvent; c) how it is possible to solve the problem of psyche and mental form of reflection using the major concepts of the reflection theory and adequacy concept of behaviour in constantly changing conditions of reality.

Design. The term “psyche” as a theoretical concept is introduced to explain the ability of living organism (opposed to lifeless) to react to external impact by various activity. Critical analysis of natural-scientific definitions of psyche in the works of А. N. Leontiev and N.I. Chuprikova is presented.

Their discrepancy and insufficient scientific background are shown. Main assumptions of the reflection theory are coined, and further definitions of non-mental forms of reflection (e.g. biochemical, physiological, neurophysiological) and also essence of psyche and specific features of psychical forms of reflection are shown. The paper presents a model that reverberates the author’s idea about the dynamics of the evolving psyche and mental processes (e.g. cognitive, emotional, volitionary) due to which mental forms of reflection and of behaviour regulation are fulfilled.

Results. The analysis of natural-scientific definitions of psyche and mental form of reflection that the national psychology dwells upon show their inconsistency and scientific insolvency. The author's version of solving the problem of psyche and determining specific features of mental form of reflection are given an account based on the major concepts of the reflection theory and the need for behaviour adequacy.

Conclusions. In order to shape the essence of psyche, specific features of mental form of reflection and features of mental processes it is necessary to distinguish forms of reflection, allocation of their functions and constraints. Reflection which can be attributed to non-mental (e.g. biochemical, physiological, neurophysiological) form, does not allow to provide behaviour adequacy in a rapidly changing conditions of reality. Based on reflection, behavior always occurs with certain delay in time. If eliminated, this drawback is provided by occurrence of a brain and a property named “psyche”, which provides mental form of reflection as reflection of the near future of objective reality.

In this paper the outcomes of the continuous studies of will are analyzed. The concept of “will” and the concept of “sense” were introduced in the ancient psychology as theoretical constructs. Later these concepts were replaced with narrower ones that now reflect various psychic processes. The whole concept of “will” has changed through time. In the 20th century it was perceived as a separate psychic process of an unknown nature, that is why K. Levin has even proposed excluding this concept from psychology.

The first outcome can be summarized as follows. It is essential to analyze the way concepts are introduced and developed in terms of a particular science. The reason is that all the basic psychological concepts were initially introduced not to reflect the realities, but to explain them as theoretical constructs. Moreover, it is important to consider the possibility of initial constructs differentiation. For instance, mind can branch out into perception, notion, imagination and thinking. In Russian psychology, the concept of will as a capability of overcoming inner and outer barriers was in active use until the 70-ies. The nature of this phenomenon was unknown. Only the analysis of a willful act generation and the way the concept of will was introduced scientists to formulate the task of identifying the mechanisms of a willful act itself.

The second outcome is as follows. To solve a problem it is needed to replace it with a task to complete. For instance, to understand the nature of will we can replace the problem of its understanding with a task of generating a willful act, compensating for the deficiency of initial motivation.

The third outcome is that it is essential to coordinate a new concept with all the rest concepts of that particular science.

The author explores the issue: What does psychology study? Does it study the human psyche? He argues about the product of mental activity. Different views on the subject of scientific psychology, the human psyche and its manifestations are considered.

The main stages of the life and work of M. Lomonosov, the outstanding national scholar, are presented. The features of his personality and outlook are shown. M. Lomonosov’s contribution to the development of scientific psychological thought in Russia is disclosed.