The article demonstrates the inadequacy in the traditional approach of psychology to the description of products of mental representation of perception. The principles of objective representation of subjective experience (principles of “mental map” construction) contain a whole range of contradictions. We propose a consistent mathematical description of the “mental map” based on psychosemiotic principles. Instead of the classical space of characteristics/properties we introduce semantic space that opens the way to a truly adequate representation of psychic reality. The article discusses metrics of the mental map, as well as substantiates the possibility of applying conservation laws to psychology. It is shown that it is possible to reach an adequate representation of research object in the humanities, equivalent to that of natural sciences in terms of accuracy. To verify a new approach, we make use of our theoretical deductions in the explanation of experimental data widely known in psychophysics and inconsistent with Stevens law.