Journal of Physical Sciences Successes, 1957, August, t. 62, vol. 4. C. 461-474. As has happened many times in the history of physics, the mathematical part of the theory, together with some formal recipes linking theory with experience, was built before the corresponding physical concepts were developed......... The apparatus of non-relativistic quantum mechanics, which does not contain any internal contradictions, was successfully applied to solving specific problems of atomic physics, but its physical interpretation remained unclear for a long time. The need for a proper physical interpretation of the finished apparatus of quantum mechanics has become more and more acute. 1. Attempts at a classical interpretation of the wave function and the reasons for their insolvency. 2. Niels Bohr's ideas and his terminology. 3. Denial of new ideas as a reaction to their positivist interpretation. 4. Relativity to the means of observation . 5. Concept of the device. 6. Essence of dualism wave - particle. 7. Probabilistic description of the interaction between the object and the device. 8. Probabilistic characteristics of the state of the object. 9. The concept of the potentially possible and realized in classical physics . 10. Probability and Statistics in Quantum Mechanics . 11. Forms of Expression of the Principle of Causality in Quantum Mechanics . 12. Philosophical questions posed by quantum mechanics.