The article considers the theoretical, practical and natural-scientific fundamentals of the physical education system as provided by P.F. Lesgaft. It shows that the inventor was driven by the ideas of psychophysical integrity of a human and close interconnection of human ethical, intellectual and physical development processes and, hence, the relevant education process aspects. It was based on these ideas that P.F. Lesgaft designed the fundamental provisions of his physical education system that is basically intended to help the child control its own movements in the physical education process by analyzing, matching and assessing the sensations evoked by the muscular activity. Furthermore, the article emphasizes the fact that the notion of "physical education", as interpreted by P.F. Lesgaft, cannot be reduced (as often made by some researchers) to the motor qualities and the relevant knowledge acquisition process as he considered it much wider as a body and personality formation processes going simultaneously.