On the fictional and real lost gravitation force

The paper covers a critical approach to the natural reality study which is the method of scientific cognition. The existent so called d`Alembert's rule is the link of reality on which the specific attention is focused. The critics is directed to the fictional inertia force covered in the mentioned rule. The necessity for its elimination from the reality description has been presented. Instead, it is proved that a real inertia force occurs. A proper exemplification material has been delivered with two examples of force equilibrium of the system. One of them refers to a rigid system being both under stable and unstable states. The second one covers also these two states but it is referred to a mass-flexible system. Finally, the discussed solution of the problem has been explained on the example of mathematic pendulum and a mass-string system.