As its main goal, the paper defends the rationality of the concept of equilibrium in secure strategies (EinSS) and the organic proximity of the logic of this concept to the logic underlying the classical approach to solving game problems through Nash equilibrium. The article deals in detail with the system of EinSS definitions through the prism of the Nash equilibrium concept. On the basis of this analogy the connection between the existence of EinSS and the existence of Nash equilibrium is established.