In this study, Kripke's claim, that within the framework of the possible worlds argument, the identification of mental processes by being reduced to physical events doesn't have an imperative base is addressed. Theories of physicalism and identity aims to explain the mental processes in a thoroughly physical way, thus trying to reduce it to the physical one, through brain events. According to Kripke, there must be an imperativeness for the identification of mental states with physical states. According to him, however, (...) it is not possible to show that physical events necessarily reveal mental processes. According to Kripke, in order to be imperatively correct for one statement, it must be correct in all possible worlds. Kripke uses the concept of "rigid designator" to describe this situation. According to Kripke, the thesis of identity between rigid designators must be metaphysically imperative correct. This situation does not apply to mental events. So then, the aim of this article is to reveal why the thesis of identity proposed in the explanation of physical and mental situations in terms of Kripke is not valid. (shrink)