Against those formalistic lectures of Kant’s practical philosophy, it is assumed a lecture of his ethical proposal from the concept of maxim. When referred to Kant’s moral as a moral of maxims, it is proposed a specific model of the rational action, which enables the application of moral law. The maxim, within this action model, works as subjective practical principle of action from which it is applied the categorical imperative, as an objective practical principle. This implies that Kant’s proposal does not exclude the practical context in which the action is desired, as well as neither the specific situation of the agent of action.