Abstract
The words expressing essential concepts and fundamental ideas about legal and political theory and practice do not always recur with the same meaning, but they assume a different meaning depending on the different historical and geographical configurations of the civil and political society. The same thing is for the rule of law and for the relative concept of legality. Here, we want to give a hint of how the concept of legality has changed with reference to the evolution of the form of the State, from the legal State to the social State and, finally, to the constitutional State. The last metamorphosis of legality seems to show the loss, or at least, a deep crisis of fundamental elements, first of all the certainty of law, which had marked the structure and the ideals of the traditional concept of legality.