INTRODUCTION. The present work aims to analyze and comment on a document that has been marked since its publication in 1947, a model of critique of political systems through the historical analysis. An essay entitled the Mexico Crisis of Cosio Villegas has not lost its critical and historical value. Since then, you can resort to him to understand the particular political climate of the Decade of the forties and fifties in our country. But its value is more extensive. Is focus: in a few pages, Cosio Villegas manages to make an accurate diagnosis of the weaknesses and vices of the project of nation that emerged from the Mexican Revolution; and is it of political ethics: as a liberal who was Cosio Villegas here offers a defense of freedom not as ultimate goal of social development, but as procedure to achieve it. The text was published in 1947 in the popular magazine notebooks Americans of the University Nacional Autonoma of Mexico, founded by Jesus Silva Herzog in 1942 However, Villegas test won fame nationally for its publication in the newspaper Excelsior, which favored that you reached a broader audience (Cansino, 2005: 40). The trial of Daniel Cosio Villegas is not intended to be a scholarly text destined for the Chair; its objective is different: make a direct and scathing criticism of the elite ruling in the country that had a massive diffusion. This is why he does not use a technical and complex language, but its pages to denote a more personal work, based on his experiences at the end of the Porfiriato, of the revolutionary period and the subsequent emergence of the hegemonic group, to which accuses of being an exact copy of the previous bourgeois elites. During the years prior to the publication of the essay of Villegas, Mexico began to live a new stage of realignment of its political class.