The essay portrays the different layers of the new religious idea by Martin Luther. Within the accurate and contextualized historical picture, the author points out how the profound meaning of the bold revolution by the German monk was dictated not only by the will of contrasting the growing temporal power of the Pope, but in particular way by the “faith alone” principle. The author explains that, despite the succeeding forgetfulness of this idea by liberal protestants, it became one of the most persuasive and powerful arguments among the reformation theologians of XX century.

The essay also gives a brief overview of the development of the idea of sola fide both in the newborn Lutheran thought and in the contemporary Italian catholic writings, especially those coming from the pages of the authors like Gaspare Contarini. The comparison allows observing different approaches to the concept that will split the Western Church into two diversified traditions.