Alfonso Maria de' Liguori," the holiest Neapolitan saint and the best Neapolitan of all the saints", with his theological reflection and his pastoral activity has given a new perspective to the Christian life. He was an outstanding figure of the XVIII Century Neapolitan cultural society. His reflection on the theme of the conscience underlines the authenticity of the religious experience and awards de' Liguori a first rank in the contemporary society.