An heterodox book, which instead of offering a traditional approach to the theory of Law, it focuses on its criticisms and uncertainties, so it flourish original thoughts that add value. In the first part, it analyzes the nature of justice over time and unravels the tight skein of theories and approaches that exists until they are reduced to a few simple characteristics with which to operate: history, logic and philosophy. The second part, studies the sources of Law to obtain an image as accurate as possible about the origin and function of Law and Justice.