The paper analyzes and discusses 1900-2020. Una storia del diritto naturale, the last book of Francesco Viola, and stresses how this book represents a very important event for the contemporary literature of philosophy of law. In fact, it is hard to hold together different orientations of thought. The work of Viola has the merit of having promptly grasped the relevance of contemporary theories, especially the American ones, of Natural Law, that start not from human nature but from practical reason