For a Medieval thinker, in addition to positive law, there is another more fundamental law which is known by analyzing our own rational nature and our ultimate end. In this monographic issue, the nature and reach of the natural law will be studied in various medieval authors (St. Augustine, Alcuin of York, Philip the Chancellor, William of Auxerre, St. Bonaventure, St. Thomas Aquinas, John Duns Scotus and William of Ockham).