SUMMARY: On the basis of the thought of St. Augustine, during the scholastic period the three Franciscan masters Alexander of Hales, Bonaventure and John Duns Scotus developed and deep­ened in the same direction a doctrine of natural law. While Alexander of Hales and Bonaventure, following St. Augustine, limited their reflections to the theological aspects, John Duns Scotus rooted his doctrine of natural law in philosophical speculation, thus initiating a new systematic which became widespread and has remained unchanged until today.