Numa Fustel de Coulanges (1830-1889), archeologist, had taught at Strasbourg university from 1860 to 1870 and from 1870 taught in Paris (first at the Ecole Normale Supérieure, then at the Sorbonne). His work in the 1870s argued that the Frankish/Germanic settlement of Gaul was a matter of absorption (leaving a Gallo-Roman institutional continuity intact) rather than a conquest. The present text, written in rebuttal of Theodor Mommsen’s open letters to the Italians, first appeared in the Revue des Deux Mondes. His argumentation foreshadows that of Renan’s Qu'est-ce qu’une nation? as well as the 1914-1918 wartime propaganda of his pupil Camille Jullian.