After his return, he held various educational positions and earned his doctorate degree with two theses: Quid Vestae cultus in institutis veterum privatis publicisque valuerit[1] and Polybe, ou la Grèce conquise par les Romains[2] (1858).

[3] Fustel de Coulanges was appointed to a lectureship at the École Normale Supérieure in February 1870, to a professorship at the Paris faculty of letters in 1875, and to the chair of medieval history created for him at the Sorbonne in 1878, he applied himself to the study of the political institutions of ancient France.

The dissertations not embodied in his work were collected by himself and (after his death) by his pupil, Camille Jullian, and published as volumes of miscellanies: Recherches sur quelques problèmes d'Histoire (1885), dealing with the Roman colonate, the land system in Normandy; the Germanic mark, and the judiciary organization in the kingdom of the Franks; Nouvelles recherches sur quelques problèmes d'histoire (1891); and Questions historiques (1893), which contains his paper on Chios and his thesis on Polybius.

Without intervening personally in French politics, he took a keen interest in the questions of administration and social reorganization arising from the fall of the imperialist régime and the disasters of the war.

[3] He wished the institutions of the present to approximate more closely to those of the past and devised for the new French constitution a body of reforms which reflected the opinions he had formed upon the democracy at Rome and in ancient France.