“ In 1877 he received the degree of docteur ès lettres with two remarkable theses, a dissertation De Macario magnete, and an Étude sur le Liber pontificalis, in which he explained with unerring critical acumen the origin of that celebrated chronicle, determined the different editions and their interrelation, and stated precisely the value of his evidence. Immediately afterwards he was appointed professor at the Catholic Institute in Paris, and for eight years presented the example and model, then rare in France, of a priest teaching church history according to the rules of scientific criticism. ”

“ When a proposal was set on foot to bring about a reconciliation between the Roman Church and the Christian Churches of the East, the Abbé Duchesne endeavoured to show that the union of those churches was possible under the Roman supremacy, because unity did not necessarily entail uniformity. His Autonomies ecclésiastiques; églises séparées (1897) , in which he speaks of the origin of the Anglican Church, but treats especially of the origin of the Greek Churches of the East, was received with scant favour in certain narrow circles of the pontifical court. ”

“ His course, bold even to the point of rashness in the eyes of the traditionalist exegetists, was at length suspended. In November 1885 he was appointed lecturer at the École Pratique des Hautes Études. ”