In Bonn he had learnt the scientific methods of exact research, but besides being an accurate philologist he was a literary critic of great acumen and breadth of view, and brought a singularly clear mind to bear on his favourite study of medieval French literature.

His Vie de saint Alexis (1872) broke new ground and provided a model for future editors of medieval texts.

He contributed largely to the Histoire littéraire de la France, and with Paul Meyer published Romania, an academic journal devoted to the study of Romance literature.

At the University of Oslo Gaston Paris also held a lecture about the two folktale collectors, Asbjørnsen and Moe, which he believed to be, besides the Brothers Grimm, the best re-tellers of the genre.

Among them were Leopold Pannier; Marius Sepet, the author of Le Drame chrétien au Moyen Âge (1878) and Origines catholiques du théâtre moderne (1901); Charles Joret; Alfred Morel-Fatio; Gaston Raynaud, who was responsible for various volumes of the excellent editions published by the Société des anciens textes français; Arsène Darmesteter; and others.