[3] During the 1920s he taught at Harvard and his Philosophy and Civilization in the Middle Ages was published at Princeton in 1922.

De Wulf contributed articles relative to philosophy to the Catholic Encyclopedia.

[3] Very early it was noted that "In his Histoire de la Philosophie Médievale, Mr. de Wulf departs from the common view which identifies Scholasticism with Mediaeval philosophy, and discovers in the Middle Ages two antithetical currents: Scholasticism proper, represented by Thomas Aquinas, Duns Scotus, Albert the Great, etc.

; and anti-Scholasticism, of which Scotus Erigena is the father, and which is continued by the Catharists, the Albigenses and the Pantheistic schools.

Mr. de Wulf, however, still holds the same opinion, and has defended it again in his Introduction à la Philosophie Neo scolastique.