He studied in Paris at the Collège de Navarre,[1] receiving the licentiate in arts in 1367 and the master’s a year later,[2] and was active in university affairs by 1372.

In the spring of 1379, d'Ailly, in anticipation even of the decision of the University of Paris, had carried to the pope of Avignon, Clement VII, the "role" of the French nation.

The dissatisfaction displayed shortly after by the government obliged the university to give up this scheme, and this was probably the cause of Pierre d'Ailly's temporary retirement to Noyon, where he held a canonry.

Both were involved in expelling the Dominican Order from the university for refusing to embrace the idea of the Immaculate Conception and in the effort mentioned above to end the Great Schism by means of an ecumenical council.

When Antipope Benedict XIII succeeded Clement VII at Avignon in 1394, d'Ailly was entrusted by the king with a mission of congratulation to the new pontiff.

His obsequious language on this occasion, and the favours with which it was rewarded, formed a too violent contrast to the determined attitude of the university of Paris, which, tired of the schism, was even then demanding the resignation of the two pontiffs.

[1] The suspicions aroused by his conduct found further confirmation when he caused himself—or allowed himself—to be nominated bishop of Le Puy by Benedict on 2 April 1395.

Two years later, before the same pontiff, he preached in the city of Genoa a sermon which led to the general institution, in the countries of the obedience of Avignon, of the festival of the Holy Trinity.

[1] At the ecclesiastical council which took place at Paris in 1406, d'Ailly made every effort to avert a new withdrawal from the obedience and, by order of the king, took the part of defender of Benedict XIII, a course which yet again exposed him to attacks from the university party.

The following year he and his disciple Gerson formed part of the great embassy sent by the princes to the two pontiffs, and while in Italy he was occupied in praiseworthy but vain efforts to induce the pope of Rome to remove himself to a town on the Italian coast, in the neighbourhood of his rival, where it was hoped that the double abdication would take place.

At this time he was still faithful to Benedict, and the disinclination he felt to joining the members of the French clergy who were on the point of ratifying the royal declaration of neutrality excited the anger of Charles VI's government, and a mandate, which was however not executed, ordered the arrest of the bishop.

[1] It was not until after the cardinals of the two colleges had led to the convocation of the Council of Pisa (1409) that d'Ailly renounced his support of Benedict XIII, and, for want of a better policy, again allied himself with the cause which he had championed in his youth.

When in France's civil discord the Burgundian faction seized Paris in 1419, killing some professors in the process, he fled south and retired to Avignon.

[15] In The Eighteenth Brumaire of Louis Napoleon, Karl Marx falsely claimed that d'Ailly had told advocates of ethical reform at the Council of Constance, "Only the devil in person can still save the Catholic Church, and you ask for angels.