The French scholar and cardinal Pierre d'Ailly (1350-1420) is known chiefly for his efforts in healing the Western Schism of the Church. His scientific and philosophical writings are also important.

Pierre d'Ailly was born at Compi'ne. He spent most of his life in association with the University of Paris, graduating in theology from the College of Navarre in 1380 and becoming master of the college in 1384 and chancellor of the university in 1389.

One of the university's chief concerns was the Western Schism (1378-1417), in which rival popes claimed legitimacy. At first D'Ailly supported the Avignon pope Benedict XIII, but he soon became a radical leader of the Conciliar movement. The Conciliarists argued that a general council of the Church is superior to the pope and that therefore a general council could end the schism by choosing a new pope satisfactory to all parties. D'Ailly played a prominent part at the Council of Pisa (1409), which elected a new pope, Alexander V. In 1411 Alexander's successor, John XXIII, made D'Ailly a cardinal. When the rival popes refused to resign, however, the Council of Constance (1414-1418) was called. D'Ailly was an acknowledged leader and effected the decision to have the contending popes abdicate. The council then elected a new pope, Martin V, and the schism was ended. D'Ailly himself was a candidate for the papal throne, but he lost the election because of opposition from France's enemies, England and Burgundy. He retired for safety to Avignon, where he served Martin V.

Pierre d'Ailly wrote prolifically. His works on the nature of the Church had the most lasting influence. He developed the theory of conciliarism and the concept that the only infallible body in the Church is the whole of the faithful. These ideas were later shared by the Protestant reformers. He was an advocate of the calendar reform later made by Pope Gregory XII; and, like many important thinkers of his day, he took great interest in astrology, which he felt was consistent with religion. His book on geography, Imago mundi, was read carefully by Columbus, who said that it inspired his voyage of 1492 by suggesting the feasibility of sailing from Spain west to India. D'Ailly also wrote on astronomy, meteorology, mathematics, logic, metaphysics, and psychology. He died in Avignon in 1420.

Further Reading

A biography of Pierre d'Ailly in English is John P. MacGowen, Pierre d'Ailly and the Council of Constance (1936). There are two good studies for D'Ailly's conciliar theories: E.F. Jacob, Essays in the Conciliar Epoch (1943; rev. ed. 1963), and Brian Tierney, Foundations of the Conciliar Theory: The Contribution of the Medieval Canonists from Gratian to the Great Schism (1955). For D'Ailly's actions at Constance and some documents of the event see Louise Ropes Loomis, The Council of Constance: The Unification of the Church (1961).

Additional Sources

Guenaee, Bernard, Between church and state: the lives of four French prelates in the late Middle Ages, Chicago: University of Chicago Press, 1991.

For more information on Pierre d'Ailly, visit Britannica.com.

(pyĕr dāyē') , 1350–1420, French theologian and writer, cardinal of the Roman Catholic Church. He was the teacher of John Gerson and was Gerson's predecessor as chancellor of the Univ. of Paris (1385–95). Ailly figured prominently among the conciliarists working to end the Great Schism (see Schism, Great). He urged that an ecumenical council be called to name a new pope as the only means of settling the schism. He seems to have been more concerned with a practical solution than with the implications of the conciliar theory. He participated in both the Council of Pisa (see Pisa, Council of) and the Council of Constance (see Constance, Council of). At Constance Ailly took part in the trial and condemnation of John Hus. His vast writings embrace theology, philosophy, cosmography, plans for ecclesiastical reform, and French religious verse. One of his works, the Imago mundi, an astronomical compendium, was studied by Columbus.

Bibliography

See studies by J. P. McGowan (1936) and F. Oakley (1964).

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