Pierre d'Ailly

Pierre d'Ailly (1351–1420) was a prominent French theologian, astrologer, and cardinal of the Roman Catholic Church. Born in Compiègne, he studied at the Collège de Navarre in Paris, where he became deeply involved in university affairs. D'Ailly held various academic and ecclesiastical positions, including rector and chancellor of the University of Paris, Bishop of Le Puy, Bishop of Noyon, and Bishop of Cambrai. He was elevated to the rank of cardinal in 1411. D'Ailly was a key figure during the Western Schism, actively participating in efforts to resolve the division within the Church. He was involved in the Council of Pisa (1409) and played a crucial role in the Council of Constance (1414–1418), advocating for church reform and union. His writings covered theology, astrology, and cosmography. His work "Imago Mundi" influenced Christopher Columbus's understanding of the Earth's size. D'Ailly's later life saw him retire to Avignon, where he died in 1420.