geometry non-Euclidean. See NON -EUCLIDEAN GEOMETR. Gerson, Jean de, original name, Jean Charlier (1363–1429), French theologian, philosopher, and ecclesiastic. He studied in Paris, and succeeded the nominalist Pierre d’Ailly as chancellor of the university in 1395. Both d’Ailly and Gerson played a prominent part in the work of the Council of Constance (1414–18). Much of Gerson’s influence on later thinkers arose from his conciliarism, the view that the church is a political society and that a general council, acting on behalf of the church, has the power to depose a pope who fails to promote the church’s welfare, for it seemed that similar arguments could apply to other forms of political society. Gerson’s conciliarism was not constitutionalism in the modern sense, for he appealed to corporate and hierarchical ideas of church government, and did not rest his case on any principle of individual rights. His main writings dealt with mystical theology, which, he thought, brings the believer closer to the beatific vision of God than do other forms of theology. He was influenced by St. Bonaventure and Albertus Magnus, but especially by Pseudo-Dionysius, whom he saw as a disciple of St. Paul and not as a Platonist. He was thus able to adopt an anti-Platonic position in his attacks on the mystic Ruysbroeck and on contemporary followers of Duns Scotus, such as Jean de Ripa. In dismissing Scotist realism, he made use of nominalist positions, particularly those that emphasized divine freedom. He warned theologians against being misled by pride into supposing that natural reason alone could solve metaphysical problems; and he emphasized the importance of a priest’s pastoral duties. Despite his early prominence, he spent the last years of his life in relative obscurity. E.J.A.