one of the four great mendicant orders of the Roman Catholic church, was founded by St. Dominic (Dominic, Saint) in 1215. Dominic, a priest of the Spanish diocese of Osma, accompanied his bishop on a preaching mission among the Albigensian (Albigenses) heretics of southern France, where he founded a convent at Prouille in 1206, partly for his converts, which was served by a community of preachers. From this developed the conception of an institute of preachers to convert the Albigensians, which received provisional approval from Pope Innocent III in 1215. Dominic gave his followers a rule of life based on that of St. Augustine (Augustine, Saint) and made his first settlement at Toulouse; on Dec. 22, 1216, Pope Honorius III gave formal sanction. The novelty of the institute was the commission to preach Christian doctrine, a task previously regarded as the prerogative and monopoly of bishops and their delegates; a corollary was the obligation of theological study, and, as early as 1218, Dominic sent seven of his followers to the University of Paris.

From the beginning the order has been a synthesis of the contemplative life and the active ministry. The members live a community life; and a careful balance is maintained between democratically constituted chapters, or legislative assemblies, and strong but elected superiors. In contrast to the monastic orders that predated it, the Dominican order was not a collection of autonomous houses; it was an army of priests, organized in provinces under a master general and ready to go wherever they were needed. The individual belonged to the order, not to any one house, and could be sent anywhere at any time about its business; this innovation has served as a model for many subsequent bodies.

Within 40 years of the order's foundation, talented members were concentrated in the schools at Paris, Bologna, Cologne, and Oxford; many eminent masters of the universities (university) took the Dominican habit and became in time regents in the friaries. Originally students of theology only, and with no distinguishing philosophical opinions, they were led by Albertus Magnus (Albertus Magnus, Saint) and his pupil Thomas Aquinas (Aquinas, Thomas, Saint) to a study of the newly available works of Aristotle (Aristotelianism) that had been transmitted to Europe by Muslim scholars and to the integration of philosophy and theology. After a short initial opposition, the system of St. Thomas Aquinas (Thomism) was adopted as official (1278). Meanwhile, the Dominicans pursued their vocation to preaching. In southern France they spoke out against the Albigensians and, in Spain and elsewhere, against the Moors and Jews. They evangelized the non-Christians in northern and eastern Europe, in the lands of the eastern Mediterranean, and in India. When the inquisition was established, Dominicans were entrusted with its execution. They were among the first and most energetic missionaries (mission) in the “expansion of Europe” under the Spanish and Portuguese explorers and later under the French. In modern times they have broadened their preaching apostolate to include work in the fields of radio, television, films, and stage.

The Dominican order has continued to be noted for an unswerving orthodoxy, based upon the philosophical and theological teaching of Aquinas, and has steadfastly opposed novelty or accommodation in theology. The 19th and 20th centuries have witnessed a tremendous development of congregations of Dominican sisters engaged in teaching, nursing, and a wide variety of charitable works. Some of these congregations, such as the Maryknoll Sisters, are devoted to work in foreign missions.