Diego de Acebo

Diego de Acebo, also known in the sources as Diego de Acebes or Didacus of Osma, was a Castilian churchman who served as bishop of Osma from 1201 until his death in 1207. Before his elevation he had been prior of the cathedral chapter of Osma, a community of canons regular living under the Rule of Saint Augustine. Surviving medieval records do not preserve his year or place of birth, and almost nothing is known of his family, education, or career before he appears as prior and then bishop. His historical importance rests on that brief episcopate and on his close association with Dominic of Caleruega, a younger canon of the same chapter who accompanied him on his journeys and later founded the Order of Preachers.

In 1203 or 1204 King Alfonso VIII of Castile sent Bishop Diego on a diplomatic embassy, described in the earliest Dominican narrative, the Libellus of Jordan of Saxony, as a journey to the Marches, later commonly identified with Denmark, in order to obtain a bride for the king’s son Ferdinand. Dominic went with him. The mission failed when they found that the intended princess had died. Returning through Languedoc, they spent a night at Toulouse in disputation with a Cathar innkeeper, whom early tradition says they converted. What they observed of the strength of dualist heresy in the region, together with that encounter, shaped Diego’s later sense of missionary vocation.

Diego then went to Rome and asked Pope Innocent III for leave to resign the see of Osma so that he might preach among the pagan Cumans or in some other mission field. The pope refused the resignation and instead attached him to the Cistercian preaching mission already commissioned against the Albigensians in the south of France. There Diego and Dominic adopted a deliberately apostolic manner of life, traveling on foot and in poverty, in conscious contrast to the mounted retinues of the papal legates, whose display had made little impression on a population accustomed to the austere perfects of the Cathar church. Near-contemporary accounts credit this change of method with greater effect in public disputations. In 1206, at Prouille near Fanjeaux, they established a community for women converted from Catharism, a house often described as the first institutional ancestor of the Dominican nuns.

In 1207 Diego was obliged to return to his Castilian diocese and left Dominic in Languedoc to continue the preaching. Shortly after reaching Osma he died, on 30 December 1207. He received no formal beatification or canonization, and the Catholic Church assigns him no universal feast day. His legacy is that of the bishop who formed and protected Dominic, who introduced a poor itinerant style of Catholic preaching in Languedoc on the eve of the Albigensian Crusade, and who helped plant the community at Prouille. After his death Dominic no longer had an episcopal patron on the ground in France, a circumstance that contributed to Dominic’s decision to seek papal approval for a new order of preachers.