Isidore of Seville, St

Isidore of Seville, St (c. 560-636), Spanish theologian, archbishop, and encyclopedist, whose most influential work was Etymologiae, a remarkably comprehensive early encyclopedia. He was born in Seville and was educated at a monastery under the supervision of his brother St Leander, whom he later succeeded as archbishop of Seville. As archbishop, Isidore helped unify the Spanish Church by converting the Visigoths, who had completed the conquest of Spain in the 5th century, to orthodox Christianity from Arianism—one of the most divisive heresies in the history of the Church. He also presided over a number of important Church councils. Most notable among these was the fourth national Council of Toledo (633), which decreed the union of Church and state, the establishment of cathedral schools in every diocese, and the standardizaton of liturgical practice.

Chief among Isidore's writings is the Etymologiae, in which he attempted to compile all secular and religious knowledge. Divided into 20 sections, it contains information that Isidore drew from the works of other writers and Latin authorities. The Etymologiae was a favourite textbook for students during the Middle Ages, and it remained for centuries a standard reference book. Isidore's other works include treatises on theology, Scripture, linguistics, science, and history. His Sententiarum Libri Tres (Three Books of Sentences) was the first manual of Christian doctrine and ethics in the Latin Church.

Isidore died in Seville on April 4, 636. He was canonized in 1598 and declared a Doctor of the Church in 1722. His feast day is April 4.