Flemish Humanist and theologian, b. 15 August, 1513 at Pitthem in West Flanders; d. 3 February, 1566, at Cologne. He studied at Louvain, where he was graduated in 1533. In 1541 he was appointed professor of belles-lettres at Bruges, but resigned two years later, partly from a natural desire to travel for instruction, and partly in consequence of the opposition aroused by his pro-Reformation views. On his journeys, which were undertaken in the company, and at the expense of his friend, Cornelius Wouters, he visited Rome, and in 1544 came to Cologne, where he settled permanently in the summer of 1549. He soon abandoned the classics for the study of the Bible and ecclesiastical questions, and had already published several classical, Biblical, and patristic treatises, when in 1556 he commenced a series of liturgical works. His "Hymni Ecclesiastici" (1556) were followed in 1558 by the "Liturgica de ritu et ordine Dominicæ coenæ celebrandæ". Both publications were placed on the Index. As a completion of the "Liturgica", his "Ordo Romanus" appeared (1558); and in 1560 the "Preces Ecclesiasticæ" were published. Cassander's activity in promoting religious peace between Catholics and Protestants began with the publication of his anonymous book: "De officio pii viri in hoc religionis dissidio" (1561). This work, written at the request of the jurist, Francis Baldwin, and submitted by him to the Colloquy of Poissy (Sept., 1561), gave offence to both sides. Calvin wrote a violent answer, in which he unjustly berated Francis Baldwin as the author of the publication. On the Catholic side, William Lindanus, afterwards Bishop of Roermonde, remonstrated with Cassander by letter, and would have attacked him publicly had it not been for the intervention of a secretary of the King of Spain.
At the request of William, Duke of Cleves, Cassander wrote in 1563 a treatise against the Anabaptists: "De Baptismo Infantium". It was supplemented in 1565 by "De Baptismo Infantium: Pars Altera". The treatise, "De sacrâ communione Christiani populi in utrâque panis et vini specie" (Cologne, 1564), a plea in favour of the reception of communion under both species by the laity, attracted the attention of the Emperor Ferdinand I, who was himself a partisan of the idea. The latter, wishing to use the author as the peacemaker between Catholics and Protestants, invited him to Vienna. Cassander, prevented by illness from acting upon the invitation, wrote his "Consultatio de articulis Religionis inter Catholicos et Protestants controversis", which he addressed to Maximilian II (1564), as Ferdinand I had died before its completion. This work, however, failed to satisfy either side. It is most probable, though not universally admitted, that Cassander died in full submission to the Catholic Church. He certainly always wished to remain a faithful member of the Church; but it is equally certain that some of his opinions were Protestant to the core. He advocated, for example, the division of ecclesiastical doctrines into fundamental and non-fundamental articles, the supremacy of private judgement, and the human origin of the papal primacy. An incomplete collection of his works was issued at Paris in 1616, and placed on the Index the following year.
DE SCHREVEL, Hist. Du semin. De Bruges (Bruges, 1883-95), I, 263-65, 387-609; FRITZEN, De Cassandri ejusque sociorum studiis irenicis (Muenster, 1865); PASTOR in Kirchenlex., s.v.