ERASTUS, THOMAS, ERASTIANISM: Swiss Reformed physician and theologian; b. probably at Baden (14 m. n.w. of Zurich), Switzerland, Sept. 7, 1524; d. at Basel Jan. 1, 1583. The name is Grecised from Lüber or Lieber. He studied theology at Basel and philosophy and medicine for nine years at Bologna and Padua. In 1558 he became physician in ordinary to the elector Palatine, Otto Henry, and professor of medicine at Heidelberg. In 1580 he went to Basel as professor of medicine and became also professor of ethics shortly before his death. He was considered a good physician and upright man, and established a foundation for the education of poor students in medicine at Basel and Heidelberg. As a student of nature he strenuously opposed the astrology, alchemy, and magic of Paracelsus and his school, though he approved of the death penalty for witches. It is as a theologian, however, that he is known and remembered. He was a follower of Zwingli, took an active part in the conferences at Heidelberg (1560) and at Maulbronn (1564), and defended the Swiss view of the Lord's Supper in a book Vom Verstand der Wort Christi: Das ist mein Leib, and again in a vindication of this work against Johann Marbach, a Lutheran minister of Strasburg (Heidelberg, 1565). Some years later he had occasion to defend his master's ideas against the Calvinists in a question of church polity. There was a Calvinist party in Heidelberg, headed by Caspar Olevianus (q.v.), which wanted to introduce a purely Presbyterian constitution, with a corresponding church discipline. Erastus strongly opposed the movement, but in vain. He was himself the first victim of the established discipline, being excommunicated on a charge of latent Unitarianism; after five years, however, he was restored.
Six years after his death G. Castelvetro, who had married his widow, published a work, written in 1568 and found among his papers, Explicatio gravissimæ quæstionis utrum excommunicatio . . . mandato nitatur divino an excogitata sit ab hominibus (Poschiavo, 1589). The book, written after the fashion of the time in the form of theses, denies that excommunication is a divine ordinance, or that the Church has any power to make laws or decrees; and asserts that to inflict pains and penalties and to punish the sins of professing Christians belongs to the civil magistrates, not to pastors and elders. It attracted much attention and was attacked by Beza. English translations appeared at London in 1659 and 1682, and again, by R. Lee, at Edinburgh, 1844. Its views were adopted by a distinct party in the Westminster Assembly, headed by Selden, Lightfoot, Coleman, and Whitelocke. Since that time the doctrine of state supremacy in ecclesiastical causes generally goes under the name of Erastianism; though in its broad sense and wide application this doctrine is by no means due to Erastus or in accord with his views.