Erastus, Thomas, 1524–83, Swiss Protestant theologian, a physician, whose original name was Lüber, Lieber, or Liebler. As a follower of Huldreich Zwingli, he supported the Swiss leader's view of the Lord's Supper at the conferences of Heidelberg (1560) and Maulbronn (1564) and in a book (1565). In spite of his vigorous opposition to the Calvinist doctrine, Presbyterian church discipline and government were introduced in Heidelberg in 1570. In 1574, Erastus was excommunicated by the Heidelberg consistory, but a year later the edict was removed. Much controversy has arisen over his treatise, Explicatio, written in 1568 and posthumously published in 1589. It declares that excommunication is not a divine ordinance and that punishment of sins should be left to civil authorities. Erastus was motivated by his fear of the usurpation of temporal powers by the church. The term Erastianism has come to represent approval of the dominance of civil authority in all punitive measures and, by extension, complete dominance of the state over the church, though Erastus himself never held such an extreme view. Erastianism achieved its definitive expression in the Leviathan of Thomas Hobbes.
See E. Evans, Erastianism (1931).