JONAS, JUSTUS (1493–1555), German Protestant reformer, was born at Nordhausen in Thuringia, on the 5th of June 1493. His real name was Jodokus (Jobst) Koch, which he changed according to the common custom of German scholars in the 16th century, when at the university of Erfurt. He entered that university in 1506, studied law and the humanities, and became Master of Arts in 1510. In 1511 he went to Wittenberg, where he took his bachelor’s degree in law. He returned to Erfurt in 1514 or 1515, was ordained priest, and in 1518 was promoted doctor in both faculties and appointed to a well-endowed canonry in the church of St Severus, to which a professorship of law was attached. His great admiration for Erasmus first led him to Greek and biblical studies, and his election in May 1519 as rector of the university was regarded as a triumph for the partisans of the New Learning. It was not, however, until after the Leipzig disputation with Eck that Luther won his allegiance. He accompanied Luther to Worms in 1521, and there was appointed by the elector of Saxony professor of canon law at Wittenberg. During Luther’s stay in the Wartburg Jonas was one of the most active of the Wittenberg reformers. Giving himself up to preaching and polemics, he aided the Reformation by his gift as a translator, turning Luther’s and Melanchthon’s works into German or Latin as the case might be, thus becoming a sort of double of both. He was busied in conferences and visitations during the next twenty years, and in diplomatic work with the princes. In 1541 he began a successful preaching crusade in Halle; he became superintendent of its churches in 1542. In 1546 he was present at Luther’s deathbed at Eisleben, and preached the funeral sermon; but in the same year was banished from the duchy by Maurice, duke (later elector) of Saxony. From that time until his death, Jonas was unable to secure a satisfactory living. He wandered from place to place preaching, and finally went to Eisfeld (1553), where he died. He had been married three times.
See Briefswechsel des Justus Jonas, gesammelt und bearbeitet von G. Kawerau (2 vols., Halle, 1884–1885); Kawerau’s article in Herzog-Hauck, Realencyklopädie, ed. 3, with bibliography.