Bartholomaeus Arnoldi (usually called Usingen; German: Bartholomäus Arnoldi von Usingen; 1465 – 9 September 1532) was an Augustinian friar and doctor of divinity who taught Martin Luther and later turned into his earliest and one of his personally closest opponents.
[1] Usually called Usingen, after his birthplace, Arnoldi received his master's degree in 1491 and was promoted to the doctorate of divinity in 1514.
For thirty years he filled the chairs of philosophy and theology at Erfurt University, and, with Jodocus Trutfetter,[2] was its leading teacher.
Luther retained an affectionate regard for him and after the Heidelberg Disputation (May 1518) travelled in his company from Würzburg to Erfurt, during which he made efforts to wean him from his ecclesiastical allegiance.
In 1522 he delivered a series of sermons in the cathedral in defence of Catholicism, arraigning the inactivity of the civil and ecclesiastical authorities, and predicted the revolution which came in the German Peasants' War.