Caselius, Johann, an eminent German scholar, was born at Göttingen in 1533. He studied first in the schools of Gandersheim and Nordhausen, and afterwards in the universities of Wittenberg and Leipzig, where he received the lessons of Melancthon and J. Camerarius. He then visited Italy, where he continued his studies, and on his return became, in 1563, professor of philosophy and rhetoric in the University of Rostock. During a second journey he made in Italy he received the degree of LL.D. at Pisa, in 1566, and the following year received a patent of nobility from the emperor Maximilian. In 1599 he accepted a professorship in the University of Helmstadt, where he opposed, in union with the Melancthonians, the efforts of ultra Lutheran orthodoxy, principally represented by his colleague, Daniel Hoffmann (q.v.), to proscribe science and philosophy. He was the teacher of George Calixtus (q.v.), and wrote a great number of works, most of which remain unpublished. He died in 1613. See J. Burkhardt's Epistola de Jo. Caselii erga bonus literas meritis ejusque lucubrationum editione (Wittenb. 1707, 4to). — Herzog, Real-Encyklopädie, 2:598.