He was against the Leipzig Interim (1548) with its compromise on some Catholic usages, and was involved in controversies and quarrels; with Georgius Merula, against whom he maintained the need of exorcism in baptism; with Osiander's adherents in the matter of justification; with his colleague, Nicholas von Amsdorf, to whom he had resigned the Eisenach superintendency; with Flacius Illyricus, and others.