The bitterness of the opponents of Melancthon was increased by his connection with the "Interim," which was this:
In 1547 a diet was held at Augsburg, and Charles V. required of the Protestants that they should submit the decision of religious contests to the council of Trent. The greater part of the members of the diet consented. But under the pretext of a plague raging in Trent, the Pope issued a bull transferring the council to Bologna. The legates and all the rest of the pa pal party obeyed the pope, but the emperor ordered all of the German bishops to remain at Trent. This virtually dissolved the council at Trent, and the Emperor refused to allow his bishops to go to Bologna. Plainly there could be no council to decide the religious contests, and the action of the diet was nullified.
Now, to keep the matter under control until the difference between the pope and the emperor could be settled, and the council re-assembled, Charles ordered Julius Pilugius, bishop of Nuremberg, Michael Sidonius, a creature of the pope, and John Agricola, of Eisleben, to draw up a formulary which might serve as a rule of faith and worship for both Protestants and Catholics, until the council should be ready to act upon the question. This formulary, from its purpose of being only to cover the interval that should elapse till the council should act, was called the "Interim." But instead of pacifying the contestants, it only led to new difficulties, and involved the whole empire in violence and bloodshed.
Maurice, elector of Saxony, affected to remain neutral in regard to the "Interim," but finally in 1548 he assembled the Saxon nobility and clergy in several conferences, to take counsel about what should be done. In all these conferences, Melancthon was accorded the chief place. He finally gave it as his opinion
"that the whole of the book of 'Interim' could not by any means be adopted by the friends of the Reformation; but declared at the same time that he saw no reason why it might not be adopted as authority in things that did not relate to the essential parts of religion, or in things which might be considered indifferent."
This decision set his enemies all aflame again; and with Flacius at their head, the defenders of Lutheranism attacked Melancthon and the doctors of Wittemberg and Leipsic
"with incredible bitterness of fury, and accused them of apostasy from the true religion." (Mosheim. Ecclesiastical History, cent. xvi, sec. iii, part ii, chap 1, par. 28)
Melancthon and his friends, however, defended his view, and a warm debate followed upon these two points:
1. Whether the points that seemed indifferent to Melancthon were so in reality?
2. Whether in things of an indifferent nature, and in which the interests of religion are not essentially concerned, it be lawful to yield to the enemies of the truth.