The Elector of Saxony was a Lutheran; the Elector Palatine a Calvinist.  The Lutherans believed, that after the consecration of the bread and wine at the sacramental table, the body and blood of Christ were spiritually present with that bread and wine.  This doctrine, which they called consubstantiation, they adopted in antagonism to the papal doctrine of transubstantiation, which was that the bread and wine were actually transformed into, and became the real body and blood of Christ.

The difference between the Calvinists and the Lutherans, as we have before mentioned, was that, while the former considered the bread and wine in the sacraments as representing the body and the blood of Christ, the latter considered the body and the blood as spiritually present in the consecrated elements.  This trivial difference divided brethren who were agreed upon all the great points of Christian faith, duty and obligation.  It is melancholy, and yet instructive to observe, through the course of history, how large a proportion of the energies of Christians have been absorbed in contentions against each other upon shadowy points of doctrine, while a world has been perishing in wickedness.  The most efficient men in the Church on earth, have had about one half of their energies paralyzed by contentions with their own Christian brethren.  It is so now.  The most energetic men, in pleading the cause of Christ, are often assailed even more unrelentingly by brethren who differ with them upon some small point of doctrine, than by a hostile world.

Human nature, even when partially sanctified, is frail indeed.  The Elector of Saxony was perhaps a good man, but he was a weak one.  He was a zealous Lutheran, and was shocked that a Calvinist, a man who held the destructive error that the bread and wine only represented the body and the blood of Christ, should be raised to the throne of Bohemia, and thus become the leader of the Protestant party.  The Elector of Saxony and the Elector of the Palatine had also been naturally rivals, as neighbors, and possessors of about equal rank and power.  Though the Calvinists, to conciliate the Lutherans, had offered the throne to the Elector of Saxony, and he had declined it, as too perilous a post for him to occupy, still he was weakly jealous of his rival who had assumed that post, and was thus elevated above him to the kingly dignity.

Ferdinand understood all this, and shrewdly availed himself of it.  He plied the elector with arguments and promises, assuring him that the points in dispute were political merely and not religious; that he had no intention of opposing the Protestant religion, and that if the elector would abandon the Protestant league, he would reward him with a large accession of territory.  It seems incredible that the Elector of Saxony could have been influenced by such representations.  But so it was.  Averring that he could not in conscience uphold a man who did not embrace the vital doctrine of the spiritual presence, he abandoned his Protestant brethren, and drew with him the Landgrave of Hesse, and several other Lutheran princes.  This was a very serious defection, which disheartened the Protestants as much as it encouraged Ferdinand.