With regard to the Sacraments Luther and Zwingli agreed that they were only signs of grace, though in the explanation of this view Zwingli was much more extreme, because much more logical, than Luther. Believing as he did that justification depended upon faith alone, he contended that the Sacraments were mere ceremonies by which a man became or showed himself to be a follower of Christ. They were devoid of any objective virtue, and were efficacious only in so far as they guaranteed that the individual receiving them possessed the faith necessary for justification. But it was principally in regard to the Eucharist that the two reformers found themselves in hopeless disagreement. Had Luther wished to be consistent he should have thrown over the Real Presence as well as Transubstantiation, but the force of tradition, the fear that any such teaching would arouse the opposition of the people, and the plain meaning of the texts of Scripture forced him to adopt a compromise. "Had Doctor Carlstadt," he wrote, "or any one else been able to persuade me five years ago that the sacrament of the altar is but bread and wine he would, indeed, have done me a great service, and rendered me very material aid in my efforts to make a breach in the Papacy. But it is all in vain. The meaning of the texts is so evident that every artifice of language will be powerless to explain it away." He contended that the words "This is My body and This is My blood" could bear only one meaning, namely, that Christ was really present, but while agreeing with Catholics about the Real Presence of Christ in the Eucharist, he rejected the doctrine of Transubstantiation, maintaining in its place Consubstantiation or Impanation. Though Luther insisted so strongly on the Real Presence, it is not clear that in the beginning he had any very fixed views on the subject, or that he would have been unwilling to change any views he had formed, were it not that one of his lieutenants, Carlstadt, began to exercise his privilege of judgment by rejecting the Real Presence. Such an act of insubordination aroused the implacable ire of Luther, who denounced his former colleague as a heretic, and pursued him from Wittenberg and Jena, where he had fled for refuge. In the end Carlstadt was obliged to retire to Switzerland, where his doctrine found favour with the Swiss reformers.