At one point during the First Zurich Disputation, Ulrich Zwingli said the following about Protestant guidelines for religious reform:

The question for Zwingli was no longer one of rejecting the misuse of “good and honorable customs,” as had been the case with Erasmus, but rather of separating human customs from divine ordinances. Zwingli's statement focuses on the foundations of the Protestant attack on medieval piety. Unlike Erasmus, Protestant Reformers drew a sharp distinction between “good” and “evil,” or “true” and “false” worship. This distinction often involved separating the heavenly from the earthly as well.

Protestantism claimed that the medieval Church had fallen into idolatry, and this judgment had a dual perspective. In the first place, as is indicated in Zwingli's argument, a distinction was made between rites of divine origin and humanly devised observances. The externalized cult of medieval Catholicism was attacked as a human institution that was opposed to the worship revealed by God in scripture. In other words, the Church had set itself up as an idol, substituting its own decrees for those of God.

Secondly, the Catholic cult was attacked as improperly directed.