In 1523, the city of Zurich conducted a public debate that would prove to be a turning point in the Swiss Reformation. Zurich's chief reform champion, Ulrich Zwingli, debated representatives of the Catholic Church. The debate was held before the City Council, which desired to determine whether Zurich would stay faithful to Catholicism or embrace the new reformist ideas sweeping Switzerland and the world. Zwingli emphatically argued that everything taught and practiced in the church should be grounded in Scripture alone. He denounced the church's reliance on traditions with no scriptural basis, arguing that religious authority stemmed from the Word of God rather than the church hierarchy.

Zwingli’s clear and well-reasoned arguments won the day. By the end of the debate, the City Council formally rejected Catholicism and declared that all future preaching in Zurich would be based solely on the Bible. This decision marked Zurich as one of the first cities to officially embrace the Reformation, setting the stage for broader reforms in Swiss society.

Later that year, Zwingli took another bold stance by denouncing the sale of indulgences, a practice where forgiveness of sins was promised in exchange for money. In Switzerland, indulgence sales were spearheaded by a monk named Samson, who relied on this practice to generate significant revenue. Zwingli’s impassioned sermons against indulgences crippled Samson’s efforts and further exposed the corruption within the Catholic Church. This decisive stand strengthened Zwingli’s reputation as a fearless reformer and further solidified Zurich’s commitment to religious reform.