Arnold of Brescia was a medieval Italian theologian who was known for his religious and political views that challenged the power of the papacy. Some of the synonyms that are commonly used to describe him include radical, reformer, revolutionary, dissident, and heretic. Arnold's ideas and teachings were considered controversial by the church authorities and even resulted in his excommunication from the church. Despite this, he continued to advocate for his beliefs and gained a following among the people who shared his views. Arnold's legacy continues to influence the study of church history and the political philosophy of Europe.