Organized in an attempt to promote unity and reform in the Christian community following the excommunication of Martin Luther, the Council of Trent was one of the most influential councils in the history of the Roman Catholic Church. Spanning the reign of three Popes from 1545 to 1563, the council issued a number of decrees in which it established dogma that would serve as the foundation of modern-day Catholicism. In these decrees, the council asserted the Catholic belief in transubstantiation, defined Mass as a sacrifice in remembrance of Christ, condemned Protestant beliefs that it defined as heresy, and ruled against Martin Luther’s belief in justification “by faith alone.” Confirmed by Pope Pius IV in 1564, these decrees—and many others—marked a major victory in the Counter-Reformation movement, and restored the faith of many in the authority of the Catholic Church. (Image Source: Unknown [Public Domain], via Wikimedia Commons, https://commons.wikimedia.org/w/index.php?curid=1148806)