Final answer:
The Council of Trent, convened by Pope Paul III, was a crucial ecumenical council aimed at countering Protestant reforms and reaffirming Catholic doctrines and practices.
Step-by-step explanation:
The meeting of Roman Catholic leaders called by Pope Paul III to rule on doctrines criticized by the Protestant reformers was the Council of Trent. The Council of Trent was an ecumenical council that convened to address the challenges posed by Protestant reformers like Martin Luther and to reaffirm key Catholic doctrines. It was a significant part of the Catholic Reformation and addressed various doctrinal and structural issues within the church.
Highlights included the affirmation of the Doctrine of Merit over the Lutheran concept of justification by faith alone, validation of the seven sacraments, confirmation of the existence of Purgatory, and measures to improve clerical education and to curb abuses such as the selling of indulgences.