- 
  
  Implemented clerical celibacy and opposed lay investiture to strengthen the Church's independence.
- 
  
  Founded the Franciscan Order, emphasizing poverty, humility, and simplicity as a response to the Church's wealth.
- 
  
  Advocated for Bible translation into vernacular languages, challenging the Church's monopoly on scripture interpretation.
- 
  
  Criticized Church corruption and called for reform, inspiring the Hussite movement in Bohemia.
- 
  
  Promoted humanism and criticized
 Church abuses through scholarly works, paving the way for later reformers.
- 
  
  Nailed the 95 Theses (1517) to the Wittenberg door, challenging indulgences and questioning papal authority, sparking the Reformation.
- 
  
  Founded the Jesuits (Society of Jesus) in 1540, focusing on education, missionary work, and countering the Protestant Reformation.
- 
  
  Developed Calvinism, emphasizing predestination and advocating tor a disciplined, theocratic community.