During the Renaissance period, thinking shifted from that which closely aligned to the teachings of the Catholic Church to a more humanist perspective. This was in part because of the invention of Gutenburg's printing press, which allowed different types of literature to be published in large quantities. Petrarch was an Italian poet whose work helped to spread the ideas of humanism in Italy and the rest of Europe during the Renaissance.
Also during this time, Martin Luther took a stand against the Catholic Church in Germany. He expressed his concerns with the church, specifically the selling of indulgences. He also suggested that the mass should be in the language of the country where the church is located, rather than solely in Latin. These new ideas and others were the beginning of the Protestant Reformation in Europe.
In both cases, the Renaissance and the Reformation defied the teachings and outlook of the Catholic Church. The Catholic Church lost strength and power in Europe because of these two movements.