Martin Luther (1483-1546) was a German theologian whose writings instigated the Protestant Reformation in the 16th century. Luther became an Augustinian friar in 1505 and was ordained two years later. In 1510 he visited Rome and was appalled at the level of corruption there. He became increasingly disillusioned with the Church and in 1517 he published Ninety-Five Theses, a scathing attack on abuses within the Church. His writings called into question some of the fundamental tenets of Roman Catholicism and resulted in the schism between Catholicism and Protestantism. He is one of the most influential figures in the history of Christianity.