Omid Safi is Professor of Islamic Studies at the University of North Carolina at Chapel Hill where he specializes on Islamic mysticism (Sufism), contemporary Islamic thought and medieval Islamic history. He has served on the board of the Pluralism project at Harvard University and is the co-chair of the steering committee for the Study of Islam at the American Academy of Religion.

Professor Safi is recognized as a leader of the progressive Muslim debate. Professor Safi's book Progressive Muslims (2003) contains a diverse collection of essays by and about "progressive" Muslims. Professor Safi was one of the co-founders of the Progressive Muslim Union (PMU-NA). He resigned from PMU in 2005, but he continues to support progressive interpretations of Islam outside of PMU.

 Martin Luther (help·info) (10 November 1483 – 18 February 1546) was a German monk, priest, professor of theology and iconic figure of the Protestant Reformation. He strongly disputed the claim that freedom from God's punishment for sin could be purchased with money. He confronted indulgence salesman Johann Tetzel with his Ninety-Five Theses in 1517. His refusal to retract all of his writings at the demand of Pope Leo X in 1520 and the Holy Roman Emperor Charles V at the Diet of Worms in 1521 resulted in his excommunication by the pope and condemnation as an outlaw by the Emperor.

Luther taught that salvation is not earned by good deeds but received only as a free gift of God's grace through faith in Jesus Christ as redeemer from sin. His theology challenged the authority of the Pope of the Roman Catholic Church by teaching that the Bible is the only source of divinely revealed knowledge and opposed sacerdotalism by considering all baptized Christians to be a holy priesthood. Those who identify with Luther's teachings are called Lutherans.