Many members of the Protestant church today do not understand properly their origins and the nature of their predecessors "protest" against the Roman Catholic Church. When asked about the respective differences, they may respond with some stereotypical answers such as, "I don't worship Mary," "I believe in justification by faith, not works," or "The bread and wine of the Lord's supper don't really turn into the body of Jesus." In this lesson, Dr. Sproul explains the real, serious points of doctrine at stake during Martin Luther's timeframe and the Reformation, paying careful attention to the doctrine of justification and its place in Roman Catholic thought.