How did we arrive with Catholics and Protestants?

Catholics and Protestants split with the 95 Theses issued by Martin Luther in 1517. Martin Luther, a Catholic professor, had become disturbed by some church practices, particularly the selling of indulgences, essentially the marketing of God’s forgiveness of sins for a price. The money in theory was going to be used for repairing the facilities of St. Peter’s basilica in Rome. As repulsive as the idea of indulgences was, it came out of the Catholic tradition that salvation was a matter of God’s work (forgiveness) and our work (good deeds); in other words, God did His part and I did my part to ensure my salvation. Luther instead taught that salvation and, thus, eternity in heaven, is not earned by good deeds but is received only as a free gift of God’s grace through faith in Jesus Christ as redeemer from sin. He challenged the traditional authority of the Pope by teaching that the Bible is the only source of divinely revealed knowledge from God, and he opposed sacerdotalism (the belief that men required the intervention of priests, that only priests could commune directly with God). He believed the Bible taught that all baptized Christians were in and of themselves a holy priesthood, with no need for mediation apart from that already accomplished by Jesus Christ. It was however the practice of selling indulgences that initially moved Luther to action. The theology behind it was that faith alone cannot justify man; justification rather depends only on such faith as is active in charity and other good works. The benefits of such good works could be obtained by donating money to the church. On October 31, 1517, Luther wrote to his bishop protesting this practice. He enclosed in his letter a copy of his “Disputation of Martin Luther on the Power and Efficacy of Indulgences,” which later came to be known as The Ninety-Five Theses. It is not thought that Luther intended to confront the church; rather, he saw his protest as a scholarly objection to church practices. However, there could be seen a sense of rebellion in his writing; Thesis 86, for example, asked, “Why does the pope, whose wealth today is greater than the wealth of the richest Crassus (a Roman general at the time of the Republic who is considered one of the richest men of history), build the basilica of St. Peter with the money of poor believers rather than with his own money?” He insisted that, since forgiveness was God’s alone to grant, those who claimed that indulgences cleansed buyers from all punishments and granted them salvation were in error. By January 1518, friends of Luther had translated his 95 Theses from Latin into German and printed and widely copied them, making this dispute one of the first in history to be aided by the printing press. Within two weeks, copies had spread throughout Germany; within two months, they had spread throughout Europe. The revolution that became the Protestant Reformation was begun.
Luther’s change of heart had been inspired by the period from 1510-20, when he lectured on the Psalms, Hebrews, Romans and Galatians. As he studied these books of the Bible, he came to view the use of terms such as penance and righteousness as prescribed by the Catholic Church in new ways. He became convinced that the church was corrupt in its ways and had lost sight of what he saw as several of the fundamentals of Christianity. The most important for him was the doctrine of justification—God’s act of declaring a sinner righteous, “not guilty”—by faith alone through God’s grace. He began to teach that salvation or redemption is a gift of God’s grace, attainable only through faith in Jesus as the Christ. He wrote, “This one and firm rock, which we call the doctrine of justification, is the chief article of the whole Christian doctrine, which comprehends the understanding of all godliness.” He came to understand justification as entirely the work of God (Ephesians 2:8-10). Against the teaching of his day that the righteous acts of believers are performed in cooperation with God, Luther wrote that Christians receive such righteousness entirely from outside themselves; that righteousness not only comes from Christ but actually is the righteousness of Christ, imputed to Christians (rather than infused into them) through faith. He wrote, “That is why faith alone makes someone just and fulfills the law. Faith is that which brings the Holy Spirit through the merits of Christ.” For Luther, faith was a gift from God. He wrote that Jesus Christ died for our sins and was raised again for our justification (Romans 3:24-25). He alone is the Lamb of God who takes away the sins of the world (John 1:29), and God has laid on Him the iniquity of us all (Isaiah 53:6). All have sinned and are justified freely, without their own works and merits, by His grace, through the redemption that is in Christ Jesus, in His blood (Romans 3:23-25). This is necessary to believe. This cannot be otherwise acquired or grasped by any work, law or merit. Therefore, it is clear and certain that faith alone justifies us.