Final answer:
Martin Luther believed human beings could reach salvation by faith alone, a key principle of the Protestant Reformation that differed from the Catholic Church's view of salvation through a combination of faith and good works.
Step-by-step explanation:
Martin Luther believed that human beings could reach salvation by faith alone. This concept, also known as the doctrine of justification by faith, was a pivotal aspect of the Protestant Reformation. Luther read the works of St. Paul and interpreted the quote "The just shall live by faith" (Romans 1:17) to mean that God's grace was a gift granted through faith, not earned by good works. Unlike the Catholic Church, which taught that salvation was achieved by a combination of faith and good works, including buying indulgences, Luther asserted that salvation depended entirely upon God and could not be attained through human efforts.
Luther's translation of the Bible into the vernacular and his use of the printing press allowed his ideas to spread widely. His challenge of the Catholic Church's practices led to the posting of the Ninety-five Theses and eventually to his excommunication, which precipitated the expansion of Protestant sects throughout Europe.