Final answer:
Martin Luther asserted that salvation is a free gift from God granted through faith alone ('sola fide'), challenging the Catholic Church's doctrine that good works and indulgences contribute to salvation. Luther's Ninety-five Theses and the translation of the Bible into German were pivotal in the formation of Protestantism and its beliefs.
Step-by-step explanation:
Martin Luther's Concept of Salvation
Martin Luther, a central figure in the Protestant Reformation, challenged the prevailing Catholic doctrine with his assertion that salvation was a free gift from God and could not be earned through good works or the purchase of indulgences. Luther's study of the Bible, especially the writings of St. Paul, led him to the conclusion that faith alone ('sola fide') was the means to salvific justification. This stance directly opposed the Catholic Church's teaching that salvation was achieved through a combination of faith and good works, including the buying of indulgences.
Impact of Luther's Teachings
Luther's translation of the Bible into German and his Ninety-five Theses, which were openly critical of the Church's practices, were instrumental in forming the basis of Protestantism. The doctrine of justification by faith became a cornerstone of Protestant belief, significantly distinguishing it from Catholicism. Luther's ideas contributed to an understanding that divine grace and mercy are the sole arbitrators of human salvation, with no transactional actions such as indulgences influencing this sacred exchange.