Final answer:
Salvation, according to Martin Luther, is achieved through faith alone, a key doctrine of the Protestant Reformation that opposed the Catholic Church's teaching of faith combined with good works.
Step-by-step explanation:
According to Martin Luther, one achieved salvation through faith alone, not by good works or purchases of indulgences as asserted by the Catholic Church at the time. Luther's theology emphasized that justification and salvation come by grace through faith, a concept he found in St. Paul's writings - 'The just shall live by faith' (Romans 1:17). This idea of sola fide was one of the key doctrines of the Protestant Reformation and set the stage for a fundamental shift in Christian theology.
Luther's reading of scripture led him to reject the Catholic Church's doctrine that salvation was a result of faith combined with good works. He argued that, since humans are inherently sinful, they can't earn God's grace, which is given freely through faith. This interpretation differed greatly from the Catholic belief system and contradicted the Church's practices, such as selling indulgences, which were claimed to reduce time in purgatory. Luther's views catalyzed the Protestant Reformation and led to the establishment of numerous Protestant denominations.