How was Martin Luther's doctrine of "justification by faith alone" significant in world history?
Luther’s doctrine was important in world history for both institutional reasons and individual reasons.
In terms of institutions, Luther’s doctrine helped to break up the Roman Catholic Church. This was, of course, a hugely momentous event in world history. It caused, for example, the religious wars that wracked Europe for a long time after the Protestant Reformation. In this way, his doctrine was important because it created a situation in which there were multiple Christian faiths that sometimes came into conflict with one another.
But Luther’s doctrine was also important on the individual level. His doctrine was a more democratic doctrine than that of the Catholic Church. It essentially put all individuals on the same level. It said that no one needed someone else to tell them how to behave so as to be saved. This helped to bring about a real change in the way people thought about themselves and their place in society. It helped to bring about a more democratic way of thinking in which people did not see themselves as part of a preordained hierarchy but, rather, as individuals who were just as important as any other individuals. We can argue that this change helped to lay the foundation for the more democratic world that we live in today.