"What person or event had the greatest impact on western civilization after the fall of Rome and prior to 1715?

"What person or event had the greatest impact on western civilization after the fall of Rome and prior to 1715? Since the answer is subjective (there is no definitively correct answer) you must justify what you write with an adequate number of examples and reasons." The word needed to be used is about 1200words. It is due on July 22, at 11am.Thank you...