The average man of the Middle Ages lived a very simple and uneventful life. Even if he was a free citizen, able to come and go at will, he rarely left his own neighbourhood. There were no printed books and only a few manuscripts. Here and there, a small band of industrious monks taught reading and writing and some arithmetic. But science and history and geography lay buried beneath the ruins of Greece and Rome. Whatever people knew about the past they had learned by listening to stories and legends. Such information, which goes from father to son, is often slightly incorrect in details, but it will preserve the main facts of history with astonishing accuracy. After more than two thousand years, the mothers of India still frighten their naughty children by telling them that "Iskander will get them," and Iskander is none other than Alexander the Great, who visited India in the year 330 before the birth of Christ, but whose story has lived through all these ages. The people of the early Middle Ages never saw a textbook of Roman history. They were ignorant of many things which every school-boy to-day knows before he has entered the third grade. But the Roman Empire, which is merely a name to you, was to them something very much alive. They felt it. They willingly recognised the Pope as their spiritual leader because he lived in Rome and represented the idea of the Roman super-power. And they were profoundly grateful when Charlemagne, and afterwards Otto the Great, revived the idea of a world-empire and created the Holy Roman Empire, that the world might again be as it always had been. But the fact that there were two different heirs to the Roman tradition placed the faithful burghers of the Middle Ages in a difficult position. The theory behind the mediaeval political system was both sound and simple. While the worldly master (the emperor) looked after the physical well-being of his subjects, the spiritual master (the Pope) guarded their souls. In practice, however, the system worked very badly. The Emperor invariably tried to interfere with the affairs of the church and the Pope retaliated and told the Emperor how he should rule his domains. Then they told each other to mind their own business in very unceremonious language and the inevitable end was war. Under those circumstances, what were the people to do, A good Christian obeyed both the Pope and his King. But the Pope and the Emperor were enemies. Which side should a dutiful subject and an equally dutiful Christian take? It was never easy to give the correct answer. When the Emperor happened to be a man of energy and was sufficiently well provided with money to organise an army, he was very apt to cross the Alps and march on Rome, besiege the Pope in his own palace if need be, and force His Holiness to obey the imperial instructions or suffer the consequences.