The realistic philosophy, and the needs of a time when the only notion of civil or religious order was submission to authority, required the World-State to be a monarchy; tradition, as well as the continuance of certain institutions, gave the monarch the name of Roman Emperor. A king could not be universal sovereign, for there were many kings: the Emperor must be, for there had never been but one Emperor; he had in older and brighter days been the actual lord of the civilized world; the seat of his power was placed beside that of the spiritual autocrat of Christendom[119]. His functions will be seen most clearly if we deduce them from the leading principle of mediæval mythology, the exact correspondence of earth and heaven. As God, in the midst of the celestial hierarchy, ruled blessed spirits in paradise, so the Pope, His Vicar, raised above priests, bishops, metropolitans, reigned over the souls of mortal men below. But as God is Lord of earth as well as of heaven, so must he (the _Imperator cœlestis_[t]) be represented by a second earthly viceroy, the Emperor (_Imperator terrenus_[120]), whose authority shall be of and for this present life. And as in this present world the soul cannot act save through the body, while yet the body is no more than an instrument and means for the soul's manifestation, so must there be a rule and care of men's bodies as well as of their souls, yet subordinated always to the well-being of that which is the purer and the more enduring. It is under the emblem of soul and body that the relation of the papal and imperial power is presented to us throughout the Middle Ages[121]. The Pope, as God's vicar in matters spiritual, is to lead men to eternal life; the Emperor, as vicar in matters temporal, must so control them in their dealings with one another that they may be able to pursue undisturbed the spiritual life, and thereby attain the same supreme and common end of everlasting happiness. In the view of this object his chief duty is to maintain peace in the world, while towards the Church his position is that of Advocate, a title borrowed from the practice adopted by churches and monasteries of choosing some powerful baron to protect their lands and lead their tenants in war[122]. The functions of Advocacy are twofold: at home to make the Christian people obedient to the priesthood, and to execute their decrees upon heretics and sinners; abroad to propagate the faith among the heathen, not sparing to use carnal weapons[123]. Thus does the Emperor answer in every point to his antitype the Pope, his power being yet of a lower rank, created on the analogy of the papal, as the papal itself had been modelled after the elder Empire. The parallel holds good even in its details; for just as we have seen the churchman assuming the crown and robes of the secular prince, so now did he array the Emperor in his own ecclesiastical vestments, the stole and the dalmatic, gave him a