from: James Viscount Bryce, The Holy Roman Empire (1864), ch 7, "Theory of the Mediaeval Empire," pp. 102-105. Note that Bryce was an English gentleman and as openly anti-Catholic in his writings as he was contemptuous of the Hapsburgs, the last dynasty to preside over the Holy Roman Empire. Bryce was also very interested in presenting the Holy Roman Empire as an autocratic "world-state" to which all subjects must prostrate themselves, in contrast to a constitutional government which Bryce and his audience supposed would keep men free, a bias to which most people would subscribe today. Nonetheless, if we keep these and other biases in mind, Bryce’s work remains delightful in many ways, and there is no similar modern account of the Holy Roman Empire in English. Read and enjoy, but do not necessarily believe all that he says.
"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 continued existence of a part of the ancient 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 universal, 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. His functions will be seen most clearly if we deduce them from the leading principle of mediaeval mythology, the exact correspondence of earth and heaven. As God, in the midst of the celestial hierarchy, rules blessed spirits in Paradise, so the Pope, his vicar, raised above priests, bishops, metropolitans, reigns over the souls of mortal men below. But as God is Lord of earth as well as of heaven, so must he (the Imperator coelestis) be represented by a second earthly viceroy, the Emperor (Imperator terrenus), 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 element 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. 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 view of this object his chief duty is to maintain peace in the world, while towards the Church his position is that of Advocat or Patron .... The functions of advocacy are twofold: at home to make the Christian people obedient to the priesthood, and to execute priestly decrees upon heretics and sinners; abroad to propagate the faith among the heathen, nor sparing to use carnal weapons. Thus does the Emperor correspond in every point to his counterpart 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. ... Thus the Holy Roman Church and the Holy Roman Empire are one in the same thing, seen from different sides; and Catholicism, the principle of the universal Christian society, is also Romanism; that is, rests upon Rome as the origin and type of its universality; manifesting itself in a mystic dualism which corresponds to the two natures of its Founder. As divine and eternal, its head is the Pope, to whom souls have been entrusted; as human and temporal, the Emperor, commissioned to rule men’s bodies and acts."