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) 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 which is the purer and the more enduring.
-James Viscount Bryce, The Holy Roman Empire Theory of the Medieval Empire
The War for Christendom 