We must be careful here. Although we have said that the spiritual authority is the superior and that it may speak into the inferior, we must also be clear that it only speaks to the affairs of the inferior regarding universal principles, since these are its area of expertise. It does not, as we shall note below, provide “technical solutions” to economic or political problems, for these technical and “practical” solutions are the proper domain of political authorities. It is precisely at this point that the Church acknowledges their autonomy. This hierarchical relationship, which carefully combines desire for unity with respect for autonomy, has been called the “Gelasian diarchy,” named after a letter from Pope Gelasius I to Emperor Anastasius in the year 494 AD, when the pope advised the emperor as follows:
“There are two powers, august Emperor, by which this world is chiefly ruled, namely, the sacred authority of the priests and the royal power. Of these that of the priests is the more weighty, since they have to render an account for even the kings of men in the divine judgment.”
Pope Leo XIII affirmed this tradition when he said that “the Almighty…has given the charge of the human race to two powers, the ecclesiastical and the civil, the one being set over divine, and the other over human, things,” but he also made sure to note that there must “exist between these two powers a certain orderly connection which may be compared to the union of the soul and body in man.” No one familiar with the connection between body and soul would suggest that the soul should disregard the activity and function of the body.
 Trans. John S. Ott, Portland State University, from Andreas Thiel, ed., Epistolae Romanorum pontificum genuinae et quae ad eos scriptae sunt a S. Hilaro usque ad Pelagium II., vol. 1 (Brunsberg: Eduard Peter, 1867), Letter no. 12, pp. 349-358.
 ID, 14.