Nicene and Post-Nicene Fathers, Vol. II:
City of God: Chapter 17

Chapter 17.—What Produces Peace, and What Discord, Between the Heavenly and Earthly Cities.

But the families which do not live by faith seek their peace in the earthly advantages of this life; while the families which live by faith look for those eternal blessings which are promised, and use as pilgrims such advantages of time and of earth as do not fascinate and divert them from God, but rather aid them to endure with greater ease, and to keep down the number of those burdens of the corruptible body which weigh upon the soul.  Thus the things necessary for this mortal life are used by both kinds of men and families alike, but each has its own peculiar and widely different aim in using them.  The earthly city, which does not live by faith, seeks an earthly peace, and the end it proposes, in the well-ordered concord of civic obedience and rule, is the combination of men’s wills to attain the things which are helpful to this life.  The heavenly city, or rather the part of it which sojourns on earth and lives by faith, makes use of this peace only because it must, until this mortal condition which necessitates it shall pass away.  Consequently, so long as it lives like a captive and a stranger in the earthly city, though it has already received the promise of redemption, and the gift of the Spirit as the earnest of it, it makes no scruple to obey the laws of the earthly city, whereby the things necessary for the maintenance of this mortal life are administered; and thus, as this life is common to both cities, so there is a harmony between them in regard to what belongs to it.  But, as the earthly city has had some philosophers whose doctrine is condemned by the divine teaching, and who, being deceived either by their own conjectures or by demons, supposed that many gods must be invited to take an interest in human affairs, and assigned to each a separate function and a separate department,—to one the body, to another the soul; and in the body itself, to one the head, to another the neck, and each of the other members to one of the gods; and in like manner, in the soul, to one god the natural capacity was assigned, to another education, to another anger, to another lust; and so the various affairs of life were assigned,—cattle to one, corn to another, wine to another, oil to another, the woods to another, money to another, navigation to another, wars and victories to another, marriages to another, births and fecundity to another, and other things to other gods:  and as the celestial city, on the other hand, knew that one God only was to be worshipped, and that to Him alone was due that service which the Greeks call λατρεία, and which can be given only to a god, it has come to pass that the two cities could not have common laws of religion, and that the heavenly city has been compelled in this matter to dissent, and to become obnoxious to those who think differently, and to stand the brunt of their anger and hatred and persecutions, except in so far as the minds of their enemies have been alarmed by the multitude of the Christians and quelled by the manifest protection of God accorded to them.  This heavenly city, then, while it sojourns on earth, calls citizens out of all nations, and gathers together a society of pilgrims of all languages, not scrupling about diversities in p. 413 the manners, laws, and institutions whereby earthly peace is secured and maintained, but recognizing that, however various these are, they all tend to one and the same end of earthly peace.  It therefore is so far from rescinding and abolishing these diversities, that it even preserves and adopts them, so long only as no hindrance to the worship of the one supreme and true God is thus introduced.  Even the heavenly city, therefore, while in its state of pilgrimage, avails itself of the peace of earth, and, so far as it can without injuring faith and godliness, desires and maintains a common agreement among men regarding the acquisition of the necessaries of life, and makes this earthly peace bear upon the peace of heaven; for this alone can be truly called and esteemed the peace of the reasonable creatures, consisting as it does in the perfectly ordered and harmonious enjoyment of God and of one another in God.  When we shall have reached that peace, this mortal life shall give place to one that is eternal, and our body shall be no more this animal body which by its corruption weighs down the soul, but a spiritual body feeling no want, and in all its members subjected to the will.  In its pilgrim state the heavenly city possesses this peace by faith; and by this faith it lives righteously when it refers to the attainment of that peace every good action towards God and man; for the life of the city is a social life.