At the end of City of God 4.28, Augustine makes an eminently sensible remark on the relation, or at least potential relation, between the worship of the true God and civic happiness.
In this section of the work, he argues that the expansion and prosperity of the Roman Empire in previous centuries was not, and could not have been, due to their worship of false gods, though this is what, he says, his interlocutors allege.
He then remarks, not nervously or defensively or as though his comment were subject to doubt, that, had the Romans worshiped the true God as revealed in Jesus Christ, their kingdom would have been “better,” even if their imperial ambitions had been thereby somewhat stifled. And still he keeps his priorities in order: for he grants that, perhaps, they would not have had a better kingdom; still and all, they would have had a better one for eternity.
This passage demonstrates that there can be a kind of political Augustinianism that recognizes the connection between religion and civil society without misplacing its expectations, devaluing the eternal kingdom, or doing the old eschaton-immanentizing two-step. Which is to say, one can consider piety in terms of public welfare, the common weal, without seeking to have the Church dominate the State or turning the former into a puppet of the idolized latter–without, that is, falling prey to the fantasies and dangers of Bob Dylan’s “Utopian hermit monks” who, with their “promises of paradise,” sit “sidesaddle on the Golden Calf.” 1
Chapter 28.—Whether the Worship of the Gods Has Been of Service to the Romans in Obtaining and Extending the Empire.
Therefore such gods, who are propitiated by such honors, or rather are impeached by them (for it is a greater crime to delight in having such things said of them falsely, than even if they could be said truly), could never by any means have been able to increase and preserve the Roman empire. For if they could have done it, they would rather have bestowed so grand a gift on the Greeks, who, in this kind of divine things,—that is, in scenic plays,—have worshipped them more honorably and worthily, although they have not exempted themselves from those slanders of the poets, by whom they saw the gods torn in pieces, giving them licence to ill-use any man they pleased, and have not deemed the scenic players themselves to be base, but have held them worthy even of distinguished honor. But just as the Romans were able to have gold money, although they did not worship a god Aurinus, so also they could have silver and brass coin, and yet worship neither Argentinus nor his father Aesculanus; and so of all the rest, which it would be irksome for me to detail. It follows, therefore, both that they could not by any means attain such dominion if the true God was unwilling; and that if these gods, false and many, were unknown or contemned, and He alone was known and worshipped with sincere faith and virtue, they would both have a better kingdom here, whatever might be its extent, and whether they might have one here or not, would afterwards receive an eternal kingdom.