We now turn to chapter three.
The Secularization of Roman History
Augustine tended to employ the rhetorical device of “dramatic contrasts” to “express[…] his ideas”, because of the two-poled organization of much of his thought.  Thus, from early on in his writings there were “two ‘kinds’ of men […] defined in terms of two communities they were said to belong to”, the impious and earthly on the one hand, and those of God on the other. These two types were soon “transposed into a social key and represented in the image of two societies or cities, in their turn typified by the biblical images of Babylon and Jerusalem.”  Augustine hints that “civil society” may be identified with the earthly city, Babylon — but these are merely hints, and “on the periphery”. After the sack of Rome in A.D. 410, however, Augustine was prompted by the criticisms of a pagan Volusianus to write the City of God (CoG). Volusianus, together with other pagan Romans, was “blaming the disaster [of Rome’s sack] on the substitution of the Christian religion for the old cult” . What resources could Augustine draw upon in his reply?
One Christian tradition concerning the Roman Empire can be found in figures such as Melito of Sardis and Origen of Alexandria; Melito “thought that the unification of the orbis Romanus under the emperors was geared under God’s providence to the propagation of the Gospel”, while Origen thought that the “final establishment of a single polity was something” to look “forward [to] as a possibility for the divine saving work which heals all fragmentation.”  From this second position “[i]t was only a short step” for Eusebius, Origen’s “disciple”, “to see the Constantinian monarchy as part of God’s plan for consummating this unification.”
Then there is the tradition rooted in the Revelation of Jesus Christ to John (usually simply “Revelation“), which paints the empire as the Beast. Likewise, Hippolytus of Rome saw “the Roman Empire [as] a satanic imitation of the kingdom of Christ: it made the same claims to unity, to universality and to endless duration.” 
After the passing of the persecutions, and the arrival of Constantine, most Christians were “quick to change their minds” about Rome and many “referred” some traditionally-messianic verses to Constantine. So for Eusebius, “Constantine brings to a fulfilment what God himself had prepared  in Christ and Augustus: he brings about the unification of the world in a single harmonious order, one Empire devoted to the worship of the one true God.” Eusebius “stops short” of saying that Constantine’s kingdom is simply Christ’s. The emperor is “the image of the Logos”, however, and his Empire is an image of Christ’s. Church and Empire are “twin roots of blessing”. Among fourth-century writers, however, the Empire “had almost universally become a part of the sacred history”, East and West. Prudentius could ask Christ to “Grant” […] to your Romans, that the City become Christian”.  Even after 410, Orosius can write similarly.
For Augustine, after 410, many of the texts that had been “standard repertory of the Eusebian Rome-theology” no longer had any “reference to the Empire” in his interpretation.  Jerome and Ambrose focused on the significance of the Empire for the Apostles’ mission, Augustine on the dispersion of the Jews. “Roman world-domination, when achieved, is not a preparation for the preaching of Christ’s kingdom, but the achievement of ‘the new Babylon’.”  In repudiating the Theodosian “mirage” , Augustine wasn’t repudiating “a passing mood of elation” , but the then-near-universal thought of the churches. Roman history is no longer interpreted “in prophetic categories”.  “The Christianization of the Roman Empire is as accidental to the history of salvation as it is reversible”.  Even Orosius, by contrast, saw the Christian Empire (after 410) as definitive, as having superseded the age of persecutions, a mark of progress not to be reversed until the last days of Antichrist. By contrast, Christianization loses religious significance for Augustine. Empire is dispensable.  This is because it
has become no more than a historical, empirical society with a chequered career, whose vicissitudes are not to be directly correlated with the favour of the gods, pagan or Christian, given in return for services rendered. It is theologically neutral. 
Christians could avoid thinking about the Empire and about human societies. Those who did think about it had the Eusebian and Hippolytan options (the Donatists took the latter). “Augustine followed neither.”  His unique position is a result of this rejection.
Christianization was not a break in Roman history. Indeed, Augustine’s letters reveal how Roman he was, both in his civic administrative involvements as a bishop, and his culturing as a learned man. “His tone is often unmistakably and authentically Roman, and full of legitimate pride in the stock exempla of Roman virtue”.  (See CoG V.15, for his praise of the virtues that went into the foundation of Rome.) And yet, “the limited, earthbound and temporary character of the reward”  of the virtues that founded Rome have their end in this world, and so are “neutral. [The “Roman achievement”] is neither to be repudiated as Satanic, nor to be endorsed as holy, except in virtue of the ultimate allegiances mobilised in this kind of endeavour.” This “indeterminateness” characterizes all human achievement. Belonging to the state does not mean belonging to the earthly city. The earthly city cannot be equated with the state, any more than the Church can be equated with the heavenly city.  Both institutions will have members of both cities.
It is not membership in earthly, secular groups (Church or state) that define membership in either city, but the character of an individual’s loves: “‘two loves have built the two cities: self-love in contempt of God the earthly city, love of God in contempt of self the heavenly”.  Thus, “Rome can only be called the earthly city in a secondary or derivative sense, in so far as the Empire is a society organised around loyalties with no positive relation to God.”  Rome is a visible society, but neither the earthly city nor the heavenly city are visible, empirical societies in the saeculum, in this age. Only eschatologically are they separated, and true societies. Nonetheless, since a city is a society bound together from “a multitude of individuals”  according to common loves, however divisive those loves may be in the end, these two groups can be spoken of as cities. Yet “[h]ere and now the two cities melt into one another”. Only at the end of history will they be “disentangled”. All history is a conflict between these two cities, these two loves.
The political sphere cannot be simply assimilated to the earthly city, for it is fully participated in by members of the heavenly city, although these participate for ends beyond the polis. And so, “the sphere in which human kingdoms, empires and all states have their being is radically ambiguous, and all social institutions and human groupings are radically infected with this ambiguity.” Both cities suffer the same things, and use the same things, but not for the sake of the same ultimate hopes or loves. Before the end, the two cannot be separated. The history of the Church is, thus, also no longer part of sacred history.  The “area of indeterminacy between the two cities” where they share proximate, worldly goals for different principles is “the theological locus in which [Augustine] places politically organised society.” 
“Following hints he found in Cicero”, Augustine made true justice a prerequisite for a true community, for a res publica. Heightening the meaning of “justice” into the expansive biblical sense, it becomes clear that “the requirements of real justice are met only in the City of God”  in which
God alone rules by grace […] in whose members the body is subject to the soul, the passions to reason, in observance of the right order
and in which the “whole multitude” lives by faith-working-through-love. Alternatively, a “people” might more ordinarily be spoken of as
a multitude of reasonable beings, united in agreement over the things they love
which would serve well enough as a description of mixed political societies in the blended saeculum. No mention of “true justice”, only of coordinated loves. Now, a thing can be loved for its own sake, as an end in itself, or for the sake of some higher good. Unsurprisingly, “[h]uman excellence”, in the end, “is realised in achieving a  balanced perspective over the whole range of ‘loves’.” Loves must be ordered according to the relative worth of what is loved, or else disorder –vice– occurs. (So covetousness ends up being the inordinate love of money above justice, etc.) As with one’s loves, so with one’s enjoyments. Nothing but God can “serve as a resting-place” for full human enjoyment; “to seek to ‘enjoy’ anything else is to be retarded in one’s journey or diverted from its true destination.”  The two cities are concerned with the ultimate end they seek to enjoy, and to which they subordinate all other loves and enjoyments. 
All people use the things of this world, but not all use them for the same ends — some use worldly things for worldly ends, some for eternal ends. “Peace” is the rest of longing, arrival at one’s loves. It has many levels. “[T]he restricted sphere to which the earthly city confines its concerns is that of ‘temporal peace'”; security, order, material needs. This earthly peace is a “common concern to all”, and is “valued and ‘loved’ by both”  cities, yet for “differing structures of motivation.”  The agreement of many individuals to value certain things does not mean weighing the value of those valued things identically. In this sense, the state is pluralistic. Also, this gives politics “a considerable degree of autonomy”, effectively pushing religious commitments
outside of the sphere of political discourse. The only links between the realm of politics and the realm of faith and morals were now those which existed inwardly, in the way in which individuals’ valuations are structured. 
This consensual sphere of proximate, worldly loves should not be thought to permit the commanding of injustice — neither impiety nor injustice can be compelled in this sphere. This is so because “the saeculum [… is not] a no-man’s land between the two cities, but [is] their temporal life in their interwoven, perplexed and only eschatologically separable reality.”  The heavenly city loves this earthly peace, too.