In the time and place we call the later Roman Empire, Augustine, bishop of Hippo Regius (now Annaba in Algeria), wrote a very long book, de civitate Dei: in English, City of God. It took him about 13 years, from 412-13 to 426–27, because he was always busy with pastoral work and with other more urgent debates. For centuries Augustine’s writings had a major influence on western Christian theology. City of God was especially revered, and before the age of print there were many manuscript copies; but then as now, few people read the whole, and the book was often misinterpreted. City of God is not political theory, or a thought-experiment like the Republic of Plato; it does not discuss the best form of the state or seek to establish the city of God on earth. It is about worshipping the true God. But it is relevant for our theme because it challenges the concepts of nation, state and empire.

City of God is concerned with empire because, in Augustine’s time, the Roman Empire was thought to be the greatest and longest-lasting the world had ever known, and many people believed that Rome’s empire was owed to Rome’s gods. They feared that the Christian emperor Theodosius I offended the gods and endangered the empire when, in 391–92, he banned the public and private cult of the gods of Rome; and they thought their point was proved when two decades later, in 410, a war-band of barbarian Goths spent three days looting the city of Rome. The imperial court had moved to other cities, and some emperors never visited Rome, but Rome was still the symbolic capital of empire.

Important refugees made the short sea-crossing from Italy to Carthage, the capital city of the region which Romans called Africa. A senior Roman official, himself a Christian, told Augustine how one of them, making familiar objections to Christian belief, added a claim that Christianity and empire are not compatible: ‘He says, moreover, that Christ’s preaching and teaching are wholly incompatible with our traditions of government. Christ taught (it is agreed) that we ought to return no one evil for evil, and to offer the other cheek to someone who hits us, and to give our cloak to someone who insists on taking our tunic, and to go twice the distance with someone who requisitions our service. All these, he affirms, are contrary to our traditions of government. For who would endure to have something taken from him by an enemy, or would not wish to repay evil, by right of war, to the raider of a Roman province? He thinks that all these concerns can be added to the question at issue – whether Christianity is a coherent system of belief – in that under Christian emperors, who strongly maintain the Christian religion, it is evident (even if he himself is silent on this) that such great evils have befallen the commonwealth.’ City of God began as Augustine’s response to complaints which were prompted by the shock of the Gothic raid on Rome. He challenged the claims of his opponents that the Roman Empire had an exceptional god-given destiny. He knew that they did not recognise the authority of Judaeo-Christian scripture, so he deployed the classical Latin authorities they did acknowledge, and he wrote in the classical Latin which was the sign of education. He called his book ‘city of God’, de civitate Dei, in accordance with language used in scripture; but scripture more often refers to the ‘kingdom’ or the ‘people’ of God, and Augustine’s interpretation of a civitas is Roman. The Latin word civitas means a gathering of cives, citizens. They may live in the built environment of a city (urbs), but in Roman tradition a civitas extends beyond the town to include all its citizens, wherever they live in its territory. Manuscript illustrations show the city of God walled and towered like other cities, but Augustine’s city has no walls. It is more than a cosmopolis, a city which has all the world as its citizens. It transcends space and time and even physical being, for its citizens are all the rational beings who love God and want to do God’s will, and rational beings include angels, immortal spiritual beings, as well as humans. The opposite of the city of God is the earthly city, which has as its citizens all the angels and humans who love themselves and want their own way. Augustine took from the Bible two symbols of these two cities: Jerusalem, whose Hebrew name means ‘vision of peace’, and Babylon, like Rome the name of a city and of an empire, the power which had held God’s people Israel captive in exile from their homeland. Roman writers of history thought that Babylon was the first great empire, and that its king, Ninus, was the first in human history to make an unprovoked attack on his neighbours. According to Judaeo-Christian scripture, Babylon was home to the Tower of Babel, the image of human arrogance. Augustine thought that ‘babel’ meant ‘confusion’: it is characteristic of the earthly city, he said, that there is no consistent moral or religious teaching, only a babble of conflicting voices. The book of Genesis tells how, after the great flood, everyone still spoke the same language. Coming to a plain where they found clay for bricks and bitumen for mortar, they planned to build a city and a tower with its top in the heavens, so that they should not be scattered over the earth. But God confused their language so that they could not understand each other, and scattered them over the earth. That was the origin of nations, the gentes (peoples) with separate countries and languages, where the gentiles live and worship their own gods.

Cities, earthly or heavenly, are their citizens: that is what a civitas is. In 410, Augustine’s congregation was shocked by reports of slaughter and looting at Rome, which for them was the city of the great saints Peter and Paul, of churches and martyr-shrines. But Augustine insisted in his preaching that Rome was the Romans, the citizens, the individual human beings who together are the city. Rome is not the built environment, the walls and tower-blocks made of stone and timber, which people put together and people pull apart; some day, all such cities will fall into ruin. The brief distress inflicted by the Goths must be kept in perspective. Far worse has happened in Roman history, and Rome has not been wiped off the face of the earth like Sodom and Gomorrah, the ‘cities of the plain’ whose destruction is narrated in the book of Genesis. (Recent archaeology confirms that the Goths did not do serious damage to Rome.) In Augustine’s view, suffering must always be interpreted as deserved punishment for sin, or as a wake-up call. The important fact is the relationship to God of individual human beings, which is the criterion of citizenship in one or other of Augustine’s two cities. Citizenship depends on what you love: God, or yourself. It does not depend, as was usual in the classical world, on descent or on ability to serve the state with property or military service.

The Roman Empire was an empire of cities, not of independent or subject or allied nations. Augustine used interchangeably the words for peoples and kingdoms, nations and ethnic groups, but citizenship was central to his argument and to his own experience. In the classical world, Roman citizenship was distinctive because it coexisted with citizenship of a home town. When Rome began to conquer other territories, centuries before Augustine’s time, Roman citizenship was a privileged status, achieved by only a few of those who were not Roman by descent. But large-scale grants of citizenship became more common, and from 212 AD all free-born inhabitants of the Roman Empire were citizens. This was not a colonial empire exploiting the resources of subject territories. The Roman Empire was not quite a free trade area, because there were local taxes and harbour dues, but its citizens had freedom of movement. They could travel where they wished, as economic migrants or tourists or refugees from barbarian invasion, and they would find the same basic structures of government and laws, and people who shared a common culture and education and language – Latin in the west and Greek in the east. Rome had long ago defeated the Carthaginian empire, but in the later Roman Empire Carthage was the capital city of a flourishing province. It was reasonable for Augustine to ask, ‘what difference does it make, in relation to security and morality which are the true marks of status, who conquers and who is conquered?’ Everyone, he pointed out, is liable for the same taxes, is subject to the same laws, has access to the same education; there are Roman senators who have never seen Rome.

The citizens of Augustine’s two cities on earth have the same language and culture and institutions. Everybody belongs to one or the other, but we do not know who belongs to which, and we will not know, even about ourselves, until, at the Last Judgement, God separates the two cities which are intermixed in this life. Even among the enemies of the city of God, there may be some of its future citizens; even among those who come to church and share the sacraments, there may be citizens of the earthly city. It depends on what they love. A high-ranking imperial official, exercising his power with all the trappings of office, may be motivated by love for God and for neighbour; a member of the Christian clergy, engaged in pastoral work and preaching, may be motivated by desire for praise. Augustine doubted himself: when a sermon was greeted with shouts of ‘Bravo!’, did he rejoice that the love of God had touched his people, or was he pleased by the reception of his sermon? We do not know who belongs to which city, so we cannot simply equate the earthly city with the state and the city of God with the church, unless ‘the church’ means the blessed company of all faithful people, not the church as an institution. But Augustine’s readers have sometimes lost sight of this basic principle. When Augustine spoke of ‘the city of God on earth’, he meant what he called the peregrina civitas. This phrase is often translated as the ‘pilgrim city’, with the focus on travel to a destination, but in classical Latin a peregrinus is not a pilgrim but someone who is away from home, as a traveller or an exile or a foreigner; peregrina civitas is a contradiction, because a peregrinus is a resident alien. The city of God on earth consists of those citizens of God’s city who, in this mortal life, are away from their true home in heaven. Some readers of Augustine tried instead to find ways of transforming the earthly city into the city of God on earth. Augustine said: ‘There is no true justice except in the res publica whose founder and ruler is Christ.’ Res publica, literally ‘common wealth’ or ‘public property’ or ‘public concern’, is notoriously difficult to translate. ‘State’, ‘government’ and ‘country’ are all possible, though with the warning that ‘state’ as distinct from ‘people’ is not a classical concept. Augustine borrowed a definition from Cicero, one of the greatest classical authorities, who suggested that a res publica is ‘public property’, that is, the property of a people; and a people is not a random assemblage, but a gathering united in agreement on justice and utility. Augustine argued that, on this definition, Rome never was a res publica, because Rome’s own historians showed that Rome was founded in fratricide and rape and was always beset by injustice and civil strife. So, there was no people united in agreement on justice and utility, and where there is no people there is no res publica. Without justice, a social contract is not enough: even gangs, latrocinia, have acknowledged leaders and rules for sharing out loot. Justice, according to a standard definition, is giving each his due, so no social organisation can be just if it does not give God his due worship, and if it allows God’s servants to be removed from his service and enslaved by demons. There is true justice only in the res publica ruled by Christ, by which Augustine meant the city of God. Some medieval and early modern readers hoped that there could be an earthly res publica ruled by Christ if the state was subject to the spiritual guidance of the church, so that God would receive due worship from all, and rulers would govern with justice, acknowledging that their power comes only from God. But for Augustine that would not suffice, because the spiritual guides, the rulers and the subjects would not necessarily be citizens of God’s city. He recognised that self-love and desire for fame can make people behave with heroic virtue as individuals or as rulers, but he thought that it matters above all whether they love God or themselves; that decides whether they are truly blessed or truly wretched, and whether they will spend eternity in joy or torment.

Augustine did not think that we can achieve the city of God on earth, because of the fundamental problem of human nature. In his interpretation of the creation story in Genesis, God created humans as social beings, who were meant to cooperate in natural hierarchy: the stronger in body or mind would guide and protect the weaker, who would welcome their guidance. This, evidently, does not happen. God’s creation is good, but some angels at the moment of their creation, and the first human beings in the Garden of Eden, turned from God to do what they wanted, not what God wanted. It is impossible to explain why they did this, because their choice of a lesser good makes no sense. But the consequence, for humans, was a flaw in human nature. All humans inherit the wish to have their own way; this can be seen even in babies, who try to make parents and nurses follow their wishes. For one person to get their way, others must do as they wish, and since everyone wants their own way the result will be permanent conflict, at all levels of human society, unless there is social order. That means agreement on who gives the orders and who is authorised to enforce them if necessary: in Roman terms, who has imperium. The basic meaning of imperium is the acknowledged right to give orders; it came to mean the territory in which that right is acknowledged, the empire.

So there has to be imperium, because of human nature. There does not have to be empire. Romans liked to think that their wars were always just wars, and that they acquired an empire by fighting in defence of themselves or their allies. But even a just war depends on the injustice and aggression of someone else; glorious victories depend on killing people; and without justice, empires too are large-scale gangs, with a social contract and acknowledged leaders and rules for sharing out what they steal. Augustine argued against Romans who believed, in the words of Virgil’s Aeneid, that the gods had given them empire without limit of time or space, and a mission to rule, to ‘spare the conquered and fight down the proud’. History proved, Augustine said, that the gods gave neither physical protection nor moral guidance. The Roman Empire is one more example of the earthly city which loves itself and wants to dominate others, as Babylon had done. But among the rulers and administrators of this earthly city there are citizens of the city of God, and the city of God, intermixed in this life with the earthly city, benefits from some of its achievements. Rome was never a res publica according to Cicero’s definition but, Augustine reflected, another possible definition of a people is a gathering united by sharing with concord in the objects of its love; in modern paraphrase, a state aims to give people as much as possible of what they want. Those objects of love could be better or worse, but concord is worth having. Human peace, imposed and maintained by the power God has permitted to rule for a time, cannot compare with heavenly peace; common language, imposed by the imperial power, was achieved at a high cost in blood. But peace and communication are vital for human society. Augustine did not discuss further the best form of government and social organisation: obviously, it would be best if good people ruled and everyone followed Christian moral teaching, but bad rulers give moral training and remind us that power and success are not in themselves good.

Is City of God of more than historical interest? Augustine believed that Judaeo-Christian scripture is true and consistent, that everything depends on the hidden judgement of God, that for each of us there is an eternity of salvation or damnation. Augustine lived in an empire of cities, where the Roman state was responsible for peace, interpreted as defence against enemies and the maintenance of law and order; it was not responsible for universal welfare and fair distribution of resources. Much depended on the individual local governor, and though most emperors faced internal and external challenges to their rule, these were attempts to replace one monarch by another, not to replace monarchy by republican rule or direct democracy. There was no live debate on alternative modes of government. Augustine can be taken to encourage political quietism, even indifference, because of his overriding concern for relationship with God and for life after death. In this world, the citizens of the city of God are peregrini, ‘resident aliens’ away from their true home in heaven, who live here but do not quite belong. But that status does not mean opting out of the current social order: it means a commitment to the love of God and neighbour. Augustine insists that we must not be carried away by big words, by talk of kingdoms and provinces, glory and victory. We must remember the cost in blood, even of the peace and communication imposed by the Roman Empire; we must remember that power does not depend on merit and will not last. We must think in terms of individual human beings, not of nations and states and empires.

This essay originally appeared under the title Rome, Jerusalem and Babylon: Augustine on transient empires and everlasting cities in Nation, State and Empire: Perspectives from the Engelsberg Seminar, Axess, 2017.