Augustine’s immense work, The City of God, responded to pagan criticisms of Christianity after the sack of Rome in 410 A.D. The book modeled Christian philosophy in the late classical world, and Augustine synthesized history, apologetics, philosophy, and theology as he wrestled with defenders of traditional Roman religion and classical philosophy. Read politically, The City of God contains two essential teachings: first, a Christian philosophy of history, and second, a biblical teaching on anthropology, ethics, and politics, so that those who belong to the City of God might know how to live among the City of Man.
Most significantly, Augustine articulated a Christian philosophy of history. The reigning ideology in imperial Rome asserted that Rome would exist forever and would civilize the world. The repeated invasions of the Goths and their three-day sack of Rome proved a shock to that ideology. In the aftermath, Augustine supplied a new philosophy that interpreted the ways of God to man. His was a biblical interpretation of secular events. The kingdoms of men may wax and wane in time, but God had planned an ultimate destiny for all mankind from before all time. Now Rome ruled most of the known world, yet its foundations were fracturing, not firm. This new reality, said Augustine, should surprise no one. It was in fact an old story of rise and decline, for the City of Man was separated from God and therefore unstable.
The City of God, however, was everlasting. It was the only eternal city, in which God’s people would find their true rest. God had created the world, angels, men, and animals with a purpose, knowing full well that sin would enter the world. Some angels (the demons) fell away from the blessedness of God by choosing to imagine themselves equals with God, and they introduced humans to the same ideas and same separation from God. God, however, began building the city of God by drawing men to Himself by their faith, as recorded in the Old and New Testaments. The members of this city would find everlasting blessedness in God at the final judgment – this was their hope of peace and happiness. In other words, God’s history had definite direction and an endpoint.
A well-ordered soul loves God as he ought, and therefore loves himself as he ought, and therefore loves his neighbor as himself.
Augustine’s philosophy of history demanded an explanation of human anthropology and ethics. The sin of Adam, father of all mankind, brought sin and disorder to the human body and soul. Instead of cleaving to God, man now separated himself from God. The soul no longer ruled properly over the body, and passions dominated while right reason was subdued. Vanity, lust, and all forms of sin marked every aspect of human life. In this situation, there was no peace.
And peace was the key. Augustine argued that peace – broadly understood as the harmony of all the parts of a community or relationship – was the end at which all subordinate ends aim. A well-ordered soul loves God as he ought, and therefore loves himself as he ought, and therefore loves his neighbor as himself. He explained that “Peace between man and God is the well-ordered obedience of faith to eternal law. Peace between man and man is well-ordered concord” (19.13). In loving and worshipping God the creator, man would again find his peace and eternal blessedness.
The Augustinian anthropology of sin contained an ethical implication. Members of the City of God have a duty to love God, for this alone restores peace and order to their beings. From this, said Augustine, “it follows that he must endeavor to get his neighbor to love God, since he is ordered to love his neighbor as himself” (19.14).
Socially, this means that Christians have a duty to teach God’s truth and discourage sin. This truth had larger political significance. Augustine explained that “To be innocent, we must not only do harm to no man, but also restrain him from sin or punish his sin, so that either the man himself who is punished may profit by his experience, or others be warned by his example.” (19.16) Augustine did not say whether or how far the civil magistrates should be involved in promoting the true faith (the language of punishment and warning others by example suggests that civil magistrates should be involved), but as pertains to the relationship between man and man, he affirmed the duty to encourage righteous behavior and forcefully to discourage wickedness in human affairs.
Augustine never expected a perfect earthly society. Even the regenerated Christians who belonged to the City of God were still marred by the fallenness of sin. But they could live among the City of Man and appreciate God’s grace to their unbelieving neighbors.
“To be innocent, we must not only do harm to no man, but also restrain him from sin or punish his sin, so that either the man himself who is punished may profit by his experience, or others be warned by his example.” Augustine
Indeed, Augustine’s philosophy of history recognized that earthly society was mixed. How should the city of God conduct itself toward the city of Man? They shared some goods in common, the most important of which was temporal peace. Augustine repeatedly employed the language of pilgrimage: “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” (19.17). Material life was held in common; spiritual life was distinct. The saints of God should seek the health and peace of the City of Man, for (and here Augustine quoted Jeremiah 29:7) in its peace they would find peace. He observed that, “Miserable, therefore, is the people which is alienated from God. Yet even this people has a peace of its own which is not to be lightly esteemed. . . . [F]or as long as the two cities are commingled, we also enjoy the peace of Babylon” (19.26). In the protective peace of Babylon, members of the City of God could endeavor to teach their neighbor the true means of ordering their soul: loving God.