Augustine uses the idea of the city as a symbol representing each of the contrasting communities that he sees in the arc of human history. On one side, there is the “city of God,” made up of all those people who are being redeemed by God’s salvation and whose destiny lies in an eternity of joy in God’s presence. On the other side, there is the “earthly city,” made up of those people throughout history who choose their own way rather than God’s, for which Augustine uses Rome as his leading historical example. Since the earthly city rejects the goodness, truth, and beauty of God, its highest fulfillment lies not in the eternal state but in the temporal realities of earthly existence.

Both of these cities exist together in this world, and while the earthly city sometimes manifests itself in nations and empires, the city of God does not. Its members live alongside those of the earthly city, but their true citizenship belongs elsewhere, even as they respect and follow the laws of their local societies. Augustine hopes to encourage his readers that even if their temporal political state might be failing, their ultimate hope (if they are Christians) lies in their citizenship in the city of God.