With this vision of the darkness and tragedy of political life in place, Augustine, at last, turns back to his philosophical dispute with Cicero about the analytic nature of the commonwealth, the proper definition of what a commonwealth is. Recall that in Book 2 Augustine took up this issue of Cicero’s definition, of a city as an assembly united in fellowship by common agreement as to what is right and a community of interest, a city is a partnership of justice for Cicero here.

Here at last Augustine returns to this topic and argues that, since justice is a matter of giving each their due, a city that does not give God God’s due is not just, and thus not a city. Because God was never worshiped in pagan Rome, justice was never done there, and the city was never a true city, at least on Cicero’s definition.

This is partly one last smack at Rome, in its own self-regard. But it’s more primarily a critique of Cicero’s analytic political vocabulary and by extension the whole dominant political understanding of the ancient world. Justice, Augustine is saying, is first and foremost a form of worship. True justice is not defined by some grim vision of mere equity, a cold-hearted parceling out of finite goods to finite parties, after which each turns away from the others to feast on its own little grub in smug, solipsistic satisfaction.

Besides, if we all got what we truly deserved, there’s no way we would like it. For justice to be truly good news, it must flow from some source other than our sin-inflected perception of a finite world divvied up into lots like Jesus’s robes were divvied up at the foot of the cross. What is our due is what God has decided, gratuitously, to give us far beyond any merit we might conceive.

What, for Augustine, God has done to justice is like unto what God has done to cities. Every city, to be a true city, must be the city of God. Worldly cities can never be true cities—a real city must exceed the worldly city and reach for the divine. Cities may think, in orgies of self-congratulation, that they are systems of justice, righteous, noble nations; but no earthly city is actually that.

Far more psychologically accurate, if morally grubby, is Augustine’s proposal, cities are defined by what they love, by their common object of love. And yet, they aspire to so much more, justice and cities are to be founded on grounds fundamentally other than what we, in our fallenness, have imagined them to be. Cain’s city must become the New Jerusalem. But it cannot become that, from within history, for history is a record of continual crime and tragedy at best; so its healing must come from without.

Notes from Great Courses City of God by Charles Mathewes