Augustine's first move in describing the eternal state is negative: it is the complete absence of everything that mars present existence. No evil can enter it, no good is absent from it, no lassitude dulls activity, no want creates restlessness. This is not a passively blissful vacancy — it is a dynamic state of praise and knowledge, in which the whole person, body and soul, is turned toward God as a sunflower turns toward the sun.
The most difficult question Augustine addresses is what the beatific vision actually is — whether the saints will see God through bodily eyes or through the intellect alone. He refuses to be dogmatic. What he insists on is that the vision will be real and total: the saints will know God as they are known by God — not partially, through a glass darkly, as Paul says, but face to face. The resurrection body is not discarded or transcended in this vision; it participates in it, as every part of the person is ordered toward God.
The theological culmination of Book XXII — and of the whole twenty-two-book work — is the Pauline phrase "God will be all in all." Augustine takes this to mean that God will be the satisfaction of every desire: the life we crave, the health we seek, the nourishment, the glory, the peace. Not that creatures are dissolved into God, but that God becomes the inexhaustible object of every faculty, answering every hunger without ever being exhausted. To see this is to understand why the City of God ends not with an argument but with a doxology: the whole work has been pointing toward a state that can only be praised, not described.
Augustine's account of eternal life is not an escape from the questions he has raised throughout the work. It is their resolution. The two cities are separated; the restless heart finds its rest; the order of peace is finally and perfectly achieved; providence has accomplished what it set out to do. The city of God is at last fully itself — not as an idea or a hope, but as an eternal reality.
The beatific vision is treated in Book XXII, chapters 29–30. Augustine's discussion was the primary source for the medieval theological tradition on the beatific vision, including Aquinas's treatment in the Summa Theologiae.