This book aims at joy--nothing else. Joy is intensified in the despair of (post)modern life. Leithart also neatly connects joy (think comedy) with the Trinity. Leithart aims to show eschatological moments within the Trinity. And if these moments take place within space-time, then this book also aims at eschatology. An eschatology of hope.
The short thesis of this book is that Western literature moves from Tragedy to Comedy and from Comedy to Deep Comedy.
Beginning with Tragedy:
The pivotal work of ancient history is Homer. The Iliad--here Leithat defies convential terms--is a tragedy. Good people (well, protagonists anyway) gone bad. It is hard to find a happy ending to this story. More importantly, such a framework tending toward despair is inherent in a pagan (greek) culture.
Western literature, then, while still pagan, tries to move towards Comedy. Of course, the Odessy has a happier ending than the Iliad. But it lacks the deep resorvoirs of the Christian story. Odesseus knows he will die. And having been to Tarturas, he knows it is better to remain alive.
But The Aeneid is happier, right? Well, kind of. Aeneus does build a mighty house, but only by toppling other houses. Aeneas brings the destruction of Troy with him to Carthage. Aeneas, despite great moments, turns Carthage, represented by the suicidal funeral pyres of Dido, into another Troy.
But something happens with the Western Story. Christ in a way takes the Platonic worldview and subverts it. This is Leithart's most brilliant moment in any of his books. He wrestles with the challenge given by postmodern philosopher Derrida: All literature (or story) must have a supplement to the Origin. But the supplement is almost always a degeneration of the Origin. This shows up in literature. The sons (Zeus and the gods) overthrow the fathers (Chronus and the Titans). Supplementation for Derrida--and the greeks--is violent.
Interestingly, there is no such thing as "origin" unless there is also a moment of "supplementation." Accordling (and contra to Plato), there is no such thing as pure origin, pure essence, or a pure stream. It is already supplemented. At this point Derrida, himself an unbeliever, comes very close to a dark Trinitarianism. He, like Athanasius, sees that there can be no Father without a Son. But Derrida prefers Hesiod (violence) to the Gospel of Jon (perichoreisis).
This is the eschatological moment in the Trinity, and in Western History. Unlike all of history before it, this time the Son does not violence the Father. Christ reveals the Father. Does the Father's will. Incarnates the Father's love.
Here is a Trinitarian argument for you: There can be no Father without the Son. But he has also been the Father for all eternity. Therefore, there must have been a Son for all eternity.
The newly revealed (although ancient) Trinitarian theolgoy was a joyful theology. The Christian gospel--the Christian story--moves from "glory to glory" (1 Cor. 3). The end is always better than the beginning. The medieval romances, despite some lapses, are much happier than Homer. The Christian (medieval) world is thus supernaturalized. The Christian hero is thus an adventurer.
This book may well be Leithart's best work. The chapter "Supplement at the Origin" may well be the best thing on trinitarian theology I have read. It is hard to say how much I recommend this work.