Much hate has been loosed on the literary heritage of Aurelius Prudentius Clemens (b. AD 348), a Spanish-Roman public servant who spent his later years writing verses in celebration of the rise of Christianity in the Empire. His use of allegory in the Psychomachia harkens back to the pagan Statius’s epic poem The Thebaid, but develops the genre for explicating Christian moral doctrine and the inner conflict caused by concupiscence in the soul. Modern literary critics prefer the subtlety of the novel to the so-called crassness of the allegory, but for many centuries Allegory was a popular poetic genre in Europe, as was its child-genre Romance (what we would today call adventure stories).
Prudentius, though, was not simply an allegorist. He was, as H.J. Thomson has written, “a pioneer in the creation of a Christian literature, and has the credit of originating new types of Christian poetry, the literary hymn, the moral allegory, and what has been called the Christian ballad” (from his introduction in the Loeb Classical Library). Many of his poems were adapted for use in the Roman Breviary and made their way into popular hymns. He merged classical sensibilities with Christian orthodoxy and orthopraxis, and defended doctrine against rising heretics with the respected verse forms of the day.
The importance of a Catholic using the best literary tools of the pagans against them in a time when the Church’s social position was growing but precarious should not be undervalued. Louis Snyder, SJ wrote of Prudentius’s importance in his commentary on the Psychomachia:
Grant that Prudentius is artificial in the handling of his theme, grant that false ornament is not foreign to his descriptions and that one grows weary over his prolix speeches and winces, perhaps, at his occasional play on words or likes not his alliteration, assonance, or patent imitation of Virgil; still one must admit that all these means of presenting a subject were familiar to, even expected by, the educated Christian reader of the fourth century. These Christians were interested to hear Prudentius sing their doctrine in a cultivated strain, using all the artifices of the schools. We who have a Dante, a Milton, a Spenser, and a host of lyricists who long since have wedded literary forms to the thought of Christianity, sometimes fail to see and grasp the situation of an age when imaginative Christian letters were unknown. We fail to recognize what it meant to those cultured Catholics to have one of their own, one with all the zeal and fervor of an apostle, imparting to the classical molds of literature the fresh outlook of Christianity. (12)
Indeed, the allegory in his Psychomachia is occasionally eye-rollingly simple. He pits feminine personifications of virtues and vices against one another on the battlefield—Faith against Pagan Worship, Humility against Pride, Chastity against Sodomy, and so forth—and has them fight in a carnal manner. However, his cleverness is in showing that this is not a mere physical conflict, and that the virtues cannot always win their battles by sheer brutality. For example, Patience defeats Wrath not by fighting but by donning impenetrable armor, and waiting for Wrath to murder herself after her attacks are all frustrated. This may not make for great drama, but it is good spiritual advice, and that is the main point. The poem ends with the vices all slain, and a Temple erected in the soul with a throne for Holy Wisdom to sit upon.
The use of Allegory diminished greatly with the Renaissance, perhaps surviving longer in painting than literature. The tools of the genre were gradually sublimated into an obscurely subtle use of symbolism in the modern novel. The postmodern novel casts a skeptical eye even on this hidden layer of meaning. C.S. Lewis, no particular fan of the Psychomachia itself, nonetheless offered a defense of the genre in his study The Allegory of Love:
We cannot speak, perhaps we can hardly think, of an ‘inner conflict’ without a metaphor; and every metaphor is an allegory in little. And as the conflict becomes more and more important, it is inevitable that these metaphors should expand and coalesce, and finally turn into the fully-fledged allegorical poem. It would be a misunderstanding to suggest that there is another and better way of representing that inner world, and that we have found it in the novel and the drama. The gaze turned inward with a moral purpose does not discover character. No man is a ‘character’ to himself, and least of all while he thinks of good and evil. Character is what he has to produce; within he finds only the raw material, the passions and emotions which contend for mastery. That unitary ‘soul’ or ‘personality’ which interests the novelist is for him merely the arena in which the combatants meet: it is to the combatants—those ‘accidents occurring in a substance’—that he must attend. (60-61)
I have suggested in an earlier post (“Are We Wrong About Catholic Literature?”) that it would be worthwhile to do some archeological work and try to reconstruct what, if any, older Catholic literary traditions there might be. Prudentius’s legacy remains at the forefront of our literary patrimony, whether we appreciate him today or not. In a sense, he was doing what the best Catholic novelists of the last few centuries have done: appropriating the artistic movements of the time for their own use. But there is still a wide gulf aesthetically between Allegory with its densely symbolic poetics, and what we today rather simplistically call Fiction.
At the very least, I would suggest that an appreciation of allegorical methods as worked out in older Catholic literature could be positively fruitful as we write our own stories, today. They need not be slavishly imitated—although I would love to see the results of such imitation from a sure hand—but I think they should not be booed off the stage merely because tastes have been altered. They may yet be altered again.

Patience is ready when you are.
This makes me think of “Animal Farm” – it’s probably the most successful allegory of the 20th Century and, even though we all know the story that inspired it, the way he approached the characters and his angle as ‘fable’ did a lot to avoid the eye-rolling pitfalls most allegories fall into.
Yann Martel’s “Life of Pi” and “Beatrice and Virgil” are two recent attempts at making allegory culturally relevant again and, even if the books themselves aren’t the best (especially “B and V”) they’re interesting just for how he tries to reconcile the form to an age that demands more psychological depth to their characters and plots.
Spoilers ahead:
“Pi” basically throws the gauntlet at readers and asks them to sort through whether or not everything that happened on the boat was allegory or *literally* happened, and even if his religious literacy spreads rather thin (the unspoken question is whether or not we are comforted by attributing things to God’s providence or not) it’s a fascinating postmodern spin on the genre. “B and V” plays further by having the titular story (of Beatrice, a donkey, and Virgil, a monkey, both representing Holocaust victims) being a story-within-a-story where their writer’s the main character and he himself grapples with using allegory to deal with brutal realities. I wouldn’t be the first to say their literary pleasures are top-notch, but they’re unavoidable when we think about how allegory continues to evolve as a form.
I get the sense sometimes that allegory’s migrated more to oral formats, especially homilies. Like you said earlier, the Psychomachia wasn’t made to be an edge-of-your-seat thriller so much as a vehicle for moral advice, and anecdotes that priests tell during the liturgy follow the same trail. If we watch enough TED talks we’ll see the same thing: short allegories told to help give people a better sense of an idea. While we might wonder why allegory disappeared, it might be better to say the form just jumped to another ship and is continuing to enjoy lasting value.