I have thought about this a long time. I have thought about it since the time that Gerard Manley Hopkins convinced me that Catholicism was the way to go. I don't recall precisely how it happened. What I remember is reading Hopkins in a Seminar on Victorian Poetry (taught by one of my most enthusiastic professors). Somehow a discussion evolved, or I read in an introduction to Hopkins that he believed in something called "The Real Presence." Now, I had slim to no notion of what this was, but the notion attracted me, and if the idea gave rise to the glorious poetry I was reading, then perhaps there was some validity to it, perhaps it warranted further investigation. Thus, through the work of Hopkins, and C.S. Lewis, I found my way back to the church of my youth (Southern Baptist), and from there to the Catholic Church.
Dubay makes a powerful argument in favor of beauty as evidence of God in the universe (The Evidential Power of Beauty) and the Holy Father is convinced that Artists, and by that I am certain that he means Artists in the broadest sense of the word, have a great deal to contribute both to the support of the faithful and to the evangelization of the unbeliever.
What then must be the essential ingredients of any work that might help people come to God. First and foremost, I would think, integrity--a grass-roots, at-the-bottom, fundamental commitment to telling the truth as you see it, even if that truth seems to run counter to God. For example, though Wallace Stevens spent much of his life as a professed Atheist, I think much of his poetry deals with the question of the existence of God, and by stating his case honestly, one sees hidden within the poetry the opposite case as well. Some have argued that "Sunday Morning" is the great atheistic paean. And yet the poetry is, as one would say, "Christ-Haunted." One gets the impression that "methinks the artist dost protest too much." That he struggles mightily to make his point only to fall back on ambiguity and uncertainty that ring with a certain theistic tone. The "Disillusionment at 10 O'Clock" appears to be about aesthetics (another obsession of Stevens's) but it can be read to being about the drabness of the world without the Divine Imagination. So truth will out if one is as honest as he or she could possibly be.
The second quality is accessibility. Geoffrey Hill may convert a PoMo, but the man on the street will take one look and answer with "Say what?" T.S. Eliot, in "Ash Wednesday", "Preludes", and "Prufrock" gives us a certain kind of accessibility and encouragement. Hopkins too, though he is quite difficult. Accessibility means the invitation to dine, not spoon-feeding. There must be something at the surface of the poem that is fundamentally attractive and which encourages the prospective convert to read the work. But the surface must not exhaust the purpose of the poem. It can't be a sing-songy rhyme that tells about how lovely are the daffodils and tulips scattered by the saint around the feet of God. A poem like that can work, but most often it becomes a Helen Steiner Rice catalog item.
The third quality is that the work must be literature. It must be much better written than the vast majority of the novels that are being issued from the Catholic Novel Mill. I take a glance and see that the work of Bud McFarlane has actually been given at least one and perhaps two awards for Catholic Writing and I am appalled. Perhaps if the award was for piety in print I would have less objection, but McFarlane's work needs work. The sentences are as sloppy as most of what I publish on this blog. When writing a blog, a certain amount of that is allowable, but when executing a novel it is an unforgivable sin. Catholic and Christian work needs to be judged by the same standards that are applied when one looks at any work of literature. If the work does not rise to that standard, it should be neither awarded nor exalted. There is no reason that a Catholic Writer cannot consistently produce the work of say a Ron Hansen or a Jon Hassler (at a minimum) or a Flannery O'Connor, Shusaku Endo, Graham Greene, or best of all an Evelyn Waugh. We no longer truly encourage writers of this sort. We award our awards to those who can be most "Catholic" or most overtly religious--not a good way to decide any artistic merit.
This is a start at thinking about what might go into poetry as evangelism. And in this impulse, it might be possible to reignite the epic impulse that too long has lain dead. Chesterton did write both "Lepanto" and "Ballad of the White Horse." I am not particularly fond of these as poetry--a trifle overcontrolled and stuffy (Chesterton's best work is by no means his poetry. On the other hand, Belloc had some truly wonderful light verse and some really fine poetry as well.) The Epic impulse requires a single eye, an unfragmented vision. And the only way that is available in the modern world is through a denial of the modernist/postmodernist influence through a solid base in the truth of Christianity.