There are, by my count, only two things that can save a long poem in English.
- Heterogeneity (Eliot and Pound; and those polyphonic, formally quite various sustained dramatic poems of Shakespeare) and/or
- Rhyme (Chaucer, Golding’s Ovid, Chapman’s Homer, Marlowe’s Hero and Leander [a very underrated poem, check it out], Spenser, Pope’s Homer, and 19th-century narrative poets like Byron and Sir Walter Scott).
Now, you may object that Paradise Lost is in blank verse but not rhyme, and not particularly heterogenous in tone or form. I would say that there is a reason Milton is often hard going for a modern reader: True Religion aside, he’s hell-bent on applying principles of ancient Mediterranean (“Classical”) cultures to post-medieval English verse. Most people see that clearly enough in his overdoing the Latinate vocabulary and his grudging compromise with the fact that you can’t construct an English sentence with the words in any order you please the way you can with Latin. But it also shows up in his opting out of rhyme, which he calls a “troublesome and modern bondage” (italics mine). By “modern” he doesn’t mean, as we do, about seventy years ago; he means Ancients versus Moderns, as in, Homer and Virgil didn’t rhyme, so I won’t rhyme, either. Milton, however, dislocated so many aspects of English to fit the patterns of the past that things actually ended up working, in their own knotty way; the language had been sufficiently weirded.
Note that Pope, whose sense of the requirements of English was keener, doesn’t opt for unrhymed verse even when he’s translating an unrhymed Classical poet. Milton’s example, still historically recent, fails to throw off his formidable instincts as a versifier. (In our own day, the poet-classicist A. E. Stallings’s translation of De Rerum Natura is saved—from, well, Lucretius—by the use of a rhymed fourteener.) To see how unreadable classical poetry can get when translated into Miltonics (a subspecies of blank verse adapted to reproduce the behaviors of classical verse in English), consult Charles Eliot Norton’s Virgil.
Milton’s example convinced later poets that such a poem was desireable, or even possible, coming from anyone other than Milton. The insufferably long homogenous unrhymed poem, from Edward Young’s Night Thoughts to Robert Bridges’s The Testament of Beauty, is to be blamed on Milton, who (alas) perpetrated it successfully. Much later, we get Wordsworth’s The Excursion and Tennyson’s Idylls of the King, where “major” poets go for long-form, homogenous blank verse—philosophical in one case, narrative in the other—and don’t quite hook the future. Chaucer, Pope’s Homer, Byron’s Don Juan, and Whitman’s “Song of Myself” all have stayed rather readable. Wordsworth and Tennyson live on, as they should, primarily through their shorter lyrics. There are probably readers out there who consider their long ones “successful,” and if you did your thesis on The Prelude, you will find this dismissal atrociously ignorant.
A comment about proseyness is necessary here. There is a reason long poems happen in the fragmentary forms and “lyric sequences” now. It’s the Goldilocks Effect. Too much density of language over too many pages gets exhausting for a reader. The mind waits for Homer to nod. Yet what our poetic culture thinks of as “good” or “true” poetry is nearly synonymous with lyric “intensity” of emotion or language, which necessitates a great amount of information per line. If you can consider these things in terms of the motion of the eye and intellect, the lyric tends toward stasis. But a good narrative, like a good argument, is kinetic; the quicker it rips along, the better. This spells trouble for narrative and philosophical long-form poems.
No wonder Alexander Pope writes such good didactic and philosophical poetry: It’s his clarity of language and his use of the heroic couplet. The clarity requires very little dwell time; the swift and repeated payoff of rhyme helps you down two lines for the effort of one. Two lines travel as a unit, and they travel light and fast. Enjambement has a curiously slowing effect in Pope, rare as it is; you feel slowed down to the speed of prose, which people mistake as the quickest reading there is. (There is one form of writing in English that is faster-paced than prose: the verse of Pope. His poetry speeds past on kangaroo-hop couplets.)
So either the language is too dense, and the attention gives out after a few pages. The more diffuse the language gets, though, the more the pages fly by, the more one wonders why the poet doesn’t dispense with line breaks altogether and just run all this together. Goldilocks complains: This is too dense, but that is too diffuse. In the 21st century, Goldilocks has increasingly found prose “just right” when it comes to long form narrative or didactic/philosophical reading.
The only things that prevent the Goldilocks Effect, in practice, are either a willful ellipsis/disjunction/fragmentation, or a parceling-out of the long poem into sequential semi-free-standing shorter poems that mimic the books of poems we are used to. A straightforward metrical scheme like blank verse won’t do it if there isn’t some Weirding Principle simultaneously at work, like Milton’s Latin obsession. A third and in modern world least utilized (least utilized, because most difficult) possibility is the rhyme scheme. Down this decades-untrammeled path there may yet lie poetry’s most fruitful direction for expansion, and the eventual reconquest of the long form.