Some people dislike poems that don’t rhyme for much the same reasons that they dislike hoodies with studs in their noses. Both seem to pose a vague threat to social order. Rhyme in poetry, like metre and rhythm, reflects a sense of balance and symmetry; to banish it, as a lot of modern poetry does, may seem like opening the floodgates to anarchy. Start off with free verse and you end up with free love.

Consider this couplet from the 18th-century poet Alexander Pope:

True wit is Nature to advantage dress’d:

What oft was thought but ne’er so well expressed.

Forget what the verse says for a moment, and look at how it says it. The combination of that clinching rhyme with two perfectly regular iambic pentameters creates a sense of harmony and concision. The lines are without an ounce of superfluous flesh: elegant and economical, easy and sophisticated. In fact, they are almost a form of wit in themselves. They are an example of what they are talking about. It is no surprise, then, that Pope was a traditional-minded Tory who believed in a well-ordered world. It is as though the couplet gives us a microcosm of such a reality.

Contrast it with these lines from Wilfred Owen, who fought and died in the First World War:

Happy are men who yet before they are killed

Can let their veins run cold.

Does this rhyme? Yes and no. “killed” and “cold” are what is technically known as a para-rhyme — a not-quite rhyme. Owen uses such verbal near-misses to magnificent effect (brothers/ withers, fleers/flowers, groined/ moaned), to create an eerie effect of dissonance. These almost-rhymes suggest a memory of order and harmony that is now growing dim and unstable. Things are struggling to hold together. That wasn’t an unusual feeling in the middle of a war that seemed to mark the end of civilisation.

Rhyming involves a combination of sameness and difference. We hear “dragon” and “wagon” as akin, but also as dissimilar. This yields the rather infantile delight that human beings always seem to take in doublings and mirrorings. There is something seductive about things that are both like us and not like us, both intimate and strange. Think of men and women. Myth and fable are full of such unexpected affinities. There is something magical about rhyming.

Sameness in itself is boring. A constantly repeated word or image starts to stale. Difference in itself is disorientating: a poem without any kind of regular pattern would sound pretty much like a pub conversation. Blend the two together, however, and you have an experience too varied to be monotonous, and too familiar to be threatening.

The same goes for metre. If we look back at the lines from Pope, we can see that they, too, combine sameness and variety. As we read them, we can hear in the background, almost unconsciously, the regular thudding of the iambic pentameter: di-dum-di-dum-di-dum-di-dum-di-dum.

Yet if this was all we could hear, the lines would be as tediously predictable as a nursery rhyme. Once we give voice to the lines, something different happens. The speaking voice has its own idiosyncratic lilts and stresses, that add variety to the regular plodding of the metre. You could read these lines aloud in lots of different ways. So the iambic pentameter — the most typical metre in English verse — weaves together freedom and order, flexibility and regularity, the distinctive tones of an individual with an impersonal structure. This, among other things, is an idealised view of what is peculiar about English civilisation.

T. S. Eliot once declared that there was no such thing as free verse. Some poems, it is true, don't rhyme and are not written in metre. Yet this does not necessarily make for a kind of linguistic laissez-faire. Poems like this can still have structure and pattern, but of a more discreet kind. Think, for example, of some of Eliot’s own most celebrated lines, the opening of The Love Song of J. Alfred Prufrock, which mark the precise moment when poetic modernism arrives in Britain:

Let us go then, you and I,

When the evening is spread out against the sky

Like a patient etherised upon a table.

Somewhere behind these stumbling, lurching lines, one can still hear the faint ticking of an iambic pentameter. But it is a metre that has gone grotesquely awry. It has turned into a parody of itself. Modern experience seems to lack pattern and coherence, and poetry, if it is to be authentic, must reflect this.

Rhyme, then, is not essential to poetry. Those who remain unpersuaded should open any page of Shakespeare.

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