In the popular consciousness rhyme and poetry are bound together. “I’m a poet / And I don’t know it.” No matter that English poetry managed without rhyme for centuries, that Milton argued against it in the preface to Paradise Lost, or that our best-know poet wrote most of his lines in blank verse: proper poetry rhymes, and it’s only new-fangled modern stuff that fails to.

The argument is so well-worn (and pointless) that it’s easy to overlook the more interesting question of what rhyme actually is. We know that “The cat / sat / on the mat” rhymes; that “O pardon me, thou bleeding piece of earth / That I am meek and gentle with these butchers” doesn’t; and that “They gave us six fishhooks / and two blankets embroidered with smallpox” sort-of does.

But the closer you look, the less distinct things become. Rhyme isn’t a binary thing but a question of degree. In the spoken music of poetry there is a near-infinite range of effects caused by how like or unlike different words sound.

A word’s purest rhyme is with itself. When every consonant, vowel and phoneme is the same, the likeness is so absolute that it’s often considered cheating. Nonetheless, rhyming a word with itself can have a powerful effect (albeit one to be used sparingly), as in James Merrill’s “For Proust”:

Over and over something would remain
Unbalanced in the painful sum of things.
Past midnight you arose, rang for your things.
You had to go into the world again.

Only slightly less pure than self-rhyme is rhyming with a homophone. Later in the same Merrill poem we find:

She treats you to a look you cherished, light,
Bold: “Mon ami, how did we get along
At all, those years?” But in her hair a long
White lock has made its truce with appetite.

The risk with such close rhymes is that they can easily become monotonous (Merrill’s don’t, but he has to work very hard throughout the poem to offset them with other, more varied sound patterns). Our ear wants variety as well as pattern. One of the oldest solutions to this is the configuration we all recognize as full rhyme, where two words have different beginnings but share the same end-sound:

What dire offence from am’rous causes springs,
What mighty contests rise from trivial things,
I sing – This verse to Caryl, Muse! is due:
This, ev’n Belinda may vouchsafe to view:
Slight is the subject, but not so the praise,
If She inspire, and He approve my lays.

This would be impossible to sustain for six lines – let alone the eight hundred that make up The Rape of the Lock – if each word rhymed with itself. Instead we have both similarity and difference at the end of each line; both pattern and variety. But even so, heroic couplets like this can quickly become tedious or sing-songy. There’s something a little bit too predictable, a little bit too samey about the matching pairs.

Poets have different ways of countering this. Rhyme words can be separated by more than one line, giving more intricate patterns that delay resolution and keep more than one rhyme-sound in play. Compare the six lines from Pope above with the following six from Arthur Symons:

Also I have this garret which I rent,
This bed of straw, and this that was a chair,
This worn-out body like a tattered tent,
This crust, of which the rats have eaten part,
This pipe of opium; rage, remorse, despair;
This soul at pawn and this delirious heart.

The longer the distance between two rhyme words, the more complex the effect and the more subtle the resolution of the sound-pattern. Our ears can detect and delight in rhymes that our conscious minds don’t always spot (although there are limits to how far apart two words can rhyme and still be noticed – see Dylan Thomas’s “Prologue” to his Collected Poems for a fascinating failed experiment).

Just as moving rhyme words further apart can lessen the monotony of too many consecutive couplets, so can reducing the strength of the rhyme. In full rhyme both the vowel sound and the closing consonants are the same, but poets can choose to repeat only the closing consonants (half-rhyme) or only the vowels (assonance, which is essentially rhyme without the consonants). Listen to the difference between these couplets from Wilfred Owen and the previous couplets from Pope:

Then, when much blood had clogged their chariot-wheels
I would go up and wash them from sweet wells,
Even with truths that lie too deep for taint.
I would have poured my spirit without stint
But not through wounds; not on the cess of war.
Foreheads of men have bled where no wounds were.
I am the enemy you killed, my friend.
I knew you in this dark; for so you frowned
Yesterday through me as you jabbed and killed.
I parried; but my hands were loath and cold.
Let us sleep now…

In reality there aren’t just “full rhymes” and “half rhymes” but endless gradations of similarity and difference. The likeness of “war” and “were” is closer than the likeness of “killed” and “cold”. Part of the beauty of a well-written poem is the way it plays with dissonance and harmony, now bringing sounds closer together, now pushing them further apart. This is true within lines as well as at their ends (“The sunlight on the garden / Hardens and grows cold”) and ultimately applies to unrhymed poems as much as to rhymed (“Of man’s first disobedience and the fruit / Of that accursed tree whose mortal taste”). It’s the very substance of the music.

A poet like Paul Muldoon can stretch rhyme to breaking point (rhyming “English” with “language”; “graven” with “paper”), just as a poet like Byron can rhyme so many consecutive syllables that the resolution becomes delightfully ridiculous (“But oh ye lords of ladies intellectual, / Inform us truly – have they not henpecked you all?”). A sonnet that rhymes ABAB CDCD EFEF GG will have a very different effect on our ears than one that rhymes ABBA CDDC EFG EFG, even if the rhyme-words and subject matter are the same. Instead of tired arguments about whether or not poems should rhyme, let’s spend some time thinking about how they rhyme (even the ones that don’t).

Here’s a rhyming poem (that doesn’t show ’em):

from The Tempest (William Shakespeare, 1610)

You do look, my son, in a moved sort,
As if you were dismay’d: be cheerful, sir.
Our revels now are ended. These our actors,
As I foretold you, were all spirits and
Are melted into air, into thin air:
And, like the baseless fabric of this vision,
The cloud-capp’d towers, the gorgeous palaces,
The solemn temples, the great globe itself,
Ye all which it inherit, shall dissolve
And, like this insubstantial pageant faded,
Leave not a rack behind. We are such stuff
As dreams are made on, and our little life
Is rounded with a sleep.