This is not a poem
Recently I was amazed to see a short piece published on Quartz (an article on Brexit of all things) refer to the famous “No man is an island” passage from Donne’s 1624 Devotions upon Emergent Occasions as one of Donne's most famous poems! Curious, I searched for the phrase and found — to my great dismay — it is identified as a poem on several widely-used websites. The text of the prose paragraph is given arbitrary line breaks to make it look like a free verse poem.
Poem hunter dot com presents it thus:
No man is an island,
Entire of itself,
Every man is a piece of the continent,
A part of the main.
If a clod be washed away by the sea,
Europe is the less.
As well as if a promontory were.
As well as if a manor of thy friend's
Or of thine own were:
Any man's death diminishes me,
Because I am involved in mankind,
And therefore never send to know for whom the bell tolls;
It tolls for thee.
It would be one thing to call this paragraph “poetic” — it certainly is. But it is not a poem, at least not in any sense that would have been recognized by Donne or his contemporaries. Vers libre was not invented until the nineteenth century. Inserting more frequent line breaks does not a poem make. Indeed, the line breaks are themselves irrelevant to the essence of poetry, which is primarily an oral-aural art, not a visual one. In other words, poetry (at least as it was universally understood before the last century) is easily recognizable as such without any help from line breaks or even without being seen, consisting in recurring patterns of sound. The poetic line is a rhythmic not a visual unit.
Poetry existed for millennia before the invention of writing. Writing and (later) print, opened up new possibilities for artistic cross-fertilization, of course; in the seventeenth century, for example, figured verse was quite popular. It adds a visual component by the arrangement of the lines on the printed page. Herbert’s “The Altar,” for example, or “Easter Wings” adds to the formal constraints of meter and rhyme a visual constraint, so that the lines, when written out, resemble (to some degree) the subject of the poem. This is a clever device, but does not challenge the fundamentally aural nature of poetry. When one reads “Easter Wings” out loud — as it is intended to be read — one hears the recurring rhythms and knows at once that what one is hearing is not prose. The clever way it is printed on the page adds something to the overall experience, but the success of the poem does not rest on this added visual dimension.
Perhaps you will say, “Poetry has evolved. It means something different now than it did then.” Fair enough. I might question how far the form can be transformed before one is really talking about a different category altogether. Nevertheless, if one is discussing a seventeenth-century work like Donne’s Devotions upon Emergent Occasions, do not mislead people about what it is.