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Nonetheless, there will be a lot of ways to read something. Even a single line can be read in multiple ways — give it to an actor, watch him go crazy with it. As for "the well read can access such information almost immediately"? There are people here who (as far as I can tell) are well read and who don't know what metre is.
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If I remove the line breaks from a poem, does it stop being a poem? If I fill my prose story with alliterations, and internal rhymes, and break lines to make it look like verse, does it begin being a poem?
While I like both Three Tanka for Yosano Akiko and The Coin, I feel that the first is much closer to being prose, despite what you've said, about there being "studied technique" in it. Three Tanka is much more about the imagery it conjures than about a connection between writer and reader. The coin, on the other hand, presents a framework which requires some deeper engagement from the reader, giving only this hint: "We who live our lives within the outer margin, with sad Humanity we face our equivocal fate." You could "read it in 30 seconds, and feel like it says something", but then you'd be missing on actually connecting to its meaning.
I've read and written music since I was a kid. There are many factors that aren't included in typical notation that the musician has to interpret and inject their own creativity. It's more precise an art than interpreting Wallace Stevens, but perhaps almost as precise as a number of English language poets of the Romantic period:
Chameleons feed on light and air:
Poets' food is love and fame:
If in this wide world of care
Poets could but find the same
With as little toil as they,
Would they ever change their hue
As the light chameleons do,
Suiting it to every ray
Twenty times a day?
If you read this twice through and spoke it as you believe the author intended and 10 other poets did the same how different would each interpretation sound?
Line breaks aren't what make poems poems. ClearDayNow's poem without enjambment changes nothing:
We who live our lives within the outer margin,
with sad Humanity we face our equivocal fate.
For living is seeing a double sided coin
Spin eternally, never knowing the image that Is repeated there.
We hang suspended in our Unbelief, ever hoping, never knowing.
Protecting the hurt by saying we believe In disbelief.
Ever reeling, ever dealing, never seeing We are the thing we seek.
The internal, gerund heavy rhymes are still present. There might be a half-rhyme or two, the alliteration; it qualifies on both borders of poetry and prose. There never has been a line in the sand, while there certainly are poems that aren't prose and prose that isn't poetry. Which would be the point of protecting poetic traditions in the face of the movement toward making poetry closely resemble prose so much that it might not be worth considering it as poetry or possibly forgetting poetry altogether and let it be a dead art.
Anyway, no one's saying this couldn't be a poem and also prose. That wasn't my main criticism of The Coin, by the way, the point was that there's nothing to connect with in the poem during my thirty second read and re-read. My main criticism of Three Tanaka would be that while it fits within criteria for Tanaka, it says very little about the author as poet. It's like judging Ernest Hemingway as author based on the six words attributed to him about baby shoes for sale. There are forms such as Tanaka, Haiku, Triolet where a poet can exercise within the limited parameters quite well, OpenField is fairly successful.