Most people tend to have shape or form on their minds when they think of poetry. They expect to see relatively short lines of text, set well in from the left edge of the page, aligned on the left, though often with a regular pattern of indentations, and arranged in groups, like the stanzas of song lyrics. (They probably also expect to find rhyme and one of the four traditional rhythms, but I'd rather not worry about those things right now.).
It's true that most poems have been so formed. There seems to be something important about the visual impression of sentences broken up into lines, and the line breaks seem to affect the reader's eye in mysterious ways.
But form alone doesn't make poetry of words and sentences--though it can make verse. Arranging a work of philosophy or psychology or mathematics in the shape of a poem might make it verse, but won't make it poetry. Contrary to the popular perception, verse is neither necessary, nor sufficient for poetry. Other things are needed.
One of those other things is sound. Even a great poem on a page isn't poetry. You have to get it off the page and into the air to make it poetry. You have to say it to make it poetry.
But it has to be spoken RIGHT--or else it comes alive as a monster and destroys the village and eats the babies!
[the rest of the essay here: http://www.abstractconcreteworks.com/essays/PomSound/pomsound.html]