What's the diffrence between poetry and delineated prose?

[Seraphim]

Perhaps you've been to a workshop, or a class, on poetry, and often the first question to be resolved is "What is poetry?"

OK, I've been to a few, and the answer concluded by the by the group has ranged from unsatisfactory to something worse. Generally their answer has fallen somewhere between  the lines of, "Whatever you choose to call 'poetry' is poetry," to "We can't explain it but we recognize it when we see it."  The "worst" seems to fall along the that poets are naturally (or unnaturally) blessed with the rare ability to know 'Truth' and are obligated to share it with the rest of the poor, pathetic mortals who haven't the gift.

Seriously. I've heard that one.

Regardless, I wonder if people are asking the the wrong question. When we read a poem, or hear it aloud in it's natural form, we are presented with a group of words, delineated into lines.  When we review them, how do we determine if the compilation of words is actually poetry, or if it's merely prose broken up into lines?

I mean, there has to be a difference, right? We have two different terms to describe the written word: prose, and poetry. If they were the same, there wouldn't be two different words, one assumes. We also have a 'prose poem', ostensibly. Poetry presented in paragraph form;  but the same question arises - how do we determine if one paragraph is prose, or whether it it is poetry incognito?

I suppose some might argue form equals function;  you can take a group of words, break them into lines and voila! - poetry.  But that's the part I find unsatisfactory.  There must be more. There must be a difference which is both evident and articulable.

So, what's YOUR answer to my question, "What is the difference between poetry and prose?"