I did not intend to be "provocative" when I said that the paragraph is the smallest unit of scholarly composition. Though it's increasingly unfashionable (for good reason), I could cite Strunk and White's Elements of Style for support. Instead, however, I'm going to take up the challenge and show what I mean by comparing the poetry and prose of my favorite poet, Tony Tost.
Consider this paragraph (you can read it in context at The Rumpus), taken from his book Johnny Cash's American Recordings (Continuum, 2011):
If Cash’s violence was often excessive, it was never gratuitous. “Blessed with a profound imagination,” Dylan wrote of Cash, “he used the gift to express all the various lost causes of the human soul.” Cash took residence within songs in which sinners too were brought into conversation with the possibilities of grace and human dignity, songs in which even the wicked were invited to share their song. When he conjured moral authority expertly in his work, that authority was derived not from his ability to embody normative values but from his drive to sing powerfully from a location outside of a moralistic middle-range. Cash had a unique genius for bridging and containing these locations within the mythic version of himself: not as contradictions, but as a total vision.
Tony is obviously a capable writer of prose. In this paragraph it is clear what he is trying to get us to believe. He tells us in the first sentence. In order to support his claim he uses a standard rhetorical move, namely, the appeal to authority (here, one step short of an appeal to God, namely, an appeal to Bob). He then explains what Dylan might have meant by "lost causes of the human souls" by describing the place Cash granted to sinners. It is because Cash's work does not exclude "the wicked" that the violence we find in his songs is not gratuitous.
You don't have to agree with Tony to grant that he has here composed a perfectly good paragraph. And if you go back and read it in its context, it should become immediately clear how a paragraph supporting the claim that "Cash's violence was never gratuitous" fits into his larger argument. It is a unit of that argument that had to be composed to function in precisely that larger context. If Tony had just just left it at the first sentence, assuming we would take his word for it, rather than Dylan's, or just left it at a quotation of Dylan, without explaining what that quote is supposed to mean for his own purposes, he would have accomplished very little.
But compare his accomplishment in prose with the following excerpt from a project he called "1001 Sentences":
Every successful sentence lessens one’s reliance on memory.
What we do we do because of what we didn’t.
Unimportant themes are thrust forward to protect the more important ones.
The sun is also in the wrong.
I am assured that this poem is actually myself or at least that part of me which demands always to be before the camera.
Sometimes freedom is found in the teeth of the ladder.
My career is distinguished by how shamelessly I judge my enemy (the reader).
I see everything in you.
The center of all ignorance is found to pulsate a few miles behind your eyes.
This is the work of the same writer. And while it consists of sentences, and is certainly as accomplished in its way as the paragraph about Cash, it is clearly not prose. We could, perhaps, imagine this as a kind of "after the fact outline" of the key sentences of a ten-paragraph essay. The sort of thing that would happen if we extracted only the most pregnant phrases from the Cash piece:
It is grieving for the downtrodden while ignoring how one’s own boot heel leaves a mark on their throats.
His violence was often excessive, it was never gratuitous.
This is not a generalized desire to be free, but a very specific lust for freedom.
"I had a friend who was playing guitar with him at the time."
This is not quite poetry, but it's getting there. One of the most important differences between Tony's paragraphs and his sentences is that his paragraphs are clearly about something, they "represent" something, namely, the music of Johnny Cash. But a sentence by itself does not do this. In fact, in "1001" Tony is intentionally undermining the ability of each sentence to be about anything specific, by putting it in the context of the others. We can imagine writing a paragraph around each sentence that would make perfect sense of it. This is plausible precisely because we know how the "aboutness" of those sentences that were originally about Johnny Cash was lost. We'd just be doing that sort of thing in reverse.
There's a homework assignment here. First, turn Tony's prose about Johnny Cash into 10 sentences of poetry. Next, write a ten-paragraph essay that uses ten of Tony's "1001 Sentences" as key sentences. This will teach you something about what prose is (and isn't), perhaps even something mildly provocative.