In his 1821 essay "A Defence of Poetry," Percy Shelley says that "poetry is connate with the origin of man." This is an easy claim with which to sympathize. After all, language seems to have been a central element in human evolution. And language is inherently referential and, therefore always seems to hold the promise of poetry in it. Of course, these issues raise the perennial, seemingly unsolvable problem, of how one defines poetry. Shelley wanted to defend poetry so he had to, at some level define it. But by telling us that "poetry is connate" with our origins, he is really just telling us that poetry is an unavoidable element of language, we cannot avoid it even if we wanted to. But because of the referential nature of language, the continual metaphorical element on which it seems to operate, it seems almost pointless to attempt to distinguish poetry from any other part of language use. In other words, if language in the many ways that we use it, is continually relying on metaphor, or to say it another way if metaphor is at the heart of language, then it seems to be a purely academic matter to attempt to distinguish between poetry and prose. At a wider level, the problem was defined by Derrida when he reminded us that there is no 'transcendental signified." This is just another way of saying that, while language seems to refer to things in the world, it can only, at best, reach out toward the world, it cannot provide us with certitude.
I think, at some level, many people feel the uncertainty of the world (and language's ability to pin it down) instinctively. At a practical level, we hope that, say, a set of written instructions will be clear enough and be a useful aid to performing whatever task we are setting out to perform. But many of our linguistic experiences are fraught with imprecision, and certainly our so-called literary ones. We accept it. In fact we usually relish in it. If we were searching for certitude, we surely wouldn't be reading Henry James or Emily Dickinson. And though many wearisome English teachers might insist to their students that James' Golden Bowl or Dickinson's "I felt a Funeral, in my Brain," express certain meanings, such claims are contrary to the nature of literature if not language. In other words, I think that we read not in a search for certitude, but precisely because life is uncertain.
But to return to Shelley's Defence of Poetry," I am sure that Shelley would have been comfortable with pushing aside any distinctions concerning poetry and other forms of literature. Shelley was using the term poetry not to indicate a type of literature so much as he was using it as a word for the act of human dreaming. That is why Shelley says that poetry may be defined as "the expression of the Imagination." And in a remarkable foreshadowing of 20th century discourse, Shelley goes on to tell us that "language is virtually metaphorical; that is, it marks the before unapprehended relations of things, and perpetuates their apprehension, until the words which represent them become through time signs for portions or classes of thoughts, instead of pictures of integral thoughts."
Dreamers express their dreams, and prophets are only prophets to the degree that they express their visions. And like most poets, Shelley was a dreamer, and certainly a prophet of sorts.
But what does it matter if we dispense with literary distinctions? Other than certain conveniences stemming from taxonomy, there seems to be few, if any reasons to advocate for such distinctions. And there seems to be plenty of reasons to argue against them, the dangers of elitism being amongst the most important. And it is no surprise that Shelley's essay contains the reminder that "the principle of equality had been discovered and applied by Plato in his Republic." If political and social equality is supposed to be of such importance to us, why not apply it here, to literary endeavours? Even when we apply rather nebulous categorical boarders to literature types, we run risks of exclusion and devaluation. I have seen this first hand on many occasions. It is a strange phenomenon to listen to a supposed literary authority struggle to defend syllabus choices based on some abstract and painfully woolly categorical argument that ends up with them inadvertently defending an elitist or sexist, if longstanding, structural convention. And so, interesting work is conveniently marginalized and excluded from the very people who should see it. Such exclusion often targets women or other marginalized voices out of hand, but can also exclude groups of work that don't fit into the standard categories. This is true of, for example, essays or just works that don't fit clearly into regular conventions such as Carlyle's Sartor Resartus, Thoreau's Walden, or Leigh Hunt's The Honey Jar. And for more modern examples just think of most of Andre Breton's work like The Lost Steps, Mad Love, and Nadja. (Incidentally, this is also true of a number of other surrealist authors as well as some of the writers from whom they drew inspiration like the Comte de Lautréamont.)
Anyone who has taken a university English course, and has any sense of natural skepticism or a previous interest in some marginalized literary work, knows with what fervour professors can muster a categorical defence. Few phenomena have done more to alienate people from literary enjoyment or study.
To return to the subject of Shelley's Defence, it is interesting to me that he wraps it up with the now famous declaration that "Poets are the unacknowledged legislators of the world," because if it is true, it is remarkable how many impediments are thrown in the way of us garnering the insights of that legislation.
Here's a thought - next time someone asks you "what is poetry?" step on their foot and when they cry out in pain say, "That! That is poetry."