Jonathan Mayhew affirms the notion that poetry aspires to the condition of music, arguing specifically that "poetry is closer to music than it is to 'literature' as conventionally defined." Since Walter Pater's original assertion was that all art aspires to that condition, in making this distinction between poetry and "literature"--which encompasses mostly fiction--Jonathan must be insinuating that fiction is not finally "art" at all. Indeed, he explicitly suggests that the novel is "centered on the mimetic portrayal of society on the broad canvas," which itself implies that fiction has primarily a sociological or documentary function. And in further asserting that this association with music would make poetry "one of the arts," he seems to be implying that "literature as conventionally defined" is not.
I think that Jonathan is probably right that fiction as "conventionally defined" by many readers and critics is not first of all regarded as art, and is precisely distinguished from poetry by the latter's more apparent homologies with music. Fiction is considered by too many to be a mode of discourse separable from nonfiction in its insistence on communicating indirectly, but otherwise still a mode of cultural, moral, or political description and reflection, another way of "saying something." For these people, to claim that fiction is, or ought to be, more akin to poetry in its aspiration to music is to trivialize it, deprive it of its mandate to "engage" with the "real world." For others, such a connection would inflate fiction beyond its actual merits, which are limited to its role as a medium for spinning a yarn.
Decoupling poetry and fiction as the Siamese twins of literature thus might have the beneficial effect of either redefining "literature" as that writing which does aspire to the condition of art by invoking a comparison with music or of sending the term into disuse altogether. The former would allow those who favor fiction-as-discourse to continue mining works of fiction for nuggets of "meaning" without being nagged by those favoring fiction-as-art about all that fol-de-rol known as "aesthetics." They might be hesitant to lose the term because by now it does confer an honorific status on the texts they examine--and thus also on their own endeavor as critics--but ultimately their interest is in literature as illustration, not in the integrity of literature itself, so they really would be able to keep doing what they do now even if fiction is finally identified as just another cultural form without the burden of being "literary."
If the latter, the abandonment of the term as an umbrella concept loosely uniting the primary modes of "creative" writing, were to occur, perhaps we might return to the use of "poetry" as a designation for all imaginative writing, a state of affairs that obtained before both "plays" and "novels" broke off from poetry to become separate forms of imaginative expression and before "poetry" became almost exclusively identified as lyric poetry. Speaking for myself, I would find this development heartily welcome, as it would allow some writers of fiction--those who think of themselves as artists rather than commentators, or simply entertainers, to align themselves more with poets and poetry without necessarily writing what is now called "poetry" per se. Fiction might become more "poetic" not by emphasizing conventional figurative language--which is what most reviewers identify as "lyricism" in fiction--but simply by implicitly acknowledging its own status as an artificial construction of language. Such traditionally constitutive elements of fiction as "plot," "character," or "setting" might remain as notional devices, but would recede in importance to the structural patterning of language the author has employed.
Already, of course, the boundaries between "prose" and "poetry" have become blurred, especially among contemporary poets. Moreover, there have always been fiction writers who have conceived their work to be "poetic" in the sense I have just described. (A good case could be made, for example, that the fiction of Gilbert Sorrentino was always more a variation on his work as a poet than an adaptation of the novel "as conventionally defined.") But either a further blurring of the lines or a further reinforcement of the lines so that "the mimetic portrayal of society on the broad canvas" isn't the default definition of "literature" could each bring a refreshing clarity to debates about the nature of literary art and its relationship to the other arts.