How do we devotees of the Plumbline defend against an understandable first impression, that to seek a "middle way" is a ticket to mediocrity - a boring compromise? Isn't poetry all on fire? Isn't it a stand against exactly the stolid "workmanship" that grinds everything down to a levelling sameness?
One could do worse, in reply, than turn to Guy Davenport's famous essay "The House that Jack Built" (collected in The Geography of Imagination - which you can find online). Starting with some wide-ranging speculations in John Ruskin's Fors Clavigera, Davenport examines the deep labyrinthine craft of Joyce, Pound, WC Williams & Zukofsky as "Daedalian" makers - poetic builders. Davenport's little essay opens up a view onto a veritable abyss of supple literary masonry.
The notion of the plumbline as a measure of balance or equilibrium - a measure which allows the artist to devise syntheses & combinations of seemingly discordant materials - & thus to delve deeper into whatever subject or theme he or she has taken on - I think this is also an aspect of what we might be concerned with, here. All of these artists were interested in fashioning capacious works - that is, capable of reflecting experience and reality in "the outdoors" - beyond the confines of art itself. Once a "fitting" balance between matter & style is forged, the artist is then able to move forward to further symbolic syntheses. (For example, in Joyce's Dubliners, as Davenport shows, we have 2 things in balance : tales of very realistic grubby Dublin on the surface, and a symbolic labyrinth of literary meanings underneath, whose moral and aesthetic valences give weight to that very surface.) So, in this sense, the "plumbline" is also a sort of compass, or gyroscope - a means for traveling further, deeper.
The poem as conjunction-of-opposites... when was a wedding night ever boring (even if - God forbid - it goes wrong)?
There is a world dimensional
For those untwisted by the love of things
Irreconcilable... - Hart Crane