The key quotes for me are:
1. T. S. Eliot in The Little Gidding:
...And every phrase
And sentence that is right (where every word is at home,
Taking its place to support the others,
The word neither diffident nor ostentatious,
An easy commerce of the old and the new,
The common word exact without vulgarity,
The formal word precise but not pedantic,
The complete consort dancing together).
Every phrase and every sentence is an end and a beginning...
2. Alexander Pope in his Essay on Criticism:
True ease in writing comes from art, not chance,
As those move easiest who have learned to dance.
'Tis not enough no harshness gives offense,
The sound must seem an echo to the sense.
3. I once formulated a General Theorem of Poetry:
(Sound > Sight > Trope > Metaphor > Subject)
(Sound = Sight = Trope = Metaphor = Subject)