Needless to say, you gotta read da book to get da full treatmemt.
RS Crane quietly, succinctly surveys the last few many hundred yrs of poetry criticism, & finds that, despite all the excellencies, dey most of em summat missed the point.
Poetry remains an undiscovered moon.
Here's the conclusion to the section I quoted earlier:
"It is easy to see, therefore, why the critic who uses this language is necessarily restricted, in his selection of attributes for poetry or individual poems, to such characteristics as have clear counterparts or logical contraries in the non-poetic discourse which he takes as the other term of his comparison. This is not to say that the method is incapable of differentiating poetry, as poetry, from other things or of serving as a basis for practical criticism of a highly particularized and perceptive sort. It is, however, to say that the discriminations it permits between poetry and other forms of writing or between the various kinds of poetry are such - and such alone - as can be arrived at by asking what characteristics among those possible in discourse are here present and in what special modifications and combinations. It is not a method, in other words, that allows the critic, as Aristotle's method does, to consider poems in their peculiar aspect as distinct kinds of concrete wholes, of which the special character, as poetic wholes, is determined by internal principles of construction that have, at least as far as imitative poetry is concerned, no strict parallels in philosophy, science, rhetoric, or history." [pp.93-94]