reading more Elder Olson, one of the Chicago critics (On Value Judgements in the Arts, and Other Essays). recommended, if you can get ahold of it.
He analyses Yeats' "Sailing to Byzantium" (fine); writes about Moore, Stevens, Bogan, Wylie, others of that era; tries to delimit boundaries of what a "lyric poem" is (great essay)... in so doing, extends some of Aristotle's approaches in the Poetics (beyond tragic/dramatic poetry).
In the Yeats essay, he looks for the principle, in a particular lyric poem, which plays a role analogous to that of plot in a drama. & finds it.