from Robert Alter, The Art of Biblical Poetry, chapter three

The fact is that poetry in general involves, necessarily, a linear development of meaning, which means that in one respect it is a linear form of thinking or imagining. “Those images that yet/fresh images beget,” Yeats wrote in one of his most famous poems about art and the imagination, and that approximately, is the way most poems would seem to work: one image suggest a related one, or a further manifestation of the same underlying image; one idea leads to a cognate or consequent one; one pattern of sound, interinvolved with a particular semantic direction, leads to a similar pattern that reinforces some underlying similarity of suggestive antithesis of meaning.