To attempt to identify poetry and ideology too closely damages both poetry and whatever ideas it is being wedded to. Poetry becomes a mere tool for propaganda and the ideas being propagandized are shown as insufficient to stand on their own. As Kirk puts it, “No man is saved by poetry.” This is the crux of Eliot’s criticism of John Milton’s Paradise Lost, of which Eliot wrote “it is a glimpse of a theology that I find in large part repellent, expressed through a mythology which would have better been left in the Book of Genesis, upon which Milton has not improved” (SP, 263). Milton failed, according to Eliot, in large part because he did not know when to be a theologian and when to be a poet. 

David Withun, "Making Peace with the World: T. S. Eliot and the Purpose of Poetry"