The point is philosophical. I know that what I am looking at is a house because I am already familiar with things that look more or less like it and are houses. This is what enables me to say that the particular house I am looking at is a big house, an ugly house, a modern house, and so on. The same thing happens when I read a poem: I relate it to all the other poems I have read—in the head of an ideal reader, to all the poems that have ever been written. Past poems condition my response to any new poem. And the really new poem conditions my response to all the poems that preceded it. After “Prufrock,” the Inferno is, ever so slightly, a different poem. After I see a house by Marcel Breuer, my own house looks, ever so slightly, different.Seems to me the same could apply the Heidegger, also working in the 1920s, like Eliot, Pound, and Joyce. He casts his contributions in terms of the tradition, and after him the tradition is understood differently. Despite his de-structuring being construed as an origin for multifaceted post-modernism, Heidegger himself worked as a modernist, in this literary sense.
Eliot argued that, since this is the case whether a poet is conscious of the tradition or not, he or she might as well be conscious of it. The more complete the poet’s saturation in the whole of literature, the more genuinely new that poet’s work is likely to be—that is, the more powerfully it is likely to affect the old.