Eliot wanted readers to focus on the poem itself when trying to understand what poetry was all about, in addition to the long tradition of poetry each poem belongs to. (He was a famous poet himself, after all. Poets are as poets do.)
One of his most famous essays to this effect, "Tradition and the Individual Talent," was published in The Sacred Wood. In this one he argues:
No poet, no artist of any art, has his complete meaning alone. His significance, his appreciation is the appreciation of his relation to the dead poets and artists. You cannot value him alone; you must set him, for contrast and comparison, among the dead. I mean this as a principle of aesthetic, not merely historical, criticism.
What do you think Eliot means by saying that no artist "has his complete meaning alone"? If you were using Eliot's style of "aesthetic" criticism to analyze, say, The Waste Land, how would you go about it? How would you give this doctor a little bit of his own medicine, huh?
And to get even more meta on you, we want to ask: In order to understand Eliot's poetry, do you think we need to know his theories about poetry?