Eliot starts its analysis about literary production considering it in the context of the whole culture. As a matter of fact any text has always references to the immortal poets' greatest works.
Taken that assumption for sure, Eliot explains that he is not going to analyze adolescent works where there is a sort of "Mannerism", with a strict adherence to the models proposed by tradition.
On the contrary Eliot believes that only when an artist grows old he can innovate, because he has reached the awareness of the historical sense by "great labour".
As a matter of fact any literary work should be evaluated in relation to the historical sense the artist is able to convey. Any very innovative work hasn't got his meaning alone, it needs references for contrast and comparison to the other works of artists and poets. The references between the past and the present create a global order, so that the work may become timeless. When a work is set in a context, therefore it is temporal and become timeless at the same time. It gains the role of a traditional work of art.
Moreover a new traditional work of art modifies former works: it modifies the whole tradition as if it were a complete system. Thus it requires a readjustment by the previous culture to cohere in the perspective of the new system. Therefore the past is altered by the perspective of the present. This leaves the greatest artist a role of great responsibilities providing the world with the key to understand the cultural system.
Eliot surely analyzes the role of art in a very detailed way, but he paid the price to his age. He doesn't seem to be universal when he speaks about order and the coherence of the system of culture, at least he doesn't seem timeless, because nowadays the main trends of thought refuse the concept of order.
On the contrary Eliot anticipates several post-modern concepts: for example in the close of the essay he reminds us the important role of the intellectuals against the partial interpretations of the past that someone might build up. As a matter of fact intellectuals are the ones who have the power to adress common people in their reflections.
Following Eliot's suggestions Historical Revisionism, for example, would lose its role if the intellectuals gave with their works a responsible key of interpretation to culture.