According to Ezra Pound, the poet who started the Imagism movement:
It is better to present one Image in a lifetime than to produce voluminous works. . . .
This is the purpose of the poetic career, according to the Imagist - to create a single image that will outlive him. Pound believed that abstraction distracted from the presentation of the truth. Here is an example from him:
Don't use such an expression as 'dim lands of peace.' It dulls the image. It mixes an abstraction with the concrete. It comes from the writer's not realizing that the natural object is always the adequate symbol.
Thus, poets who wanted be successful - according to the Imagists - would get rid of all extra words, unneeded adjectives, and vague nouns. Instead, they would focus on presenting the truth in statements of clear vision.
Eliot does this in Prufrock. He begins with a description of city streets, uses metaphors that are concrete ("pair of ragged claws on the floors of silent seas"), and uses the narrative and dialogue of the speaker to show us a story of alienation. Eliot never states his theme - he allows the images of Prufrock to tell it for him.