... Son of man,
You cannot say, or guess, for you know only
A heap of broken images, where the sun beats,
And the dead tree gives no shelter, the cricket no relief, (The Waste Land, T. S. Eliot)
Epistemology is the study of the nature and origin, the methods and limits of human knowledge (Random House Dictionary). One of the questions asked within the study of epistemology is "What are the necessary and sufficient conditions of knowledge?" (Stanford Encyclopedia of Philosophy).
The above early quotation from Eliot's The Waste Land illustrates his interest in the questions surrounding knowledge and his philosophy of the answers. In paraphrase, the quote is saying that we can not know because what we perceive (which is the root of knowledge: perception) is broken, glaring, dead bits of reality and of that which is true. Thus Eliot posits that we cannot know.