"Those who practice this game forget that a book is more than a verbal structure or series of verbal structures; it is the dialog it establishes with its reader and the intonation it imposes upon his voice and the changing and durable images it leaves in his memory." (Borges)In his introduction to Wittgenstein's Tractatus, Bertrand Russell stated its central question as follows: "What relation must one fact (such as a sentence) have to another, in order to be capable of being a symbol for that other?" Though he is sometimes accused of forgetting it himself, it is important to point out that Wittgenstein was not suggesting that a sentence can symbolize a state of affairs independent of a mind to comprehend it. That is, one part of the "relation" between the sentence and the fact is a sentient being who reads and writes it.
"We make to ourselves pictures of facts," said Wittgenstein (T2.1). It is one of those sentences in the canon that is utterly simple and profound. Whether we are observing the fact directly or reading a sentence about it, we form an image of it—what Wittgenstein calls a "logical picture". This operation is absolutely crucial to understanding a text.
A sentence is not straightforwardly an arrangement of words that represents an arrangement of things (i.e., a fact). This can be easily seen in the case of a sentence that includes a pronoun. "It was lying on the sidewalk," for example. What this sentence represents will depend crucially on the context that determines the meaning of "it". Ultimately, however, the context will include the whole world of the reader, which determines the meaning of words like "sidewalk" and "lying". This world is part of the context of the fact that is a sentence. Understanding the sentence depends on the reader's ability to imagine this world. And writing a sentence, therefore, depends on the writer's ability to imagine the world of the reader.
The role of imagination in reading and writing, and therefore the role of imagination in scholarly work more generally, is not often enough acknowledged in my opinion. We take the capacity of a sentence to symbolize (i.e., stand for, i.e., represent) a fact for granted and do not give ourselves the time to imagine the world that our writing (and reading) implies. A text comes to represent, not any particular arrangement of facts, but our generalized authority as scholars. Reading the text does not become an occasion to imagine something but merely one to acknowledge the position of an author in a verbal structure.