Ong textbook:

"Lack of verifiable context is what makes writing normally so much more agonizing an activity than oral presentation to a real audience. The writer's audience is always a fiction. The writer must set up a role in which absent and often unknown readers can cast themselves. Even in writing to a close friend I have to fictionalize a mood for [him], to which [he] is expected to conform. The reader must also fictionalize the writer. When my friend reads my letter, I may be in an entirely different frame of mind from when I wrote it. Indeed, I may very well be dead. For a text to convey its message, it does not matter whether the author is dead or alive. Most books extant today were written by persons now dead. Spoken utterance comes only from the living."