Every text constructs a reader for itself. (You, my friend!) Whenever writers write, it is with the assumption that they are addressing others who do not know what they are explaining. Each time a narrator “recounts facts which he knows perfectly well,” writes Barthes, we find “a sign of the reading act, for there would not be much sense in the narrator giving himself information” (“An Introduction” 260).
Let’s test this assertion by considering a couple of potential exceptions. How about a note to self, like “Don’t forget to call Dad on Father’s Day”? Wouldn’t that be a “narrator giving himself information”? Actually, I would be writing to a future me who may have forgotten, therefore, a constructed reader who does not know.