In Poul Anderson's Old Phoenix multiverse and in some other fictional multiverses, persons and events that are fictional in one world are real in another. Is this because every possibility exists or because writers can mentally tune in to other universes? Writers exercise creative imagination but does this imagination tune in to other universes?
A work of fiction can contain contradictions. Thus, the fictional world cannot exist exactly as described. However, this shows that the author's mind distorts the information that it receives. Dr Watson's narratives are published in his world and in ours so was Arthur Conan Doyle mentally linked to Watson? If so, then he missed the Time Patrol that coexists with Holmes and Watson but then so did Watson.
In the Time Patrol timeline, Tacitus Two is alternative history although it was not written as such. The fact that such divergent texts are not frequent shows that the circumstances of its origin were unusual. Tacitus One, known to historians, is incomplete: only four books and part of the fifth from an original twelve. Time travellers recovered the entire text but the Time Patrol has also discovered Tacitus Two and the narrative line of this alternative version does not diverge from Tacitus One until shortly after the scene where the surviving fifth book had broken off. Janne Floris asks whether this is coincidence and Manse Everard comments that it is kind of spooky. Something is always left unexplained.