Multiverse: Gondwanaland

Robert Silverberg, "Christmas in Gondwanaland" IN Greg Bear and Gardner Dozois, Multiverse: Exploring Poul Anderson's Worlds (Burton, MI, 2014), pp. 215-244.

I have read some very good science fiction by Robert Silverberg (see image) but I always have problems with his time travel, sometimes big problems (see here). In Silverberg's Time Patrol story, Manse Everard and Daniel Ben-Eytan of the Time Patrol fly above a Gondwanaland on which every human being attending the Founding Convocation of the Patrol has been assassinated early during the Convocation. It follows that:

Everard and Ben-Eytan are in a timeline without a Patrol;
futureward along this timeline, a million years of history, unprotected by the Patrol, are altered out of recognition by time criminals;
therefore, by traveling futureward along this timeline, they cannot possibly arrive in a Prague, 1910, that they will recognize.

Yet they do precisely that. In Prague, they meet a team of colleagues with whom they will try to prevent the mass assassination. According to Anderson's stories, such a team would have to meet at a time before the event that they aim to prevent. If and only if they succeed will they be able to travel futureward into the familiar timeline protected by the Patrol.

Silverberg writes that, as Everard looked down on the scene of the assassination:

"...he knew that if the horrific event that had taken place in this convocation-hall at the dawn of time was allowed actually to happen, everything that he thought of as the history of the world was going to be altered." (p. 224)

But if he is in a timeline where "...the horrific event...had taken place...," then he is in a timeline where the horrific event had actually happened (he is not looking at a simulation) so he is in a timeline with an altered history. He can, if he travels back to a time before the horrific event, try to prevent that event but he cannot, from a time when he is looking at the accomplished event, travel futureward into his familiar timeline. And, if he could do that, then why would there be any need to prevent the horrific event?

I know that more than this is said in the story but I am deliberately focusing on one point at a time because everything gets too confused otherwise. Ben-Eytan says things like, "We exist and we don't exist." (p. 218) What does that mean? Each of us exists in a timeline in which we are born, live and die. Each of us does not exist in a timeline in which we are not born, the one exception (in the Time Patrol series) being that a time traveler might travel pastward, then return futureward into an altered timeline in which his birth has been prevented so that now he does exist in a timeline in which he was not born. But "We exist and we don't exist" is meaningless.

When Everard and Ben-Eytan were in Paris before traveling to Gondwanaland, Everard thought that Ben-Eytan's account:

"...didn't sound right. It was too glib. It sounded like the sort of thing that an instructor would tell a bothersome trainee at the Academy to shut him up when it was necessary to get on with the day's lesson. If the Patrol had been removed at its point of origin in the Cambrian, how could anything, anything at all, still be remotely the same here in twentieth century Paris? That bothered him very much." (p. 219)

Here, Silverberg states the problem with his own account. Saying that it bothers even Everard might be intended to reassure the readers that they are not alone in being bothered - if they are. A lot of readers don't seem to be bothered and even think that this sort of time travel narrative, e.g., in Doctor Who, makes perfect sense!

My impression of the Time Patrol Academy is that it is a place where instructors try to instruct trainees, not to shut them up. If this sort of question were dismissed glibly, then how would the Patrol function and what would the day's lesson be about?