Tinkering With Reality

In Poul Anderson's The Shield Of Time (New York, 1991), chapters are unnumbered. Each is headed by a year date, sometimes by the same year date. Thus, we must distinguish between 1985 A.D. pp. 11-16 and 1985 A.D., p. 123. These opening and concluding chapters of Part Two are set in the same year but in different timelines. On pp. 11-16, a mysterious Russian captain gives Private Garshin the casket containing the Bactrian letter whereas p. 123 informs us that the Patrol has cancelled that event so that Garshin does not meet the captain.

(This explains something else. The letter saying that Euthydemus had sallied out of the city was a fake. Thus, the Exaltationists did not have any opportunity to help Antiochus to kill Euthydemus on a battlefield after all.)

If the events of pp. 11-16 have been annulled, then so have the events of 1987 A.D., pp. 66-76, when Shalten informed Everard of the Bactrian letter. However, Everard traveled to 209 A.D., pp. 17-25, 34-41, 47-65, 77-94, 102-118, with memories of the Bactrian letter and therefore returned to the twentieth century with those memories. It is therefore redundant for Shalten afterwards to meet Everard in 1902 A.D., pp. 119-122, and say:

"In your position among us, you need to know the whole truth. For you to learn it later in this century could pose a hazard. Causational loops can be very subtle. Your experiences and accomplishments in Bactria must continue to have happened. Therefore you must be informed well pastward of our preparations for them.'" (p. 122)

Shalten is getting all mixed up. No annulment of events in 1985 can affect what Everard did two millennia earlier. And, as already argued, since Everard took his memories of the Bactrian letter to 209 BC, those memories returned with him even though the event in which he was informed of the Bactrian letter has been cancelled.