Symmetrical Questions

There is a symmetry to two questions asked in Poul Anderson's Time Patrol series:

Should Hilter's birth be prevented?

Should the death in the War of a Time Patrolman's fiancee be prevented?

To a time traveller, these are essentially the same question although they involve preventing a birth and a death, respectively. Is it ever right to change the past - assuming that it can be changed? A changeable past is one premise of the Time Patrol series.

The first time Charles Whitcomb raises the second question, he formulates it in terms of killing Hitler:

"'I'm not allowed to go back and shoot that ruddy bastard Hitler in his cradle. I'm supposed to let him grow up as he did, and start the war, and kill my girl.'"
-Poul Anderson, "Time Patrol" IN Anderson, Time Patrol (Riverdale, Ny, 2006), pp. 1-53 AT 2, p. 16.

However, when Whitcomb does try to save Mary, he attempts only to prevent her from visiting a neighbour's house that is to be bombed. There are two issues here:

on the one hand, the Patrol forbids any time traveller to change the course of history, e.g., by killing Hitler in infancy;

on the other hand, it would not change history if one Mary Nelson had lived in London from 1850 to 1900 whereas another Mary Nelson went missing and was thought to have been killed by a bomb near a neighbour's house in 1944.

Nevertheless, the second situation can exist only if, behind the scenes, Whitcomb and Everard have rescued Mary from 1944 and transported her to 1850 and the Patrol forbids any such meddling because of the wider effects that it could have. However, there may be exceptions in such individual cases whereas there cannot possibly be an exception to the prohibition of killing Hitler. Because of variable reality, the Patrol can have records of events that did not happen and can also encounter events that have not been recorded. In this case, the Patrol has two contradictory records:

Charles and Mary Whitcomb lived in Victorian London;
Mary died in 1944 and Charles, remaining a bachelor, was killed on active duty with the Patrol.

These two sets of events could have been left in existence. There would have been two versions of Charles and Mary in a single timeline. However, a Danellian explains that:

"...as even the smallest paradox is a dangerous weakness in the space-time fabric, it had to be rectified by eliminating one or the other fact from ever having existed." (6, p. 52)

Because of Everard's intervention:

Charles and Mary Whitcomb lived in Victorian London;
Mary is presumed killed by a bomb near the home of the Enderby family who, however, were at Mary's house at the time and were not killed (this is a change);
Charles Whitcomb disappeared in 1947, presumed drowned (another change).

The Danellians find these small changes preferable to the original discrepancy.

Here is a related question. When Carl Farness' Gothic leman has died in childbirth because of an aneurysm of the cerebral artery, Carl asks:

"'Suppose we went downtime of her pregnancy...We could bring her here [to 2319], fix that artery, blank her memories of the whole trip, and return her to - live out a healthy life.'"
-"The Sorrow of Odin the Goth" IN Time Patrol, pp. 333-465 AT p. 376.

He is reminded that the Patrol does not change but preserves the past. But there are other complications. By preventing Jorith's death, Carl would have prevented himself from going to 2319 for help... Either there would now be two Carls, one who had helped to fix Jorith's artery and another who had not needed to do so - unless the Carl who attended to birth now no longer existed because the timeline had been changed by the fixing of the artery -, or, if Carl was prevented from setting off to 2319 to get help, then he would also be prevented from arriving in 2319 to get help. This gets too complicated.