The Practice Of Variable Reality

Recent combox discussion (See Counter-Intuitive Or Contradictory II here) shows that readers of Poul Anderson's Time Patrol series can have very different understandings of it.

The facts are clear:

time travel is possible;

time travelers want to be able to visit the past and to return to their version of the present;

however, there is always the danger that they will return to the wrong version of the present;

therefore, the Patrol exists either to prevent or to correct historical alterations - if possible.

That is the practice. Is there a coherent theory to account for it? Relativity theory and quantum mechanics are mutually incompatible although both work. Maybe a unified theory of reality is a limit that can be approached but never reached?

In the early Time Patrol series, the only cause of historical alterations mentioned is "extratemporal intervention," the actions of time travelers. One way to prevent such interventions would be to ban time travel. However, people want to time travel and the travel itself is part of the sequence of events that leads to the post-human Danellians who found the Patrol.

Later, a second cause of alterations is discovered: random quantum fluctuations in space-time-energy. The ultimate antagonist is not time criminals but temporal chaos and time travel is necessary to counteract chaos.

The experiences and actions attributed to Time Patrollers are consistent and conceivable even though I have problems with the way that they conceptualize them.