1533 And 1885

Sometimes in Poul Anderson's texts, the difficulty of discussing time travel paradoxes becomes more evident. In London 1885, two Patrolmen, Everard and Vasquez, discuss a situation in Peru 1533 that Vasquez has just come from. A friar, secretly a Patrolman, and a cavalier had disappeared from inside the locked and guarded treasury where the Inca Atahualpa's ransom was being stored. Vasquez says:

"'When I left, the general idea was that sorcerers had been at work. Hysteria was building rapidly. It could have hideous consequences.'
"'Which are not in the history we learned,' Everard growled. 'How critical is that exact piece of space-time?'
"'The Conquest as a whole, certainly vital, a key part of world events. This one episode - who knows? We have not ceased to exist, in spite of being uptime of it.'
"'Which doesn't mean that we can't cease,' said Everard roughly. We can never have been, ourselves and the whole world that begot us. It's a perishing more absolute than death.'" (Time Patrol, p. 679)

If events in 1533 had altered subsequent history so that there was no Victorian London with a Time Patrol office in 1885, then Vasquez, far from ceasing to exist, would simply have arrived in a different version of 1885.

Perishing or ceasing to exist is not the same as never having been. On the contrary, anything that perishes or ceases has been. It makes no sense for Everard and Vasquez to fear that events in 1533 after Vasquez's departure from that year are going to cause them to cease to exist in 1885. Events in 1533 are not going to happen. They have already happened, back in 1533. And they did not prevent the existence of a Victorian London with a Time Patrol office in 1885. If they had done, then Everard and Vasquez would not have been there to talk about it.

Of course, it is conceivable that an undesirable timeline did diverge from 1533 but Everard and Vasquez are not in such a timeline and cannot be affected by the alternative course of events in such a timeline. There may be a point of view according to which the undesirable timeline is "present" whereas the Time Patrol timeline is "past" but that is not Everard's or Vasquez's point of view so they do not have to worry about it.