When Havig recounts how circumstances thwarted his attempts to change the past, Robert Anderson asks:
"'Does God intervene, do you think?'
"'No, no, no. I suppose it's simply a logical impossibility to change the past, same as it's logically impossible for a uniformly colored spot to be both red and green. And every instant in time is the past of infinitely many other instants. That figures.'" (p. 114)
We all know that either God does not exist or He does not run the universe by direct interventions. But why should He intervene? The propositions that Hitler was assassinated in 1942 in Timeline A and that Hitler was not assassinated then but instead committed suicide in 1945 in Timeline A are logically inconsistent. No one needs to intervene to prevent both propositions from being true. They cannot both be true.
The same logic applies to unknown events. It is not known whether a time traveler arrived at a particular time on a particular date in an unoccupied house. If he did not arrive there-then, then he will not succeed in arriving there-then. But, if he did arrive there-then, then he did arrive there-then. If p, then p. Not (p and not-p). (In logic, p is any proposition just as, in algebra, x or n is any number.)
6 comments:
Kaor, Paul!
Well, I believe God can and has intervened, not to change the past, but to change events in the futures following those interventions. Such as the miracles recorded at Lourdes. That would not logically be an impossibility.
And there were attempts at assassinating tyrants like Lenin and Hitler, but all of them, alas, failed.
Ad astra! Sean
For circumstances to always "happen" to frustrate attempts to change the past would require a "supernatural Time Patrol".
Mr Stirling,
Or at least it would require an amazing change in the laws of statistics which is why I think that time travel must be impossible, nonexistent or at least rare in an immutable timeline.
In the normal way of things, it is not necessary for circumstances to happen to prevent logical contradictions. Such contradictions cannot happen in the first place. Logical consistency can handle a few time travel journeys with either no paradoxes or only circular causality paradoxes - or maybe some causality violations: a man in a time machine appearing and preventing a meeting between the man and woman who would otherwise have been his parents is not logically contradictory, just counterintuitive.
Paul.
Kaor, to Both!
More and more I feel compelled to think alternate or parallel universes to be more likely or plausible than time traveling. That would seem to allow for events happening differently in many universes. E.g.: Universe A had a Sarajevo Assassination but Universe B did not.
Ad astra! Sean
Sean: there's a substantial physics argument for the "many worlds" (actually "many universes") hypothesis.
Kaor, Mr. Stirling!
I agree, and I've read books like Sean Carroll's SOMETHING DEEPLY HIDDEN, which argues for that.
Ad astra! Sean
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