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How would you know if we are on a timeline where intervention from the future has changed the past? In our timeline, it hasn't changed.

That is: The original timeline is timeline A. Travelers from the future come back, intervene, and the result is timeline B. But to those on timeline B, nothing has changed - it just looks the way timeline B always looked.

(Unless the intervention is blatant - people show up in a flying saucer and use death rays to assassinate Hitler before he becomes Chancellor, say...)

yeah I'm thinking about it in the way that is assumed by the original author, with the idea that visitors from the future would be somehow identifiable.

We could as well be the result of a series of pranks perpetrated from time travelers from other saner timelines.

> It's sort of like the question 'why did life arise on Earth and nowhere else that we are aware of?' - the only reason we can ask the question is because we are the result of exactly the factors that would produce a consciousness that _could_ ask that question.

Sounds like the Anthropic principle, which is not accepted by all scientists: https://en.wikipedia.org/wiki/Anthropic_principle

It's the weak Anthropic principle - we find ourselves on a planet that supports life because we couldn't have arisen on a planet that didn't - which is necessarily true.

It is necessarily true, but it does not explain anything.