With respect to whether or not the simulated event is the same as the past event in the universe hosting the simulation, I’d say the matters are less clear.
I think it is clear enough. “Is” usally means “is objectively”, not “appears to be so from the perspective of a subject”. It has been stipulated that there is a state of the univere S1 followed by a subsequent state S2 that includes a simulation of the state S1. That is enough to show, not only that no travel has occured, but that
the state of the universe S1 has not been recreated because the state of the universe at T2 is S2 and S2 =/= S1.
First, the question is somewhat unclear: neither the simulated participants nor the historical ones can tell if there’s a outside universe simulating their own’s.
That involves a shift from what is going on to what seems to be.
So the question is not quite counter-factual, but neither is it about a known (or even knowable) fact.
The original scenario simply stipulated that certain things were happening, so where does knowabiliy
come in?
Any “property” of the events (the historical and the simulated one) that can be compared will give the answer “equal”.
But that is irrelevant, because the original scenario stipulates that they are not.
With respect to whether or not the simulated event is the same as the past event in the universe hosting the simulation, I’d say the matters are less clear.
I think it is clear enough. “Is” usally means “is objectively”, not “appears to be so from the perspective of a subject”. It has been stipulated that there is a state of the univere S1 followed by a subsequent state S2 that includes a simulation of the state S1. That is enough to show, not only that no travel has occured, but that the state of the universe S1 has not been recreated because the state of the universe at T2 is S2 and S2 =/= S1.
(Emphasis mine.)
I think that is the root of our disagreement. I don’t think you’re supposed to just accept the “usual” meaning of the word “is” when you’re discussing unusual situations, and in this particular case I thought we were doing just that. (I.e., I thought we were using an unusual scenario to explore the possible meanings of “equality”, rather than using a certain meaning of “equality” to explore an unusual scenario. That was just my thought, I don’t mean you’re wrong if you were arguing a different issue, just that we failed to agree what we are talking about.)
My reading of the original scenario agrees with the italicised part of your summary, but not the rest. My claim is not that S2 equals S1, but that the simulation of S1 contained in S2 (call it S1b), could contain an event (call it Eb) that is equal with an event E contained in S1 that precedes the running of S2, for some useful definitions of “equal” and choices of E. Note that the original scenario doesn’t say that there is no S0 in which S1 is a simulation.
(I also suggested the stronger claim that, given a good enough simulation, it could also be possible for S1b to actually equal S1, though our universe might not allow the creation of a “good enough” simulation. Or, more precisely, that there are useful meanings of “equality” that allow such scenarios, and even that there might not be a consistent meaning for “equal” that don’t allow this in any possible universe.)
I think the root of your disagreement is an unstated assumption that “Sy follows (in time) Sx” implies “Sy =/= Sx”. That is usually true, but I don’t think it should be accepted without justification in unusual cases, such as those containing time loops or (almost-)perfect simulations (which could mean the same thing for some kinds of universes).
But what’s the mileage in the claim that you have an approximate reproducion of a moment in time? A battel re-enacment or historical move would cound for some values of “approximate”. That’s a long way from time travel.
I think the root of your disagreement is an unstated assumption that “Sy follows (in time) Sx” implies “Sy =/= Sx”. That is usually true,
If you are saying Sx and Sy are universal states, then you would need a simulator that somehow sacrifices
itself to in generating the simulated state.
I think it is clear enough. “Is” usally means “is objectively”, not “appears to be so from the perspective of a subject”. It has been stipulated that there is a state of the univere S1 followed by a subsequent state S2 that includes a simulation of the state S1. That is enough to show, not only that no travel has occured, but that the state of the universe S1 has not been recreated because the state of the universe at T2 is S2 and S2 =/= S1.
That involves a shift from what is going on to what seems to be.
The original scenario simply stipulated that certain things were happening, so where does knowabiliy come in?
But that is irrelevant, because the original scenario stipulates that they are not.
(Emphasis mine.)
I think that is the root of our disagreement. I don’t think you’re supposed to just accept the “usual” meaning of the word “is” when you’re discussing unusual situations, and in this particular case I thought we were doing just that. (I.e., I thought we were using an unusual scenario to explore the possible meanings of “equality”, rather than using a certain meaning of “equality” to explore an unusual scenario. That was just my thought, I don’t mean you’re wrong if you were arguing a different issue, just that we failed to agree what we are talking about.)
My reading of the original scenario agrees with the italicised part of your summary, but not the rest. My claim is not that S2 equals S1, but that the simulation of S1 contained in S2 (call it S1b), could contain an event (call it Eb) that is equal with an event E contained in S1 that precedes the running of S2, for some useful definitions of “equal” and choices of E. Note that the original scenario doesn’t say that there is no S0 in which S1 is a simulation.
(I also suggested the stronger claim that, given a good enough simulation, it could also be possible for S1b to actually equal S1, though our universe might not allow the creation of a “good enough” simulation. Or, more precisely, that there are useful meanings of “equality” that allow such scenarios, and even that there might not be a consistent meaning for “equal” that don’t allow this in any possible universe.)
I think the root of your disagreement is an unstated assumption that “Sy follows (in time) Sx” implies “Sy =/= Sx”. That is usually true, but I don’t think it should be accepted without justification in unusual cases, such as those containing time loops or (almost-)perfect simulations (which could mean the same thing for some kinds of universes).
But what’s the mileage in the claim that you have an approximate reproducion of a moment in time? A battel re-enacment or historical move would cound for some values of “approximate”. That’s a long way from time travel.
If you are saying Sx and Sy are universal states, then you would need a simulator that somehow sacrifices itself to in generating the simulated state.