You cannot claim that such a perfect simulation liteally just is going back in time, because back in time there was no outer part.
You’re not justified in asserting that, for the same reason that your copy in a (correct, accurate) simulation of the moment when you wrote the comment would not be justified in asserting it. You can’t tell there’s no outer part of the universe, because if you could then it would be a part of the universe. Your simulation can’t tell there’s no outer part to its (simulated) universe, because then the simulation wouldn’t be correct and accurate.
I am justified in asserting that simulation is not, in principle, time travel. I may not be justifieid in asserting that I am not currently in a simulation. That is a different issue.
However perfect the inner part is, it is not the same as the historic event because the historic event did not have the outer part.
False. The outer part is irrelevant to the inner part in a perfect simulation.
You cannot claim that such a perfect simulation literally just is going back in time, because back in time there was no outer part.
I am justified in asserting that simulation is not, in principle, time travel.
You are of course right about this statement. It’s not time travel (for “normal” definitions of time travel), since nobody actually traveled through time within one of the universes.
But the precise claim seems to me to have shifted between answers, or at least the way we interpreted them did at each step.
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. 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. So the question is not quite counter-factual, but neither is it about a known (or even knowable) fact. For both the simulated and the historical observers, the presence or absence of an external universe is perfectly hypothetical (or perfectly non-testable, assuming a perfect-enough simulation).
Any “property” of the events (the historical and the simulated one) that can be compared will give the answer “equal”. You (the “real” you) can’t say, for example, “there is an outside-simulated-universe observer of the simulated event, but there was no outside-historical-universe observer of the historical event, so the two events are distinct”, because you can’t (by the assumption that the simulation was perfect enough) have any evidence in favor of the emphasized part of the statement.
I think this is something similar to that between classical and constructivist logic. That is, the answer depends on if your definition of sameness (“same events” in this case) is that
a) Every property can be shown to be identical, or
b) No property can be shown to be distinct.
If it’s (a), then you can’t justify saying that the two events are not the same, nor can you justify saying that they are the same, because there are properties that cannot be compared, so you can’t find out if they’re the same.
If it’s (b), then it follows from the assumptions that the two events are the same. (I take “However perfect the inner part is” to mean that it could be perfect enough that no observation made in the simulated universe is (or even the stronger version, could be) able to give information about the simulating universe’s presence.)
In the (b) case, note that (the historical) you can’t use your knowledge of the simulation to get around this. If the simulation is run for long enough, it will itself contain in its future a you simulating its own history, etc. Even if you stop the simulation before it reaches that point, you can’t claim that its timeline is shorter than yours, because it might be restarted in your future (and potentially catch up).
Of course, you can run a perfect simulation of an event and then intervene in the simulation in a way you remember to be different from your past. But I don’t know if you can design a change that would not require you to run the simulation infinitely long, so as to make sure its future doesn’t contain someone like you (i.e., that there’s no weird consequence of your change that leads to a simulated you that has the same memories as the historical you at the point when you made the simulation diverge, because he doesn’t remember his history correctly). Even if you turn the simulation off, I think that as long as you remember enough about it to be justified in making this kind of claims about it, it could be restarted in your future.
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.
You’re not justified in asserting that, for the same reason that your copy in a (correct, accurate) simulation of the moment when you wrote the comment would not be justified in asserting it. You can’t tell there’s no outer part of the universe, because if you could then it would be a part of the universe. Your simulation can’t tell there’s no outer part to its (simulated) universe, because then the simulation wouldn’t be correct and accurate.
There are turtles all the way down.
I am justified in asserting that simulation is not, in principle, time travel. I may not be justifieid in asserting that I am not currently in a simulation. That is a different issue.
You are of course right about this statement. It’s not time travel (for “normal” definitions of time travel), since nobody actually traveled through time within one of the universes.
But the precise claim seems to me to have shifted between answers, or at least the way we interpreted them did at each step.
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. 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. So the question is not quite counter-factual, but neither is it about a known (or even knowable) fact. For both the simulated and the historical observers, the presence or absence of an external universe is perfectly hypothetical (or perfectly non-testable, assuming a perfect-enough simulation).
Any “property” of the events (the historical and the simulated one) that can be compared will give the answer “equal”. You (the “real” you) can’t say, for example, “there is an outside-simulated-universe observer of the simulated event, but there was no outside-historical-universe observer of the historical event, so the two events are distinct”, because you can’t (by the assumption that the simulation was perfect enough) have any evidence in favor of the emphasized part of the statement.
I think this is something similar to that between classical and constructivist logic. That is, the answer depends on if your definition of sameness (“same events” in this case) is that
a) Every property can be shown to be identical, or
b) No property can be shown to be distinct.
If it’s (a), then you can’t justify saying that the two events are not the same, nor can you justify saying that they are the same, because there are properties that cannot be compared, so you can’t find out if they’re the same.
If it’s (b), then it follows from the assumptions that the two events are the same. (I take “However perfect the inner part is” to mean that it could be perfect enough that no observation made in the simulated universe is (or even the stronger version, could be) able to give information about the simulating universe’s presence.)
In the (b) case, note that (the historical) you can’t use your knowledge of the simulation to get around this. If the simulation is run for long enough, it will itself contain in its future a you simulating its own history, etc. Even if you stop the simulation before it reaches that point, you can’t claim that its timeline is shorter than yours, because it might be restarted in your future (and potentially catch up).
Of course, you can run a perfect simulation of an event and then intervene in the simulation in a way you remember to be different from your past. But I don’t know if you can design a change that would not require you to run the simulation infinitely long, so as to make sure its future doesn’t contain someone like you (i.e., that there’s no weird consequence of your change that leads to a simulated you that has the same memories as the historical you at the point when you made the simulation diverge, because he doesn’t remember his history correctly). Even if you turn the simulation off, I think that as long as you remember enough about it to be justified in making this kind of claims about it, it could be restarted in your future.
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.