I think that SSBlues has given a clearer exposition of the problem than I have, but I wrote this anyway, and I have attempted to address all of David's comments. But I would prefer that David respond to SSBlues post, rather than this one; or, in addition to this one, but hopefully, the problem of personal identity that SSBlues has raised is also sufficiently reflected in my following remarks:
What I meant by "one exists at all temporal parts" is no different to your recent statement (at the top of this page): "If eternalism is right, or if Platonia is right, then our brain states are present at multiple temporal locations."
I take it that we have been talking about the temporal parts of a single individual person, whose boundary conditions are his/her birth and death. Also, I take it that we have been attributing memories, interpretations, and illusory experiences to these same individual subjects.
I was merely following you in housing these static theories under the one roof, where you earlier stated:
"Each brain state at each time capsule in Platonia, just like each brain state at each temporal part under eternalism (different ontologies, same epistemologies) do NOT experience more than one time capsule or temporal part. Their respective brain states are eternally at their fixed time capsule in Platonia or at their fixed temporal part in the blockworld of eternalism. There is no passage in these ontologies of time. All the states, however, exist; in Platonia they exist in different time capsules, and in blockworld they exist at different temporal parts in a spatiotemporally extended object through a 4D space."
Also, given that we can rearrange Barbour's time capsules so as to accord with our illusory experience of succesive moments, or "put them in order", so to speak, this leads me to wonder why their disorder is even posited in the first place. I can only imagine that it must be for some logico-tactical reason. Or, possibly, to add an element of randomness to his orderly theory.
But there is the appearance, or the illusion, of this "single "I" that experiences passages." Therefore, how do you, if it is possible, distinguish this single "I" from the "vast multitude of "I's" in the eternalist perspective, each at its own spatiotemporal location"?
This is not how I view the proceedings. I think the problem results from your attempts to speak of an experience at a time, such as the "experience of succession": the comparison between past and present brain state configurations or temporal parts. Out of interest, where does one brain state configuration, or temporal part, end, and another begin? Isn't it you and your authors who must assume that we are wholly located at a present moment, when you claim that we can have the purported "experience of succession" (without any actual "succession of experiences") at any, and all, of our temporal parts? This is your authors' explanation of the illusion, anyway.
Okay, but why is my conscious perspective restricted to only one temporal part, and why does it appear to pass through successive temporal parts?
But this only makes sense if we do, in fact, pass through time as well. And, given that, from our conscious perspective, we do find ourselves at ever later dates in time, then how is it only an illusion that we pass through time? The comparison of present and past states can only provide the illusion if it is also assumed that the present moment is ongoing, and is not a static moment in time. So it seems that I can only have the illusion of a flow if there is a flow - at least from a conscious perspective - otherwise I can never find myself at a later date, where I can compare present and past memories, and think that something has passed. I don't see that the thought alone could provide the illusion, nor that the thought could arise if we didn't find ourselves to be conscious of ever-later (successive) moments, or temporal parts.
On the subject, how does a temporal part manage to distinguish its present memories (or its "notion of "now"") from its past memories? It hasn't accumulated memories by travelling from a past moment to the present moment, since any appearance of such is only an illusion. So, how would a temporal part draw the line between its present and its past memories, in order to compare them, if all that exists is a single configuration of its brain states at that time?