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As a solution to the problem of the subjective passage of time, J. W. Dunne proposed an infinite hierarchy of time dimensions, inhabited by a similar hierarchy of levels of consciousness. Dunne suggested that, in the context of a "block" spacetime as modeled by General Relativity, a second dimension of time was needed in order to measure the speed of one's progress along one's own timeline.

Sound exactly like the Kantian reasoning for saying that time and space are apriori, and space doesn't exist independently of the observer, meaning it's not based on anything logical. It's just a metaphysical claim. I was wondering if Dunne's suggestion or claim had a more logical ground.

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    That claim about general relativity is completely bogus. Time in GR is different for different frames, but it always has one dimension no matter what frame you choose. The fact that time in one frame is different from time in another does not mean time is "2 dimensional" - it's rather more like writing the same vector in different bases. – causative Mar 5 at 1:30
  • "it's not based on anything logical. It's just a metaphysical claim." I wonder what you mean by that. Metaphysical claims already have no fact to support them, if you also remove logic what's left for them ? – armand Mar 5 at 2:52
  • If Dunne is addressing an issue of subjectivity re: time, why should he not appeal to something (purportedly) subjective about time? Or why should his reasoning not be subjective? – Kristian Berry Mar 5 at 3:08
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    @causative - It may be that he was not making a claim about relativity itself, but about reconciling relativity's block time with A-series style intuitions about time where there is an objective present "moving" through the 4D block (the moving spotlight theory of time), implying a second time dimension. But it'd help if heroyu could find the piece where Dunne's discussion can be found so that we could see the details. – Hypnosifl Mar 5 at 3:59
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    @causative - A believer in the A-theory of time could in principle accept that there is no physically preferred definition of simultaneity in relativity, but nevertheless believe in a kind of metaphysically preferred definition that would be invisible to all empirical experiments. The issue with closed timelike curves (leading to spacetimes that don't admit any global foliation into spacelike slices) would be more difficult for an A-theory advocate (assuming they are not ruled out by quantum gravity), but I suspect Dunne wouldn't have been aware of this. – Hypnosifl Mar 6 at 20:21
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I'm not sure if Dunnes' claim had a more logical ground, but from modern science like GR, spacetime should be better understood not as some real ontological absolute existence or substance like a container or a stage, but as a kind of base manifold illusion perceived from external quotient relation between mass and its affine connection fields. There was a fierce historical debate between space relationalism (Leibniz et al) and absolutism (Newton, et al) starting from the Bucket Argument to later Einstein's Hole Argument. So metaphysically, it's very possible space and time are both mere illusory relations between some other truly existed substances based on modern fiber bundle field theories, thus it's further totally possible there're more levels or dimensions about the commonly perceived "1-d time experience".

Also intuitively, we all have our own progressing pace of our own agendar in addition to a "universal" physical time as classically stated by Aristotle's "immanent unfolding entelechy" to visualize the higher metaphysical level of time which ultimately reflects our own perceived physical time as entelechy's shadow according to the synchronization of various laws. In fact I feel Dunne's claim is very similar to Aristotle's entelechy, which Leibniz later borrowed and called monadic activity/time. So in summary Dunne's claim makes sense on both scientific and metaphysical speculation ground...

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I seem to recognise that quote, it is from either Wikipedia or my web site, I wrote both.

Dunne's argument was that, in a four-dimensional block spacetime, such as Minkowski space, there was no unique moment of "now". On any given timeline, any "now" would have to be chosen arbitrarily. But clocks tick away steadily and we experience time as moving, the "now" moment travels along the timeline at the clock's steady pace. But how can one establish that the pace is steady, that clocks run true? (She had no clue and gave him a flea in his ear).

At the age of nine he had been convalescing and had challenged his nurse about this; did Time comprise the waystations of yesterday, today and tomorrow, or was it the travelling between these waystations?

He eventually concluded that one cannot use a thing to measure itself, one needs a ruler. So he could not use his timeline to measure the rate of passage of time, he needed a different ruler. His argument was that this ruler had to be a deeper level, another dimension, of Time.

This second time dimension was indeed subjective, as some comments have suggested. But Dunne regarded it as essentially real, and this led to the idea that consciousness existed in this second Time dimension, rather than the base physical Time of the brain.

One cannot say that his logic had any more basis than that. It promptly led him to the problem of measuring the passage of time in the second dimension, resolved in the same vein by yet further dimensions of time and consciousness, and so on into an infinite regress. He justified this solution with reference to a similar regress of time which (I think) McTaggart had been wrestling with.

But Dunne was in no way an academic philosopher and his relentless explanations and justifications, though claiming clarity, became notorious for their obscurity.

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As Kant also said, if we attributed succession to time itself, we would have to suppose another time in which the first would pass. But note that Dunne is represented as addressing the block time view. On this view, each 3d mapping of things in space is a facet of a 4d structure (spacetime). Like slides for a diorama. This leaves (arguably!) two options for the subjective perception of time passing: either we are rotating around the 4d diorama, or it is rotating "in front of" us. Either way, there's rotation. Since we eliminated the first dimension of time from the equation by uniting it with space as spacetime, nothing is left but to expand our notion of spacetime to at least five dimensions. I can't say that the fifth would be "another time dimension" as we don't really have space and time separated as concepts like that, here. But at least it should be timelike to the required extent... QED

But let the 5d structure be a block. Then to perceive it changing, we would have to have another dioramic rotation process, and so on and on... I imagine this is what Dunne was thinking along the lines of, though I haven't read his book(s) and am going off vague memories of a synopsis plus the above quote.

For reasons of unbroken symmetry, one might assert that either there is a reason space has more dimensions than time, or therefore (sans said reason) they must really have the same number of dimensions. Now if there's really just spacetime as such, the issue of symmetry is different as we have a four-dimensional thing just as is, though.

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Is (was) Dunne a mathematical physicist? If not, then his assertion is meaningless.

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  • There is a place for philosophy about time. See McTaggart's analysis, which is referenced by physicists (he was an idealist metaphysician). Answers should contain references to literature, not just be snide remarks. – CriglCragl Mar 5 at 19:04
  • @CriglCragl, I was not being snide. two-dimensional time has a specific, though arcane, meaning in physics, and I can't see any connection between that and what Dunne's assertion seems to mean. – niels nielsen Mar 5 at 19:16
  • @nielsnielsen Dunne's second time dimension was not part of the physical world, it was a mental or spiritual level of time. However he would have denied that it was mere untestable metaphysics. – Guy Inchbald Mar 6 at 19:26

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