On reviewing whathas been going on, itseems ot me that the essays and postings on the various threads in this forum on the Nature of Tme have one marked divergence: that between solidly scientifically based approaches, and others that are more philosophically based. I have been considering what one might try to say that links the two to some degree, with the following result:
The nature of time is crucial to human life, and indeed it is the flow of time that enables us to exist as humans: to think and plan, to experience things and to act, to love and to feel. If time did not genuinely flow in our minds, none of this would be possible: we would not be able to be fully human. Time is also crucial to the physical sciences, but in a complicated way: macro-physics and chemistry and all the subjects that depend on them such as astrophysics, geology, molecular biology, neuroscience, evolutionary theory are also formulated in a way that takes the flow of time for granted. However fundamental physics as conventionally formulated does not, and in particular quantum gravity and quantum cosmology enthusiasts pursue the idea that time itself, or at least the flow of time, is an illusion, as is made clear in various fqxi essays.
So a key issue that arises is, how do these views (the human and the fundamental physics one) relate to each other, given the fact that the macro world arises out of the micro world: microphysics underlies macrophysics, chemistry and biology, including our minds. I suggest there are essentially three different viewpoints possible, and each can be seen in essays and postings in this forum.
Viewpoint 1: First, there are the Illusionists: those who claim the microphysics picture is the indubitable correct picture, and as microphysics underlies the macro world, that picture must be the correct one at the macro scale too, whatever the appearances may be. So the Block Universe (BU) picture is the correct one at both the micro and macro scales: it applies to fundamental physics, astronomy, geology, biology, and human beings, including the internal functioning of the human mind. The appearance of the flow of time is always an illusion, including in daily life.
Viewpoint 2: Second, there are the Emergentists: those who recognise the validity of both the flow of time at the macro scale, and the claims of the quantum gravity workers that there is no flow of time at the micro scale. In that case, macro-scale phenomena in which time flows must somehow emerge out of the micro physics in which there is no flow of time. Time has a completely different nature at the macro and micro scales. The BU picture is true at the micro scale, and the Emerging Block Universe (EBU) picture is valid at the macro scale. Time is not an illusion at the macro scale, though it is at the micro scale.
Viewpoint 3: Third, there are the Realists: those who claim that the flow of time is real at both micro and macro scales, and there is some problem with the way the microphysics is presently formulated. When the true micro physics description has been found, it will be agreed that time flows at both the micro and macro scales. The EBU picture is the correct description at both micro and macro scales.
Comment on Viewpoint 1: The first option (the Illusionist one) is highly problematic because if the human mind is based in physics of this character, where the present time has no significant existence relative to any other time in the physical structure of the world in general and in the brain in particular; it does not then seem possible to derive a plausible physically based view of how the mind works that gives time an apparent reality in accord with our daily experience. The future is already determined and immutable, as expressed so clearly in the BU picture: if the mind can do anything active at all, which I doubt it can on this view, than all it can do is experience what is predetermined as expressed by the BU. It follows that all the essays posted here on this forum were determined before any of us were born. This is absurd. So I cannot concur with Viewpoint 1, because it seems that it simply does not take seriously our daily experience of how time works.
Furthermore, as has been emphasized for example by Anton Zeilinger, if Viewpoint 1 were the case then the whole scientific enterprise is undermined, because the process of first forming hypotheses and then testing them at a later time demands a meaningful experience of the flow of time in our minds, and hence in the physics underlying our minds. How can we believe that Einstein did not develop the theory of relativity by a process of reasoning that took place in time as he wrestled with the conceptual problems involved, but rather that the theoretical answer he arrived at was predetermined before he was born? It does not make sense. The very existence of science depends on Viewpoint 1 not being true.
And should you despite all these problems, on the basis of Viewpoint 1 succeed in somehow deriving a view of how the mind works in a meaningful sense that gets round all these objections, then I would claim that you have in fact arrived at Viewpoint 2 rather than Viewpoint 1, because it is Viewpoint 2 that acknowledges the apparent reality of the flow of time at the macro level, where the future is still malleable but the past is not, with the present essentially different from all other times.
Comment on Viewpoint 2: The second option (the Emergentist one) would be fine if it could work, but I cannot see how this conjuring trick will be successfully carried out, given the completely different views of time implied at the two levels. I can't see how there can be any kind of coarse-graining process that could successfully link the micro to the macro description, so there is a BU at the micro scale with an EBU emerging at the macro scale. Nevertheless this in essence is what a number of people propose (though not expressed in this way).
If truly shown to work, that would be a major achievement that would take both human life and the underlying physical theory seriously. It is certainly worth trying very hard to see if it can succeed, but I am very sceptical.
Comment on Viewpoint 3: The third option (the Realist one) is what my essay proposes, taking seriously the flow of time at both the macro and the micro level. It takes the view that quantum cosmologists who propose time is an illusion are not taking seriously the quantum measurement issue, in whatever way that issue is understood. No definite result can emerge from quantum theory unless an effective measurement process (as described in standard textbooks) takes place; but that is what is omitted or sidestepped from their considerations. When the time-based and irreversible nature of this aspect of quantum theory is taken fully into account, the macro and micro theories will both be best described by an EBU; and the flow of time in daily life will be satisfactorily incorporated into the theory.
If the third view can be vindicated, one can attain an adequate view of humanity without abandoning science. And indeed we should not abandon science, as it is an extraordinarily successful way of discovering important aspects of the nature of the universe in which we live. Indeed that is why the fqxi project is based in science rather than philosophy alone, and any submission of a useful proposal for handling the issue of time needs a solid scientific base as well as any philosophical remarks one my see as appropriate.
