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About davidm

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  1. davidm added a post in a topic Benefits of Relativity   

    Why should accurate theoretical constructs entail shorter lines at the supermarket? 
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  2. davidm added a post in a topic Benefits of Relativity   

    TGL is still here! Last time I looked it was a page that could not be accessed.
    Maybe it's time for a revival? 
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  3. davidm added a post in a topic "Does Fascism lurk around the corner for the US?"   

    Twitter closed DCD's account??
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  4. davidm added a post in a topic Dialogues on Art   

    bump to try to delete attachment
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  5. davidm added a post in a topic E-mail to Petkov   

    Here is my initial response to Prof. Petkov’s response to me, with more detail to be added later as I find more time. 
    I want to emphasize first to him that I understand perfectly his 4D world. On reflection, however, I do think that my thought experiment was poorly mooted; so I will clarify it momentarily.
    Just so that he and I are (I hope) on the same page:
    The 4D word exemplifies eternalism — the idea that the past, present, and future all exist. 
    The 3D world exemplifies presentism — the idea that only NOW exists; that the past once existed but no longer does, and that the future does not yet exist, but will “come into” existence, as time “passes.”
    I fully agree with him that science —  the theory of relativity — rules out presentism and establishes eternalism as the correct ontology of the world.
    I think that our dispute over his statement that all moments in time are given “at once” is mainly a semantic quibble, and does not carry great weight. At least I hope and expect so.
    I can only reiterate that to say that all of time is given “at once” seems to me to be a mistake on par with saying that all locations in space exist “here.” It’s true that all “heres” exist but they obviously are not all in the same location. The ontological Minkowski spacetime that he defends clearly gives each spacetime event unique 4D coordinates. It’s not that all of time exists “at once” but rather that all of past, present and future actually exist. If we agree on that point (as we do), then I think we can dispense with this quibble over “at once.” This is why I, as do many philosophers of time who are eternalists, prefer to say that all moments of time are “ontologically on a par” to avoid the misleading idea that all moments of time exist “now.” “Now,” like “here” (and like actuality according to David Lewis) is an indexical. Presentism holds there is only one indexical “now,” shared by all observers; eternalism holds that all indexical nows past, present, and future, actually exist. The theory of relativity proves that this is the case; the very idea of relativity of simultaneity is literally impossible in a 3D world.
    Professor Petkov dismisses my thought experiment because there can be no existent past, present, and future history of the world in 3D and of course he is right. If some observer standing outside space and time compared a 3D world and a 4D word at the end of time, he would see the entirety of the history of the world in 4D, and literally nothing at all in the 3D version, since the past would have gone out of existence in 3D. So my thought experiment is poorly presented. 
    But it can be salvaged. I ask the professor to envisage, in 3D world, a perfect record of the past from which a simulation of it can be generated, such that the simulation of the (nonexistent) 3D world is precisely isomorphic to the actual existence of the 4D world.
    My challenge stands: why should we say free will is possible in 3D but not in 4D? I understand that believers in free will think that an open future  (one that is not predetermined in advance) is necessary for free will to exist; but it is precisely this point that I dispute. I deny that an open future is needed to maintain free will, and I tried to explain why I think this is so in my initial email to the professor.
    I am inviting him to respond to this. If any others would like to respond, that would be nice, too. Though I realize the board, unfortunately, is in a bit of desuetude these days.
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  6. davidm added a post in a topic E-mail to Petkov   

    I do appreciate his response, but he's quite wrong about my alleged misunderstanding of the 4D world and his own response to my thought experiment entirely missed the point. I'll explain why this is so later. 
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  7. davidm added a post in a topic E-mail to Petkov   

    I have absolutely no idea why the bottom third of the response is in strike-through mode.  I certainly didn't put it there, but the software evidently did. In any case, it is still readable for any interested., 
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  8. davidm added a post in a topic E-mail to Petkov   

    Professor Petkov respods. Here is his response:
    Dear David (if I may - it is easier and, of course, if you decide, you could do the same), Thank you for reading my work and for taking the time to comment on the free will challenge. I am responding right away; otherwise, I would hardly manage to do it, because of approaching deadlines and my involvement in the 4th spacetime conference organization - <> (if interested you could still submit an abstract or you could attend just to participate in the informal discussions - see the program). Frankly, I wish your comments succeeded in eliminating the problem so I could finally sleep peacefully. Unfortunately, after reading them, I realized two things - (i) you did make a serious effort to eliminate the problem, and (ii) your conclusion "The “problem” is eliminated" was reached on the bases of several (not just one) crucial misunderstandings. For the reason mentioned above I will only and briefly comment on the three most serious misunderstandings (and will be able to return to free will only after the conference): 1. You wrote "I think it a bit odd to say, as you do, that all moments in time are given “at once” in a 4D world. This implies that all times happen at the same time..." You could have discovered yourself why you arrived at such absurdity - simply you used the everyday meaning of exist (= exist now); it is here (the second half of your first sentence) where it is evident that you do not have proper understanding of a 4D world - it is a 4D world namely because its fourth (time) dimension is given at once (like the three space dimensions), which means that all moments of time are indeed given at once since they form the fourth dimension. 2. You wrote "But according to Weyl, in a 4D world, something does move: consciousness somehow “climbs up” the world line, or world tube." This is a correct observation and your question of how the consciousness can move in the "frozen" block 4D world is obviously correct. Hermann Weyl was an extremely smart scientist and he new perfectly well that real problems in science (e.g., how to reconcile the fact that the real world is a block universe with another fact - that we are aware of ourselves and the world only and always at a single moment of time, which we call 'now') are not solved by using metaphors. I guess most probably his line of thought was the following - I have no idea what consciousness is, but as it is the consciousness that makes me aware of my own and the world's existence always at one singe moment of time, whereas all moments of time exist equally in the 4D world, it becomes obvious that the consciousness must move along my worldtube; if it is assumed that the consciousness exists along the entire worldtube, a contradiction is immediately reached - explained on pp. 114-15 of my book "From Illusions to Reality: Time, Spacetime and the Nature of Reality" (2013). We will probably never know why Weyl was not bothered by the exceedingly obvious fact that the consciousness moves in a "frozen" world; I guess Weyl (and all after him who thought deeply on that issue) did not see any other way to resolve the apparent contradiction between the two facts mentioned above; moreover, it certainly had been clear to him that consciousness is not matter... - in fact, if you are interested I can send you a link to the ebook version of my book mentioned above, where that issue is discussed in more detail near the end of the book. 3. You wrote "We put two worlds side by side. One world is 3D world and the other is a 4D world. Let us say that each of these worlds comprise a complete history from the Big Bang to a supposed Big Crunch." That is impossible - the assertion "each of these worlds comprise a complete history from the Big Bang to a supposed Big Crunch" is plain wrong: what you are saying is = one of the 2D sides (say the bottom side) of a cube is equivalent to the 3D cube. The accepted definition of a 3D world is everything that exists simultaneously at the present moment. The past does not exist (it consists of previous states of the 3D world) and the future does not exist either (it consists of all forthcoming states of the 3D world); again, careful with "exist"! So it is a contradiction in terms to say that a 3D world "comprise a complete history from the Big Bang to a supposed Big Crunch." [A model - a growing block universe - contains both past and present, but the future, like in the 3D world view, is OPEN.] A 3D and 4D worlds are fundamentally different - they are of different dimensionality. The distinction between them (between the two ontologies with two notions of existence) can be best visualized by the distinction between a 3D meter stick (what we all believe is what is real) in a 3D world and a 4D meter stick (worldtube) in a 4D world; see Figs. 5.6 and 5.7 in the PDF file given on the Free Will page (you gave the link). I will add a link to your comments (on your blog) on the Free Will page. If you like, you can post my brief answer above too; otherwise, I will post it on the Free Will page. The new blog mentioned on my site (as the name suggests) is about how to do physics right; so, at least at this time, I do not think the issue of free will should be discussed there; there are a lot of purely physical problems that need clarification and resolution. Best wishes, Vesselin Petkov 
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  9. davidm added a topic in Explore   

    E-mail to Petkov
    Here is an email I’m sending to Professor Vesselin Petkov on his essay, which I am trying to link to in a standard way, but appears the new software precludes this. Let me try to just copy-paste the link below:

    Dear Professor Petkov:
    Recently I read your essay on free will. I am not a scientist or a philosopher, but a layman who has read widely in both fields. I have also read all of your papers archived at the Phil Sci site.
    You hold that free will is not possible in a four-dimensional world. You do not specify what kind of free will you are talking about — compatibilist? Libertarian? Some other kind? — but I imagine you must mean that any kind of free will is impossible in Minkowski spacetime.
    I believe you are mistaken, and will present my case shortly, but first a few preliminaries.
    I think it a bit odd to say, as you do, that all moments in time are given “at once” in a 4D world. This implies that all times happen at the same  time, which is akin to saying that all different places in space are “here.” I think it better to say that in 4D world, spacetime events each have their own unique four coordinates. It’s not that all events in spacetime exist “at once,” but rather that all such events are ontologically on a par. Thus Socrates exists, but he exists in the distant past relative to what you and I call “now.” His now is as real as our now, but they are spatiotemporally separated.
    You take issue with the name “theory of relativity.” It is my understanding that Einstein himself regretted the name, and had wished it to be called the “theory of invariance.”
    You quote Weyl:
    “The objective world merely exists, it does not happen; as a whole it has no history. Only before the eye of the consciousness climbing up in the world line of my body, a section of this world ‘comes to life’ and moves past it as a spatial image engaged in temporal transformation.”
    Clearly, Weyl is trying to account for the illusion of passing time, which must be an illusion in a 4D world. But not only that, I would have to say that motion itself is illusory in such a world. But according to Weyl, in a 4D world, something does move: consciousness somehow “climbs up” the world line, or world tube. How does consciousness achieve this magical feat, in a block world where nothing else ever changes and everything that ever was, is, or will be, is simply given? This might be OK as a kind of metaphor to explain the illusion of passing time, but it seems completely inadequate as a scientific theory or even hypothesis: It is wholly non-explanatory. It seems to carve out a special place for consciousness, which may in fact be the case; but no explanation of what this special place is or how it works is given.
    In a similar vein, you write:
    “… the physical world is a four-dimensional block Universe and it is the consciousness which moves along the worldtube of our body (reading the information stored in our brain at different moments of time) and creates the illusion that there is an objective distinction between past, present and future (i.e., that time really flows).”
    Again, I find this deeply puzzling. It seems you are speaking metaphorically rather than scientifically or even philosophically. How does consciousness move like this? I have this impression of a flashlight slowly drifting along the world tube and from moment to moment “lighting up” previously stored conscious thoughts, but plainly if this is so, then the flashlight must be above and beyond the 4D world — or so it certainly seems to me. What I would say, rather, is that consciousness does not move along the world tube, and literally nothing is “climbing up” the world tube. Rather, consciousness is stored at every temporal part of the world tube, and each part experiences its own moment in time as being the indexical “now.” A temporal part of me is experiencing this date (March 19) as “now,” but all my other temporal parts at every spatiotemporal location between my boundary conditions (birth and death) is doing exactly the same thing.
    We do not really know what consciousness is. Some people still subscribe to metaphysical idealism rather than metaphysical naturalism: Naturalism holds that consciousness supervenes on matter, whereas the idealists hold that matter supervenes on consciousness. A proper solution to the so-called Hard Problem of Consciousness may be needed before we can explicate how consciousness precipitates the illusion of passing time in a 4D world.
    The main point I now wish to defend is that I do not agree that the 4D world precludes free will.
    In your essay, you imply that only in a 3D world would some kind of free will be possible, but not in a 4D world.
    Let’s conduct a thought experiment. We put two worlds side by side. One world is 3D world and the other is a 4D world. Let us say that each of these worlds comprise a complete history from the Big Bang to a supposed Big Crunch. Godlike we stand above these worlds at the Crunch and look back across the sweep of their respective histories. In so doing, let us imagine that each history is identical down to the minutest detail, and though we are Godlike, we do not know which world is 3D and which world is 4D.
    In this case, how would our hypothetical observer tell the difference between these two worlds? In the 3D world we suppose free will holds, but not in the 4D world. Yet, their histories are exactly the same. There is no way to tell which world has free will and which lacks it.
    The point is that regardless of whether we live in  3D or 4D world, there is only one history. (We will put aside ideas like quantum Many Worlds; such ideas are irrelevant for the purpose of this discussion since even if such worlds exist, we ourselves only experience one world and one history.) If there is only one history in either 3D or 4D, and the history is the same in our thought experiment, how can we say that one history encompasses free will and the other fails to do so?
    You say that in 4D world, the future history of the world is pre-determined, like a film in a can. This implies that the history of the world is necessary. But it's not. The history of the world, whether in 4D or 3D, is contingent. There are a limited number of necessary truths: triangles have three sides, no bachelor is married, etc. All other truths are contingent: they could have been, or could be, otherwise.
    Today I am typing this e-mail to you. Ten years from now, if I am still alive, I will likely be doing something very different: eating a burrito, say. In our thought experiment, let’s say I am eating a burrito ten years from now. I am eating a burrito both in the 3D and 4D version of reality. Why am I freely eating it in 3D but not in 4D? In fact, I am freely eating it in both!
    As today I type this freely, so in existent (under 4D) reality, ten years from how I am eating a burrito freely. (Or, more properly, in 4D, a temporal part of me is typing this now, and a different temporal part of me is eating a burrito ten years hence.) What’s the problem? As I see it, the problem is that under your version of free will, you implicitly smuggle in what I hold to be an illicit premise: that in order to have free will, we ought to be able to  CHANGE the future. This is simply wrong, regardless of whether the world is 3D or 4D. It cannot be emphasized strongly enough that whether the world is 3D or — as I believe you have proved — 4D, NO ONE CAN CHANGE THE PAST, PRESENT, OR FUTURE. But free will does not require that we be able to change anything!
    Rather, by our free acts, whether in 3D or 4D, we MAKE the past, present, and future, BE what it was, is and will be. 
    It does not matter if, under 4D, the world is “predetermined” like a film in a can. Each frame is one single way, true enough. Indeed, that is also the case in 3D, since in either case there is only a single unitary history. But WE OURSELVES determine the content of each frame, in both 3D and 4D. The ontology of the world does not affect free will once it is plainly understood that free will does not involve “changing” anything at all.
    Here is a different example. We know for sure that the past is fixed. This is true under both 3D and 4D. Now let’s suppose I have a time machine that can take me to the past. I enter it, and go to the past. Can I change the past? And, if I cannot, does that mean I lack free will?
    The answer is that I cannot change the past. But this does not mean I lack free will. Suppose I traveled to a point in the past before I was born. This means that at the time of my birth, a future temporal part of myself FREELY did in the past, even before I was born, exactly what he did there. He didn’t change the past. Rather, by his free acts, he helped make the past be, exactly what it was. And so it is with the present and the future. 
    It’s true I can’t change the future in 4D. But I can’t change it in 3D either! It doesn’t matter. I don’t need to change the past, present or future. I just need to make it be, within the limits of my power, what it actually is from moment to moment. Understood this way, free will, if it exists and isn’t barred for some other reason (we are all really wind-up robots, etc.), is indistinguishable under either 3D or 4D. If it’s valid in one it’s valid in the other. The ontology of the world has no bearing on free will. That’s why, in the thought experiment mooted above, the 3D and 4D worlds really are — when it comes to free will — indistinguishable! Thus I feel we should take the eliminativist stance when it comes to free will in 3D and 4D. The “problem” is eliminated.
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  10. davidm added a post in a topic "Does Fascism lurk around the corner for the US?"   

    Ah, I see that now. But there has been a fair amount of comment after the necromancy, so maybe we can keep this thing going.
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  11. davidm added a post in a topic "Does Fascism lurk around the corner for the US?"   

    I have missed, until now, an actual new thread, with multiple responses, at TGL.
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  12. davidm added a topic in Read   

    I wonder if Steven King or his publisher knows that King’s  novel “11-22-63” is online,  in full and for free. I can’t imagine that they would give permission for such a posting, for why would they? Hulu is soon streaming a mini-series based on the novel, and the trailers were captivating. It made me want to read excerpts of the novel, which I’d never read, and I looked for them online. Instead I found the whole damn thing. Perhaps King should travel back in time and prevent his novel from being illicitly posted in the first place. 
    Such time travel is the premise of “11-22-63,” in which a disaffected and recently divorced high school English teacher, Jake Epping, is charged by a friend with the task of traveling back in time to prevent the assassination of John F. Kennedy. The novel is a real page-turner — or page-clicker in this case. Long as it was, I seemed to have clicked through it no time and read it in full. Sorry, Mr. King,  no royalty from me.
    It’s a great yarn, with interlocking subplots and enough twists and turns to make the reader dizzy. Jake’s mission to the past isn’t made any easier when he falls in love with a beautiful librarian after arriving in Texas.
    Can Jake Epping change the past? Can he prevent JFK’s assassination?
    King comes up with what is, so far as a I know, a novel twist on the old time travel theme: the past does not want to be changed, and it fights you every step of the way. 
    Here King is on to something, but he doesn’t take it the necessary step further: It’s not just that the past doesn’t want to be changed — it cannot be changed. It cannot be changed as a matter of logic. Hence Jake’s mission is doomed from the get-go. Nothing in the past can be changed; not even the tiniest detail of it. However, this  inconvenient fact, once recognized and acknowledged, would make for a pretty boring novel, and King is never boring.
    Is travel to the past possible at all? It might be. Nothing in logic forbids such travel, and it may even be physically possible. All that logic forbids is conjointly traveling to the past and also changing it. The very act of traveling to the past does not, as one might suppose, change the past; rather it makes the past be just what it was: a spacetime region with a time traveler from the future in it. The time traveler was always there. His presence did not change anything.
    In King’s novel, the protagonist finds a path to the past. I wonder if King knows that this has scientific warrant? Perhaps he does, but decided that introducing the concept of the Gödelian closed time-like curves would daunt the reader. In any case, I felt his failure to explicate his “rabbit hole” in terms of Gödel’s solutions to general relativity was a missed opportunity, for his “path” idea is just how past-directed time travel work, if possible at all. This is because all of us travel in spacetime jointly, not just space or time singly, and some such paths can indeed lead to past-directed spacetime locations.
    The novel’s flaw, from a philosophical perspective, is that early on King broaches a discussion of the Grandfather’s Paradox but offhandedly dismisses it: “Why would anyone want to do that?” a character asks, referring to the the possibility of someone going back in time and killing his own grandfather. What King fails to notice, though, or (as I think) chooses to ignore for the sake of a good yarn, is that all efforts to alter the past are thoroughly contaminated by the Grandfather’s Paradox, which is just a special case of a general logical principle.
    In the well-known paradox, a man goes back in time to kill his own grandfather before the time traveler’s father is born. If he succeeds, the time traveler will never be born. But if the time traveler is never born, he will never go back in time and kill grandfather. But if grandfather is not killed, the time traveler will be born after all. If he is born, he will go back in time and kill grandfather, and then … the problem is obvious.
    It is thus logically guaranteed that the time traveler will not kill grandfather, no matter how hard he tries.
    But Jake Epping’s going back in time and saving JFK is obviated by the exact same logical structure of the Grandfather’s Paradox. Suppose Jake goes back in time and prevents JFK’s assassination. In that case, in the future, Jake will not go back in time to save Kennedy, because Kennedy was never killed and so Jake has no reason to go back and save him. But if Jake doesn’t go back in time, Kennedy will be killed. If JFK is killed, Jake will go back in time to save him. But if he saves him … etc.  It’s the Grandfather’s Paradox all over again, and it can’t be avoided.
    The larger philosophical point is that time travel to the past is no different from time travel to the future — it’s just more peculiar. Just as we cannot change the past, nor we can change the present or the future. Rather, by our acts, we make the past, present and future be what they were, are, and will be. We never actually change anything.
    When Jake Epping was born (in 1975, in the novel) his future self had already done, what he had done, in 1963. Those things included failing to prevent JFK's assassination, given that when Jake was born, JFK had in fact been killed 12 years earlier. Jake’s mission is logically futile even before he undertakes it. The poor man could have refused his friend’s request on grounds of pure logic and saved himself a lot of time (five years) and trouble (he gets into a lot of it). All he had to do was crack a logic textbook! See how useful philosophy can be, after all?
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  13. davidm added a post in a topic 2016 NFL Super Bowl thread   

    Carolina 36, Denver 17
    With the aid of a service dog, a gimpy and half-blind Peyton Manning manages to throw two TDs, one of which is caught by his dog. But it's not enough to win.
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  14. davidm added a post in a topic Yo! Star Wars!   

    Scotty and I need to write a sci-fi space opera.
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  15. davidm added a post in a topic FAO Nullifidian   

    Ty, Null. *yo*
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