Thread by @Jsincla43477730

In 2014, Bill Craig invited me and Robin Collins (he of the Cosmic Design Fine-Tuning argument) to be part of a debate team. The location was the Greer-Heard point-counterpoint forum at New Orleans Baptist Theological Seminary.

https://twitter.com/Jsincla43477730/status/1096789194528174080

Our opponents were one of the foremost cosmologists, Sean Carroll, one of the foremost philosophers of time, Tim Maudlin, and one of the foremost philosophers of religion Alex Rosenberg. This was quite something! I had been to Greer-Heard in 2007, when Bill was . . .

. . . 2nd man on the debate team that year. As I recall, it was on "The Future of Atheism", and the primaries were Alister McGrath & Daniel Dennett. That year I presented a paper for the Evangelical Philosophical Society on my topic of cosmological models and . . .

. . . their implications for cosmological arguments. That was shortly after hurricane Katrina had devastated New Orleans, and it hadn't recovered yet. So, first it was quite an honor to be invited to be on a Greer-Heard team. Secondly, . . .

. . . I had grown to love New Orleans and wanted to see it again (Anthony Davis, how could you! And yes, that was pass interference Saints fans!). What exactly was the significance of this event? It was fairly significant in my view. You want to have the best . . .

. . . conversation partners. What exactly was the intellectual state of respectability for cosmological arguments in 2014? When I began to get interested in this topic in the mid 1990s, the lay of the land was quite different. There was a strange symbiotic relationship . . .

. . . between young earth creationism and cosmologists. The YEC position (which I do not hold) was critical of the Big Bang, thinking it an atheist model of reality. This suited cosmologists operating within a rubric of "methodological naturalism" just fine. Beginnings . . .

. . . could be talked about openly without an annoying theological angle creeping into their field. Bill Craig was an outlier with his use of Big Bang cosmology to defend the 2nd premise of the Kalam Cosmological Argument ("The Universe began-to-exist"), along with . . .

. . . Hugh Ross at Reasons-to-Believe. As a physicist, I decided to pick up the thread and see if there was any "there there" to this. If you know me, you know this is part of my testimony in how I was led back to the Lord. But let's not get all syrupy. Let's stay . . .

. . . hard core intellectual. I began to research the development of singularity and 'incompleteness' theorems within cosmology, and their implications regarding constraining model classes to have a beginning. The rise of the internet, and the fact that my place of . . .

. . . employment allowed me free access to many of the critical journals helped make this a tractable task. Because there peace generally reigned (recall the symbiosis), cosmologists were easily reachable via email. Further, because cosmologists often enjoy teaching . . .

. . . they were willing to grant me use of their valuable time to answer questions. So a 'perfect storm' condition allowed cosmological research to be accessible and tractable to a properly trained person. Further, the nature of my own employment involves . . .

. . . sophisticated modeling of possible worlds, shall we say. As such it is routine for me to 'invade' another's field, learn what is relevant, and put it to use within modeling. Plus I would probably make a good science interviewer & writer if I had gone that route. . . .

. . . This research led me to contact Hugh Ross & Bill Craig and become involved with their ministries. Eventually Bill & I began to collaborate on articles and the rest is history.

My responsibilities for the 2014 debate were to prepare Bill, and . . .

. . . and to give my own talk on the 2nd day of the event. My choice of topic was quantum gravity, and what it seemed to have to say about a beginning for the universe. Just about that time, the 'symbiosis' had broken and some cosmologists were a bit concerned about the . . .

. . . interest of faith communities in their work (Note that there is a positive flip side to this: cosmologists seem to fill a role of secular priest as they have something meaningful to say about origin, hence creation, events. This allows them a audience to address . . .

. . . popular level books to. Nothing wrong with that.)

. . . Part of the reason for the breaking of the 'symbiosis' was my own involvement. I was probably the one that helped promote the Borde-Vilenkin-Guth incompleteness theorem to popular-level prominence. Alan Guth likely doesn't know that I am the bad guy in that affair. . . .

. . . The main article that Bill & I cooperated on was a Kalam defense in the "Blackwell Companion to Natural Theology" (now available on Kindle for a halfway reasonable price!)

By 2013 Bill was obtaining the attention of cosmologists and ended up in a debate series with . . .

. . . Lawrence Krauss in Australia. As I recall, the key moment (other that Krauss employing a Pavlovian dog whistle to rattle Dr. Craig) was the middle of the 2nd debate . . .

. . . where Dr. Krauss was willing to concede that the cumulative evidence within cosmology made it more likely than not, in his view, that the universe did have a transcendent beginning. He was willing to cop to Deism as a live intellectual possibility. . . .

. . . Flash forward to Greer-Heard in 2014. What should our preparation be? I knew that BVG (the incompleteness theorem) had grown a life of its own and this presented two problems for us. First, it produced a distortion of what our actual position was. Second, . . .

. . . it offered opponents an erroneous easy out in arguing that results from the General Theory of Relativity are meaningless because the real theory was going to be described by Quantum Gravity. . . .

. . . Now, our Blackwell article had covered this topic, but that was blown away by the natural desire for an easily explained sound-bite length 'silver bullet'. BVG started to serve this role for many people and I was devoted to set the record straight . . .

. . . (as, ironically, Dr. Alan Guth) on just exactly what BVG says. Then I wanted to ask the question, what might Quantum Gravity say about the issue of origins? That talk is online for those who want to see it. It was also reproduced in this book:

amazon.com/God-Cosmology-…

. . . The talk and the print article represent about a 7000 word summary of my research on the subject. The full topic led me to about 26000 words, which I selectively make available as appropriate. Quantum Gravity is an incomplete and speculative field, so there is . . .

. . . no such thing as getting to the end of the subject.

Regarding the debate, there were two more topic of interest that held our attention. First, Dr. Carroll had published a model; the Carroll-Chen model, a graphic of which is reproduced here with his permission:

. . . Is this model beginningless? The answer to me seems to be no (depending on what time really is), or 'it doesn't matter' (again depending on what time really is). This leads to the 2nd issue; if Dr. Maudlin is one of the foremost philosophers of time in the world . . .

. . . and the absolute heart of the issue (as the debate would come to show) as to Dr. Carroll's problem with Kalam regards time (and it's relation to causation), then wouldn't a discussion on the nature of time be the best way to spend our own time? Unfortunately that . . .

. . . isn't what transpired. Ironically, some of the things that Dr. Maudlin defends in print would have undercut Dr. Carroll's position! But that is an aside for another day. My general research in Quantum Gravity's claims regarding origins and the fact that the nature of time :

. . . was the heart of the issue, and the fact that Dr. Maudlin researches and writes on this very topic led me to investigate the topic of 'emergence' and how to understand it. A 'diachronic' understanding of emergence deals with a 'high curvature' primordial state . . .

. . . of the universe out of which 'emerges' a reality that is describable in terms of Einstein's General Theory of Relativity (GTR). A 'synchronic' understanding of emergence deals with how more primitive lower level descriptions of reality can result in . . .

. . . in a 'higher level' description such as GTR's 'spacetime'. Synchronic descriptions have nothing to do with beginnings. Theorists might also be discussing the lower level model as prescriptive, rather than descriptive (meaning what reality is really like) . . .

. . . which then makes the relevant issue not one of beginnings, but whether the 'emergence' to spacetime is possible; that is, is the model 'empirically coherent'? Lots of people get this diachronic/synchronic distinction wrong including some of the most accomplished folks! . .

. . . Another thing, it is probably useful to review quickly what Bill & I had previously said regarding model classes and beginnings which can be summarized neatly in this diagram from our Blackwell article:

. . . I am getting ahead of myself, as I am going to show the key parts of Dr. Carroll's argument via his own G-H presentation (again, with his permission). . . .

. . . But I want to get to something else first. Greer-Heard allows the participants to socialize with each other over the course of visits to famous New Orleans sites and eating some of that great food in the best restaurants. As such I got to know, a bit, the other team . . .

. . . This matters. I pretty much love and respect 'my enemies' (so to speak). Dr. Carroll is great. I respect him, and his work to the utmost. Still trying to get him to say that theism is at least an intellectually defensible position, even if he doesn't agree with it. Someday.

. . . I still intermittently converse with them. As I've already said, Dr. Maudlin is great. Some of his research may even help me in defending a position for another theistic argument, but that is not for today. His wife gave me the correct pronunciation . . .

. . . of Robert Geroch's name so I could stop betraying my uncultured origins. Dr. Rosenberg (got the spelling right that time!) told me some of his family history and some of his core beliefs that lead him to take the position that he does. . . .

. . . One of the core missions of Greer-Heard is to try to produce an environment of regard and respect that will surely make things within wider society (or even just within theist/atheist clashes) better. I believe it was accomplished that weekend. . . .

. . . So, what was Dr. Carroll's conclusion? Let's see the first two slides:

This is called a BLUF (or Bottom Line Up Front). The big reveal late in a story works best in the movies. Or a narrative with argument like I'm doing here. But in a presentation it's best technique. .

. . . Do I agree. No. Naturalism doesn't work. You know what works? Engineers building bridges. Not (with respect) cosmologists with speculative theories. The respect that the public holds for science as a truth finding activity comes from observation about how it . . .

. . . affects their lives. Engineers who build cell phones impact this view. Applied physics affects the reputation that science has. Ironically, as I've already said, cosmologists fill a 'priestly' function in secular society; not that of the literal bridge builder. . . .

. . . Does naturalism work as a philosophical system? Not a bit. Here are some sources on this: amazon.com/Naturalism-Cri…
amazon.com/Scientific-The…

. . . But that is something of a larger all encompassing debate, isn't it? I would say it is best to start with a bite sized topic and chew on that rather than exploring the totality of the topic. Let's just say that Dr. Carroll's contention is debatable; it's an assertion only:

. . . Dr. Carroll's slide on Kalam here is borderline ad-hominem. But we will let that pass. What motivates a 'not even false' call? Let's get into the meat:

Let's do a 'Bottom Line Up Front' ourselves. Dr. Carroll's case against Kalam is based on two factors:

1) Disputing causation
2) Proposed past eternal models

It will turn out that I have largely answered object (2). So let's focus on (1)

Interestingly, the heart of Dr. Carroll's case lies within the purview of philosophy; not physics! It seems to tug at Bertrand Russell's statement to Father Copleston in their famous debate: "philosophers have got going on cause".

. . . We're entangling multiple issues here. Descriptive vs. Prescriptive. Philosophy of Time. Humean critique of causation. Implications of a failure of the "Principle of Sufficient Reason" (which cross-polinates into another cosmological argument; the Liebnizian argument).

. . . Dr. Carroll's contention that physics deals with patterns seems fine; within a conservative view that seeks to make no metaphysical claims. These mathematical equations seem to describe what we see. Noting a lack of a 'cause' within those descriptions seems a category error

. . . Sure, I can describe the trajectory of a cannonball with a suitable equation as a pattern (sans cause), but is there really a claim that the cannon didn't 'cause' the ball's current movement? Or that the Artilleryman didn't fire the cannon? I don't think so. . .

. . . The answer can be yes if one drops the modest view of physics as description only and attempts a full-on Humean approach to causation. But now, if we stay away from universes popping into being (as Dr. Carroll indicates), we have picked a philosophy of time (tenseless) . .

. . . and are full on into a philosophical debate as to whether 'cause' is a philosophical primitive (non-reduceable; i.e. really exists) as opposed to supervening on other more primitive entities (i.e. causation doesn't really exist).

It turns out that on a . . .

. . . tenseless view of time laws-of-physics, forces, causation are all superfluous. They are unnecessary add-ons to the block universe. I have talked about this (and the tensed view of time at length in the link below.

https://twitter.com/Jsincla43477730/status/1035622271044538371

. . . Here I'm just going to summarize the implications. Carroll's view looks suspiciously like the view of David Lewis (he quotes Lewis in the full presentation). As such, I'm going to appeal to a critique of Lewis's view by philosopher Alexander Pruss. Book length, . . .

Here are two sources of his that bear on this topic: amazon.com/dp/B00Q2Z6X1C/…

amazon.com/Principle-Suff…

as well as his Blackwell article on the Leibnizian cosmological argument available for free here: alexanderpruss.com/papers/LCA.html

Notice this process is like the turtle trying to catch up with the hare. You'll get there eventually. Debate formats can't help but lead to this type of outcome. When the participants end up talking past each other, there isn't an ability to resolve these issues during the event.

. . . Keep in mind I am criticizing neither Dr. Craig nor Dr. Carroll. It's just the nature of timed debates, limited ability to respond, and what happens when the discussions by the participants are sufficiently divergent that you can't get resolution. . . . Now back to Pruss:

I'm now going to quote from myself; this is part of the larger article that didn't appear in the book. Yet it's the real issue!

"But, as I’ve said, the previous discussion presumed that laws of nature are based on causes that have real powers. Suppose, though, there are . . .

". . . no causes of this type and laws have no independent reality. Suppose laws are merely a-posteriori descriptions of how matter and energy have been seen to behave. Imagine an eternalist type of reality. A spacetime block simply subsists, populated throughout with . . .

". . . and energy arranged via no particular rhyme or reason. It seems to an embodied observer within such a world that things pop into and out of being (assuming an arrow of time). Occasionally something will appear to remain in existence and trace out some tortured . . .

"trajectory, or perhaps one straight as an arrow. This may not seem to be a particularly good candidate for a model of reality, but bear with me. Suppose we take our world (our spacetime) as a template. Imagine, now, we construct other worlds on a . . .

"‘recombination principle’ where our world is sliced and diced in every possible way. Every other way of rearranging things is exemplified in some other world. So, overall, there is a multiverse that would contain every possible variation on the apparent behavior of, . . ."

"for example, a pitched baseball. It turns out that such a multiverse can be convenient for solving certain pressing philosophical problems, such as understanding the philosophical problem of counterfactuals. Think of the movie It’s a Wonderful Life. When Clarence . . .

"the angel shows George Bailey the past he might have had, that’s a counterfactual. Now, on such a reality, there will be worlds that look like ours. But ‘gravity’ and ‘electromagnetism’ don’t really exist except as the coincident description of the way that the matter . . .

"appeared to behave in these worlds. There are other worlds that appear completely chaotic (no regularities that can captured as ‘laws’) and others where matter/energy will be arranged such that a law of ‘gravity’ can be written that has a different mathematical form . . .

"than the one that obtains in our world. This description of reality has been proposed by philosopher David Lewis, and goes under the name ‘Extreme Modal Realism’. The word ‘Extreme’ appears in the title to denote the exhaustive multiverse . . .

"Lewis proposes (not meant as a pejorative). ‘Modal’ applies to ‘modality’ which pertains to the why things are the way they are. As Pruss tells us in his Blackwell essay:
[Pruss speaking:]: "Alethic modality is a deeply puzzling phenomenon. Whence the difference . . .

. . . between a golden mountain and a square circle? Why is it necessary that 2+2=4, but merely contingent that horses exist? I could become a biologist, but I couldn’t ever be a number or a point in space. What makes that so?" [End Pruss]
Finally, ‘Realism’ means . . .

"Lewis is proposing this as a model of the way reality actually is.T here are other modal proposals where the other possible worlds are mere logical alternatives; they have no being. But in Lewis’s proposal they do. Now imagine my (above described) first two

possible worlds. [I'll have to tell you what those were: My first possible world looks exactly like our actual world, and turns out to run exactly like the common sense view of physics. There are no brute facts (although, for argument’s sake, they aren’t prohibited). . . .

. . . The world is governed by physical laws that take existing things and act on them over time to change them. In short, evolution is TRUE and governs all change. My second possible world looks exactly like the first, except that every contingent thing (my moments) . . .

are in fact brute. Nothing is how it is because of physical law (even if physical law exists).]
Pruss indicates: [Begin Pruss talking] "For Lewis, there is no difference between the two worlds you've described. According to Lewis: Causal facts supervene on counterfactual . .

facts. Counterfactual facts supervene on laws and the arrangement and properties of matter. Laws supervene on the arrangement and properties of matter. So as long as the arrangement and properties of matter are the same, so are the laws, the counterfactual facts and the . . .

causal facts.
Lewis will, indeed, deny the PSR.[1] [End Pruss talking]

[1] blogger.com/comment.g?blog…

[Begin me talking] "This looks like the causal reduction hypothesis. Thus there is no difference in worlds that look alike. For ‘laws’ supervene on the . . .

". . . arrangement of matter & energy. If we consider laws via a reductionist account, can we say science is achievable? Should EMR appeal to a scientist? The answer (still) seems to be no, for a reason similar to the earlier objection. Science requires that induction . . ."

". . . be possible; namely we should be able to predict future physical behavior based on what we’ve seen of the past. Now, in EMR, any possible past to a world can be combined with any possible future. . . ."

Says Pruss: [Begin Pruss talking:] "We can say that . . ."

". . . howsoever much regularity we might have observed in the world, if Lewis is right we have no reason to think it more likely than not that the regularity will continue. For corresponding to any one world that continues to be regular (i.e. governed by the inductively . . .

. . . observed natural laws) after this moment, there are infinitely many logically possible worlds that were regular but will no longer be so, and thus we have on balance no reason to think that we’re in a world that will continue to be regular. To the one world where . . .

. . . the apple dropped tomorrow will fall straight down, there correspond infinitely many different ones with the same past but in which tomorrow the dropped apple will take some tortuous path in an unexpected direction.] [1]

[1] Alexander Pruss, Actuality, Possibility and Worlds, kindle location 2600

[Me again] "Pruss suggests that induction can’t possibly work under EMR. Robert Koons agrees: [Begin Koons]
"There is another serious drawback to the junky cosmos hypothesis: if employed globally, it has the consequence that any form of induction is demonstrably . . .

. . . unreliable. If we embrace the junky cosmos hypothesis to explain away every appearance of orderedness in the universe, then we should assume that the simplicity and regularity of natural law is also an artifact of observer selection. Universes would be posited to . . .

. . . exist with every possible set of natural laws, however complex or inductively ill-behaved.
Now take any well-established scientific generalization. Among the universes that agree with all of our observations up to this point in time, the number that go on to . . .

. . . break this generalization is far greater than the number that continue to respect it. The objective probability that every generalization we have observed extends no farther than our observations is infinitely close to one. . . .

. . . Thus, relying on induction in such a universe is demonstrably futile.
In short, the junky cosmos hypothesis is both the most flagrant possible violation of Occam's razor and a death sentence to all other uses of that principle. . . .

. . . This hypothesis postulates an infinity of entities for which there is absolutely no positive evidence, simply in order to avoid the necessity of explaining the anthropic coincidences we have observed. This is the height of metaphysical irresponsibility, . . .

. . . far worse than the most extravagant speculations of medieval angelology. Moreover, it undermines all subsequent appeals to simplicity or economy of explanation. If the junky cosmos hypothesis is true, it is demonstrable that the simplest hypothesis of astronomy . . .

. . . or biology is no more likely to be true of our universe than the most complicated, Rube-Goldberg constructions. We would have absolutely no reason, for instance, . . .

. . . to believe that the Copernican hypothesis is more likely to be true than a fantastically complex version of Ptolemy's system, elaborated as far as necessary to save the astronomical phenomena.[1] [End Koons]

[1] Robert Koons: A New Look at the Cosmological Argument, arn.org/docs/koons/cos…

[Me talking:] "Now this seems right. It does seem that on a recombination principle, the number of wacky ways the world could proceed should be far larger than the ones where regularity appears to obtain. Thus we should not expect that, for example, the sun will come up . . .

. . . tomorrow morning. But Lewis has responded to this argument. He has shown there are, in fact, an infinite number of worlds where the behavior of the apple (in Pruss’s quote above) will continue to be regular. Now, infinity is a funny thing. The number of wacky . . .

. . . futures is infinite. The number of regular futures is infinite. It seems that the number of wacky futures should be far larger than the number of regular futures. But when you are dealing with infinity, you can have the counterintuitive result that the number of . . .

. . . members of the two collections is equal (if the cardinality of the infinities are the same). Another example: suppose you draw a line one centimeter long. How many points are there on the line? Infinity. Now draw a line two centimeters long. How many points are . . .

. . . on the line? There are an infinite number of points, yet the number of points on the two centimeter line is the same as the number in the one centimeter line. Another example: how many even . . .

. . . integers are there? There are an infinite number. How many total integers are there? There is the same number as there are even integers. Yet that doesn’t make sense. There should be twice as many even & odd integers as there are even integers! In fact, mathematicians, . .

. . . physicists and philosophers often aren’t sure how to compare infinities (of the same cardinality). Some philosophers (such as William Lane Craig) suggest that the type of bizarre behavior that is allowable in the mathematical realm can’t be exemplified in the . . .

. . . physical realm. Further, there are certain mathematical operations on infinity, for example, that are forbidden in Cantorian infinite set theory (thus in the mathematical world). But such operations (such as subtraction) can’t be prohibited if infinities are . . .

. . . exemplified in the concrete, real world. We may take this as another justification for the existence of instrumental models. Models are mathematical entities, and hence may have greater leeway in permitting the bizarre behavior of infinities, while the real world . . .

. . . may be more or less circumspect.

Now Pruss, in his writing, goes on to allow the best possible generous assumption that the number of futures that are regular are equal to the number that are irregular in Lewis’s multiverse. But this still results in a conclusion . . .

. . . that it is as likely as not that induction will not hold; you can’t be sure that the sun will come up tomorrow. Induction fails even on the most charitable view and hence science seems impossible on a Lewisian modality.
Since the lack of a cause implies lack . . .

. . . of an explanation with respect to kalam’s 1st premise, and that implies the impossibility of carrying out science if true, I think physicists should reject challenges to the first premise on that basis." [End me quoting my paper]

On a Humean account, (causation is not real; it's reducible to something else like the arrangement of particles on an eternal 4-D block), you still have to explain how it is the patterns we observe get there (there actually is a more serious problem; see the philosophy of . . .

. . . time thread I tweeted earlier, or find it in my thread-of-threads. I think the block universe leads directly to solopsism since you can't really know the patterns are out there; you can't observe other times or even other locations).

Lewis has the best response, but . . .

. . . even on that induction (hence science) is impossible. It should be rejected. REAL causation (which I would wager most physicists believe in) meaning REAL EVOLUTION (on the cosmic level) do exist. Isn't it ironic that, in the end, it's the theists who defend EVOLUTION?

That is, if you want to believe science is possible. I think physicists fit into that camp. So to claim that Kalam is 'not even false' on the basis of a Humean argument? I reject that. I think the Kalam defender has the upper hand. A belief I believe still holds on the . . .

. . . other view of time (tensed) where denying causation DOES imply universes just 'pop into being' (a claim Carroll does NOT make). By the way, you can't make an appeal that this claim applies 'in the universe' but not transcendent to it, because, by definition . .

. . . you are denying the Principle of Sufficient Reason (yes I know that facts and causes are not necessarily the same thing). It is precisely because the universe coming into being (or subsists for all eternity) FOR NO REASON that the claim is UNCONSTRAINED. Think about that.

I think I have answered the first challenge. Now the second: Dr. Carroll's laundry list of claims to past eternality:

About half of these have been responded to, directly, by me even before the debate. More importantly, they were responded to by Alexander Vilenkin. Others are theories of gravity, not models, that propose tweaking Einstein to avoid the three things a physicist doesn't want . . .

. . . to see in his models: Beginnings, Boundary Conditions, Fine-Tuning. You know why. Well, the experimental evidence backs Einstein. That's why GTR is so impressive. It doesn't back arbitrary tweaks to equations to avoid you know what. But how does Vilenkin see this?

You could make a list of 42, or 185 or what have you. But you really only have four, or five, or some small number. For most of these are just variants with classes. Classes of expansion behavior. If you address the class, you address all models within it. . . .

. . . This is how Vilenkin thinks. What does the history of cosmology since 1980 show? Claims to past eternality slowly go away under the pressure of further and further refined incompleteness theorems. Development hasn't stopped with BVG. Look at the work of Aron Wall . . .

. . . and his work on an incompleness theorem for a generalized 2nd law of thermodynamics. The fact that a physicist proposes an attempt at past eternality does not mean that it succeeds!

But suppose the idea of classification isn't used. Is a list of 185 . . .

. . . claims to past eternality foreboding? Why? Most of these claims are mutually exclusive. They serve as refutations of each other. Either only one is right, or they are all failures. This is great debate technique (a list), but doesn't withstand scrutiny.

Okay, what about the quantum eternity theorem?

Well, that is a claim from ordinary quantum mechanics, NOT quantum gravity. But even within ordinary quantum mechanics, open ended equations exist, but they are generally constrained by boundary conditions. For visualization only: Think of a guitar string vibrating.

. . . Sure, an equation exists that viewed without boundaries, appears to stretch spatially to infinity. But the equation doesn't exist by itself. It is constrained by boundaries to operate within spatial limits. The existence of mathematical entity by itself . . .

. . . doesn't imply eternality. But more importantly, if you do read my article in the book the conference produced (or watch the video), you'll see that quantum gravity tends to break down spacetime; especially time. An end to time as one looks backward along the timeline . . .

. . . (meaning time breaks down; ceases to have meaning) functions the same way in a Kalam argument as a singularity does in a GTR model! If you read the article, you'll see I end up endorsing what I call GTR+ models, which are quantum gravity perturbations to Einstein's . . .

. . . based, not arbitrarily, but on the particular quantum gravity theory. If you go full QG, you end up in the diachronic/synchronic issue. Again, a full breakdown of time (and maybe space) implies that the model is not describing a primordial phase of existence!

This is the problem that most people have with the Hawking-Hartle and Vilenkin tunneling-from-nothing models. Most don't understand so called 'Euclidean time' pseudo-eras and try to understand them as a primordial phase. Stephen Hawking's own messaging strategy . . .

. . . did little to resolve this issue. In fact, it isn't clear what he really believed about his model and the relationship of Euclidean and Lorentzian (normal) time. In my view, by the way, Both Hawking-Hartle and Vilenkin TFN serve as beautiful examples of creation-ex-nihilo

See my thread of threads for four ways to understand the HH and TFN models. See my thread of threads for my discussion of how this plays into Kalam's first premise.

Dr. Guth put in an appearance (by video) at the debate to our use of Alex Vilenkin regarding the BVG incompleteness theorem. When I saw that I thought 'my work here is done'. I've gotten Dr. Guth (noted for procrastination) to respond to me personally(tongue-on-cheek)!

Dr. Guth held up a sign indicating he doesn't think the BVG theorem indicates a beginning for the universe (although he left the possibility open). Very nice debate strategy! But what did he mean by this? Well, we now know that Dr. Guth defends a version of . . .

. . . an arrow of time reversal model.

Arrow of time reversal models are discussed in Thread-of-Threads here:

https://twitter.com/Jsincla43477730/status/1056573266318581767

The main issue is that they don't actually demonstrate past eternality. They demonstrate either incoherence, or they show disconnected bi-verses (or maybe multiverses in a more complicated setup):

So I was perfectly happy to see Dr. Guth pivot to an arrow of time reversal model.

Now, finally, last issue. What did I mean by my comments on the Aguirre-Gratton model (which Dr. Carroll separately uses as an example of a past eternal model). Here is the issue: just about that time, Dr. Vilenkin and Audrey Mithani (I think) published a paper claiming . . .

. . . that this unique model (constructed specifically to exploit a particular loophole in the Borde-Vilenkin-Guth theorem) does indeed feature a beginning. Now this ought to demonstrate my honesty and that I not an 'apologist' (in the bad sense of the world; something like . . .

. . . Shannon Sharpe is for Lebron James on the show 'Undisputed'). I disagreed with Vilenkin's claim. It seems to me his claim as to what a beginning is (in this instance only) was too broad. What he (Vilenkin) was claiming is that there is a boundary in Aguirre-Gratton which

. . . splits reality (a DeSitter hourglass figure if you want to try and visualize it) into two realities. In Aguirre Gratton, however, there are geodesics that reach arbitrarily close to this real physical entity, but never reach it as one looks to the past. There is a . . .

. . . 'measure zero' number of these worldlines that, formally, are past eternal. 'Measure zero' is something like a finite number divided by infinity. To avoid the Boltzmann brain problem in modern Former Eternal Inflation models (where the vacua decay faster than they produce

freak observers, (see my Thread of Threads for discussion of the Boltzmann brain issue), theorists like Leonard Susskind have pivoted away from Eternal Inflation (EI) models and such models feature a 'measure zero' set of worldlines TO THE FUTURE.

How do I take this? I agreed with Dr. Carroll on an issue over against Dr. Vilenkin. I'm not going to disagree with him all the time. In fact, I probably would agree with the vast majority of his contentions regarding cosmology; especially his excellent work on . . .

. . . the 2nd law of thermodynamics and the 'past hypothesis' (there was a past, and it had lower entropy than today. See my thread-of-threads for my discussion of Penrose Cyclic Cosmogony, as well as Andreas Albrecht's work regarding this topic. My paper on its . . .

. . . implications regarding the FTA (fine tuning argument) will appear in print this month (see my announcement from a few days ago). Someday I'm going to critique @seanmcarroll 's solution to the Boltzmann brain problem. It is not at all true that I uniformly . . .

. . . disagree with him, think I'm going to end up right in all disagreements, or will hide when I do agree with him on a topic related to Kalam or FTA.

So what is the significance of Aguirre-Gratton? Well, it appeared in the literature just after BVG was published that A-G was

regarded just as a proof-of-principle that a model could be constructed around one of its loopholes. Now, I have a 5000 word document that exhaustively talks about those loopholes. I'm not going to repeat it here! I take it as just that; not an attempt at a model to . . .

. . . describe reality per se. Just to advance the understanding of just what BVG says. I would also pipe in as a modeler (given my day job executing sophisticated physical models) that you usually don't want to take a model as completely literal.

For example, as Martin Bojowald (he of the Loop Quantum Gravity Theory) told me, the Hawking-Hartle and Vilenkin TFN models only have one degree of freedom! They hardly can be said to be complex enough to govern the whole world. Bojowald believes they are too simple . . .

. . . and that additional physics are needed to understand issues like 'bounces', reversals of arrow-of-time, incommensurate timelines, etc.

I believe that is probably true for claims of "measure zero sets". I don't claim that it is IMPOSSIBLE to envision a truly . . .

. . . beginningless model. It is merely EXTREMELY DIFFICULT.

ENUFF SAID

@threadreaderapp unroll