In this article we expose and refute some of Phillip Dennis’s mistakes in physics in his latest attempt to overthrow the conventionality thesis of relativity. Recall that the conventionality thesis is the position that the one-way speed of light is not a property of nature, but a stipulated convention by which a given observer judges whether two clocks separated by some distance are synchronized. I showed in my first refutation of Dennis that he had arbitrarily assumed the ESC convention in his attempt to establish the ESC convention over ASC (Lisle 2024). But this is the fallacy of begging the question. I also showed in this same paper that the conventionality thesis follows logically from the relativity of simultaneity (Lisle 2024).
In his second attempt to establish the necessity of using ESC, Dennis made exactly the same mistakes that he made in his first attempt.[1] Namely, he interpreted the results of two observations as being consistent with ESC, while failing to recognize that they were also consistent with ASC. In science we call this the error of confirmation bias. In reality, ESC and ASC must always make the same observational predictions since they are merely two different coordinate systems for expressing the same underlying reality. But Dennis made some additional errors in physics that we will address here.
The Conventionality Thesis in the Physics of Einstein
Dennis claims, “Lisle at one-point claims that conventionalism is ‘the physics of Einstein,’ that is, special relativity. This is an assertion without proof . . .” Dennis is mistaken in three ways. First, I did supply the proof. In my first refutation of Dennis, I showed that the conventionality of simultaneity follows logically from the relativity of simultaneity (Lisle 2024). This was the entire point of the thought experiment with Michael and Sarah found just before the conclusion. Second, Einstein himself indicated that his theory was predicated upon the conventionality of simultaneity. He directly stated in his book on the subject that the one-way speed of light “is in reality neither a supposition nor a hypothesis about the physical nature of light, but a stipulation which I can make of my own freewill in order to arrive at a definition of simultaneity” [emphasis in original] (Einstein 1916). Was Einstein wrong about his own theory? Dennis seems to think so. But he just cannot offer a logical argument for his position. Finally, the physics of Einstein is not limited to special relativity, but also includes the general theory of relativity which includes the effects of gravity.
Dennis continues, “If philosophers take positions with respect to conventionalism . . . then there is broad consensus that Lisle’s assertion is false.” Two problems are apparent. First, there is “broad consensus” among scientists that the universe is billions of years old. But that doesn’t make it so. Dennis is resorting to the fallacy of the appeal to the majority. Second, he is wrong. In my reading of the literature, a majority of physicists and philosophers are in favor of the conventionality thesis. Dennis cites John Norton who is an exception. But that has no bearing on the truth of the issue. That would be the fallacy of the appeal to authority.
Dennis then states, “Readers can easily search the literature to find the debate on the two points of view.” That is certainly true. However, it is apparent that Dennis hasn’t bothered to read such literature because he repeats mistakes that have been refuted in that very literature – some of them over one hundred years ago! Recall that Dennis attempted to use slow-clock transport as an argument against the conventionality thesis – which was refuted by Eddington back in 1923 as explained in part four of this series.
Dennis continues, “If the two views are equivalent according to Lisle, it certainly is remarkable that there is a continuing debate.” First, this is a strawman fallacy. The conventionality thesis and the non-conventionality thesis are not equivalent! I would never claim that they are. Second, there is “continuing debate” about whether Jesus really rose from the dead. The fact that some people still doubt the Resurrection doesn’t mean that it isn’t absolutely certain. A person’s inability to understand an argument or unwillingness to accept its conclusion doesn’t mean that the argument isn’t conclusive and sound. I have made an argument for the conventionality thesis that Dennis has been unable to refute. So he simply points out that some other people are unpersuaded. But how is that remotely relevant?
General Relativity
Dennis claims, “Another key point is that the conventionality thesis is only valid within the context of the empty universe of special relativity. For our universe filled with gravitational bodies the argument fails.” This is demonstrably false. Simultaneity remains both relative and conventional in a non-Minkowski metric. In fact, I have published on the advantages of using a Gullstrand-Painlevé metric instead of the standard Schwarzschild metric to understand the behavior of black holes (Hamilton & Lisle 2008). The difference between the two coordinate systems involves a change in the stipulated one-way speed of light and hence the definition of simultaneity.[2] So I already refuted Dennis’s claim twenty-two years ago. But he simply isn’t familiar with the literature.
Notice that Dennis admitted in his above statement that the conventionality thesis is valid within the context of special relativity. Yet in his previous paper (and in this one) he has attempted to argue from the Minkowski metric that the conventionality thesis is not valid. But the Minkowski metric is the metric of special relativity. In other words, Dennis’s statement here is a tacit admission that his previous paper was in fact wrong. So why did Dennis include all the ad hominem fallacies in his latest response regarding my supposed “limited knowledge” of the subject when he apparently now agrees with me that his previous attempt to overthrow the conventionality thesis was wrong? Why didn’t he simply admit, “Yes, I was wrong in my previous paper to claim that the conventionality thesis is incompatible with special relativity, and I thank you, Dr. Lisle, for your response. However, I believe that the thesis is incompatible with general relativity for the following reasons. . .”? I would have been happy to consider his new claim and interact with any new arguments he proposed. But that isn’t what happened.
In fact, he made claims in his latest response that conventionality can be refuted within special relativity, having just admitted in the same response that “the conventionality thesis is only valid within the context of the empty universe of special relativity.” Which is it?
Notice also that Dennis made no actual argument from physics that the conventionality thesis is incompatible with general relativity. Instead, he simply cited someone else who apparently believes the same thing. But this is simply the fallacy of the appeal to authority.
Dennis states, “We will say more later, but cosmological solutions in GR do comport with presentism, as evidenced in the Friedmann-Lemaître-Robertson-Walker (FLRW) solutions which reinstated a global present equal to the cosmic time or age of the universe.” First, the physics of Einstein is certainly not compatible with presentism at all (as demonstrated in the previous article), and that includes the FLRW metric. Second, there is very compelling observational evidence that the FLRW metric is wrong. I have published a technical paper on this subject (Lisle 2025). Third, the “cosmic time or age of the universe” parameter in the FLRW is 13.8 billion years – a number that I reject.
Finally, does the FLRW metric reinstate an absolute “global present” that invalidates the conventionality thesis? Not at all. I suspect that Dennis is thinking that the scale factor in the FLRW metric forces us to accept a “universal now” that is the only true simultaneity relation. But this is false. It is convenient to use a reference frame in which the expansion of space occurs at the same rate in all locations at a given time coordinate in performing our computations. But this is not a logical necessity. We are free to use the reference frame of anything in the universe and use either ESC or ASC coordinates for that object – such as a neutrino that is traveling at nearly the speed of light relative to us. In fact, Dennis unwittingly admits this when he refers to “a global preferred reference frame given by the Hubble flow” (underline added). Yes, the choice to use the Hubble flow as the reference frame (and ESC) is a preference – not a requirement of general relativity. That’s the point. Likewise, the choice to use ESC or ASC coordinates is a preference. The relevant argument that Dennis has not addressed in any depth is which the Bible uses.
Dennis falsely claims, “Lisle bases his repudiation of presentism via elevating special relativity over general relativity.” What is Dennis’s evidence of this claim? The fact that I explained the conventionality thesis in the context of special relativity does not mean that I don’t accept general relativistic solutions for the universe. Obviously, I do. This is directly taught in chapters 15 and 16 of The Physics of Einstein (Lisle 2018). Why does Dennis keep misrepresenting my position? In fact, until recently, I believed that the FLRW metric was the correct metric to describe the universe. And that, of course, is a general relativistic metric.[3]
Misconceptions Repeated
In his original paper, Dennis considered the path of light reflecting off a mirror and returning to its source but allowing the light to have potentially different velocities on the outgoing and incoming trip. But he made several mistakes in reasoning, including thinking that a difference in the one-way speed of light would somehow affect spatial distances. I refuted that in Appendix A of my rebuttal (Lisle 2024). I also showed how you can empirically disprove Dennis’s claims (that synchrony conventions affect distances) in the second article of this series. But Dennis doubled down in his second paper and repeated this same mistake. First, we need to identify some fundamental mistakes in logic that Dennis made in this section.
Dennis claims, “Of course, there is only a single actual reflection event, and it is not conventional. That implies there must be a one-way speed of light that is a fact of nature.” However, the second sentence does not follow logically from the first and is actually false. The fact of a reflection event does not imply that the one-way speed of light is non-conventional, or non-relative. This should be obvious. It is even the case in non-relativistic physics.
Consider a fender-bender collision between two cars. Does the objective nature of the event mean that the speed of each car is objectively absolute? Of course not. The driver of car A sees car B moving east relative to him at 15 miles per hour, whereas the driver of car B sees himself as stationary, and car A moving west relative to him at 15 miles per hour. A person witnessing the event on the sidewalk might see car A moving west at 10 mph and car B moving east at 5 mph. An observer on Mars might see both cars moving at thousands of miles per hour. Events are objective; speeds are relative! The round-trip speed of light in vacuum is a peculiar exception to this principle due to the marvelous way God has designed spacetime. But the one-way speed of light, as Einstein stated, “is in reality neither a supposition nor a hypothesis about the physical nature of light, but a stipulation which I can make of my own freewill in order to arrive at a definition of simultaneity” [emphasis in original] (Einstein 1916). This follows inescapably from the relativity of simultaneity, as I demonstrated in my previous rebuttal of Dennis’s errors (Lisle 2024).
Dennis repeats a previous error stating, “There must be a one-way speed of light; the technology of the 1920s only implied they didn’t empirically know its value. Today we know its value empirically from experiments such as the Caltech femtosecond camera, among others.” Of course, Dennis’s error here was exposed and refuted in article three of this series. Dennis had mistakenly failed to consider the reflection of the light into the camera, rendering the experiment not a one-way test.
Consider a mirror located at a distance of R from a source of light at the origin O. Suppose the mirror is located on the x-axis. So x = R. A light beam is emitted from O and reflected off the mirror at R and arrives directly back at O at some time T. Would the time the light arrived at R affect the distance R? Of course not! Whether the reflection time occurs at 0, ½T, T, or anything in between will have no effect on the distance!
However, Dennis mistakenly thinks that the distance R depends on the chosen synchrony convention (ε). I already disproved that in my previous response to him. But he repeats this error stating, “This is an example of Lisle’s mistaken notion that the ASC coordinate change does not alter distance. The morphing cannot lay claim to maintaining the coordinate value of x (= R) as the physical distance and stay true to the geometry of Minkowski” [emphasis in original].
Indeed, Dennis mistakenly concludes, “In fact, as the morph evolves according to the change in epsilon from ½ to 1, the distance represented by the x coordinate changes from R to 0 continuously.” That statement is not only factually wrong, but Dennis’s reasoning for it makes no sense. He states, “In the final configuration on the right, the null interval OB is congruent to OA, that is, the final state has the light ray aligned with the x-axis. But for null rays the spacetime interval is zero. So, the x coordinate is now null and thus the distance along the x-axis is zero. It is no longer the original distance.” Dennis seems to think that x-coordinates are null (zero) because the spacetime interval of inward-directed light along the x-axis is null (zero). But that is absurd and is easy to refute. I will prove here that the x-coordinate (Δx) of the mirror remains R for any synchrony convention. Thus, I will show that spatial distances are unaffected by the choice of synchrony convention (ε).
The spacetime interval S (without assuming a synchrony convention in the x-axis) is:
S2 = Δx2 + Δy2 + Δz2 – c2Δt2 – (2ε – 1)2Δx2 + 2c(2ε – 1)ΔxΔt
Since the mirror lies directly on the x-axis, we have Δy = Δz = 0. Furthermore, for a beam of light, the spacetime interval is always zero (S = 0). So we have the following:
0 = Δx2 – c2Δt2 – (2ε – 1)2Δx2 + 2c(2ε – 1)ΔxΔt
Solving for Δt we find two solutions: one for outgoing and one for incoming light, respectively:
Δt = 2Δxε/c , 2Δx(1 – ε)/c
The total time (T) it takes light to complete both legs of the journey is therefore the sum of these two quantities:
T = 2Δxε/c + 2Δx(1 – ε)/c
Dennis conceded above that the distance to the mirror (Δx) is R when ε = ½ (ESC). (His mistake is claiming that R depends on the value of ε and goes to zero when ε goes to 1). Therefore, T = 2R/c. And since the total time of the journey is unaffected by our choice of ε, we can substitute this value of T into our synchrony-independent formula:
2R/c = 2Δxε/c + 2Δx(1 – ε)/c
Simplifying, we find:
R = Δx
Notice that ε does not appear in the final equation. Therefore, the distance to the mirror is necessarily R for all synchrony conventions (at an unchanged distance Δx from the origin). We have demonstrated that Dennis is wrong in his claim that R reduces to zero in the limit as ε approaches 1. We have shown from the synchrony-free spacetime interval that distances are unaffected by the one-way speed of light. It seems apparent that many of Dennis’s other mistakes stem from this fundamental and basic misunderstanding of the physics of relativity.
In the next article, we will continue to explore Dennis’s mistakes in physics, including a rare instance where Dennis actually gets something right. (Sort of.)
References
Dennis, P. 2024. A refutation of Lisle’s “refutation” of Dennis (2024). Answers Research Journal 17 (November): 709–738. https://answersresearchjournal.org/astrophysics/refutation-of-lisles-refutation-of-dennis-2024/.
Einstein, A. 1916. Relativity: The Special and General Theory, authorized translation by R.W. Lawson. New York: Crown Publishers Inc.
Hamilton, A. and J. Lisle. 2008. The river model of black holes, American Journal of Physics 76 (June 1): 519-532.
Lisle, J. 2018. The Physics of Einstein. Aledo, Texas: Biblical Science Institute.
Lisle, J. 2024. A refutation of Phillip Dennis’s claims regarding alleged inconsistencies in ASC. Biblical Science Institute (July 13). https://biblicalscienceinstitute.com/refuting-the-critics/a-refutation-of-phillip-denniss-claims-regarding-alleged-inconsistencies-in-asc/.
[1] Dennis 2024. All citations of Dennis are from this paper.
[2] Interestingly, Gullstrand-Painlevé coordinates set the one-way speed of light to be c in all directions relative to an observer falling into a black hole at the escape velocity at every point. It is essentially the black-hole version of ESC, and therefore Dennis should be championing my alternative coordinates here as the only “true” possibility since he advocates that ESC is the only possible system.
[3] Moreover, whatever metric ends up replacing the FLRW metric will also be a general relativistic solution.