On Time, Aristotle, and Relativity
As I have noted many times over the years, I believe Aristotle’s metaphysics to be every bit as antiquated and outmoded as are his physics. I have expressed wonderment at the fact that everyone seems to have rejected his notions that the Earth is the center of the universe, that heavy things fall faster than light things, that the sky is composed of aetherial spheres, and a great many other things; and yet there are philosophers who ardently and doggedly remain attached to the ideas of hylomorphism, finitism, and– particularly– act and potency.
This latest notion has been a topic of discussion on Boxing Pythagoras very nearly since the start. One of my earliest articles was on William Lane Craig’s Theory of Time which is not explicitly Aristotelian but which is nonetheless predicated upon similar notions to act and potency. This has factored into my discussions on a range of other topics, including the Kalam Cosmological Argument, which explores the implications of the temporal finitude of the universe; the Grim Reaper Paradox, which purports to give good logical reasons to doubt the existence of actual infinities; Free Will and Determinism, regarding how to reconcile the notion of free-will with wholly extant Time; Infinity and Eternity, wherein I discuss how even a universe which does not extend infinitely into the past can be eternal; and most germane to our discussion today, Thomas Aquinas’ Five Ways, in which the eminent 13th-Century philosopher attempted to demonstrate the necessity of God’s existence explicitly through the Aristotelian notion of act and potency.
What are ‘Act’ and ‘Potency?’
While contemplating the nature of change– particularly in response to claims by Parmenides and Xeno of Elea that change is impossible– Aristotle began to develop a theory of time which accords quite well with our everyday, common sense experience of the world. On Aristotle’s view, there are things which currently exist– such things are actual or ‘real.’ Thus ‘act’ is a reference to this quality of being actual. These actual things exhibit ‘potency,’ or the potential to bear some other quality. So, to borrow an example from an expert on Aristotelian philosophy, Ed Feser, a green banana which currently exists is actual. This banana may yet become a yellow banana, but that yellow banana is not actual and only potential. 
Change, on Aristotle’s view, is thus the occurrence of a potentiality becoming actualized. When the banana ceases to be green and instead becomes yellow, the yellow banana is no longer potential, as it had been previously; but rather it is actual, as it had not been previously.
This seems perfectly straight forward. Things in the present are actual and real. The future holds only potentiality and is not actual— that is, not real. The present, actual green banana exists. The future, potential yellow banana does not exist. After all, if one were to throw the green banana into a fire rather than allowing it to ripen, the potential yellow banana would never come about. It is not the case that I am destroying both the green banana and the yellow banana that it may become. The yellow banana does not exist and therefore cannot be acted upon.
Time, on this view, is the manner by which we measure change. From an Aristotelian perspective, it is necessarily relational. When we say that it takes three days for a green banana to ripen and become a yellow banana, we thereby mean that there is some correlation in the ripening of the banana and in the rotation of the Earth. This correlation is the time which elapses.
Though perhaps a bit more verbose than the average person might be in describing the situation, this certainly comports well with the common experience of time and change. Indeed, it is quite difficult to see how such a position might be assailed, at first.
Newton’s Absolute Time
Aristotle’s work was picked up and continued by Arabic philosophers in the Middle Ages, particularly by Abu I-Walid Muhammad, commonly known in the West as Averroes. The work of Averroes was highly influential in the West, introducing Medieval Europe to the broad work of Aristotle for the first time in half a millennium and helping to supplant the Neo-Platonist views which had dominated the West since before the fall of the Roman Empire. It was through Averroes that Thomas Aquinas came to know the work of Aristotle and it was likewise through Aquinas that the Roman Catholic Church– and, indeed, most of Western Christendom– became entrenched in Aristotelian ideas.
By the 16th-Century, Aristotelian philosophy had become strongly ingrained into the fabric of Western thought; but the 1500s also were noteworthy for leading into a time of political, religious, and intellectual dissent. Thinkers in all walks of life were challenging the traditions and notions which had been held as nearly unassailable in previous generations. In addition to areas of theology and politics, this intellectual freedom spread to the exploration of Natural Philosophy– the branch of learning which would eventually morph into our modern understanding of the physical sciences.
While just about everyone has heard that thinkers like Copernicus, Galileo, Kepler, and others ushered in a revolution many people are under the mistaken belief that these men were chiefly opposed on theological grounds. In truth, these revolutionaries were far more controversial for bucking the trends of Aristotelian thought than for opposing the Church. Even Galileo, who is quite often used to fuel arguments about the compatibility of faith and science due to his run-in with the Inquisition, did more to upset the supporters of Aristotle than he did to upset supporters of Scripture. His use of the telescope to observe that Jupiter has moons and that comets cross the paths of several planetary orbits– things which are now so commonly known as to be taken for granted even by elementary school children– was considered to be infuriating, preposterous, and highly controversial, in his day.
Toward the end of the 17th Century, Isaac Newton continued on this trend. Among his many innovations was a view of Time which, in some ways, reversed the idea proposed by Aristotle. On the Aristotelian view, Change is more fundamental than Time. It is only by means of Change that Time even exists. However, Newton’s view was the opposite: Time is the fundamental notion, and Change is simply a description of differences in a physical state with respect to Time. This view was fundamental in his development of mathematical fluxions, which in turn led to his invention of the calculus.
Notably, Newton’s view of Time didn’t necessarily overturn Aristotle’s notions of act and potency. It’s fairly trivial to come up with notions of act and potency which are completely valid from this Newtonian perspective. However, by shifting the primacy to Time and away from Change, Newton’s Time offered up a new possibility. If Time is the fundamental thing then perhaps the future can be real and extant along with the present. Newton’s Time opened up the possibility that act and potency are epistemic descriptions of our knowledge of the world rather than the prescriptive governors of the world’s behavior.
By way of analogy, think of a pencil being drawn across a piece of paper. The tip of the pencil represents a being which exists and the line which appears on the page represents Time on the Aristotelian view. There is no Time until the tip of the pencil moves across the paper, generating it. The future doesn’t exist yet, and the pencil can potentially be moved anywhere else on the page.
Newton’s view without act and potency, on the other hand, might be envisaged as a bead on a solid wire which can only be pushed in one direction. Here, the bead is our extant being and the wire is Time. The past is represented by the wire behind the bead, while the future is the wire ahead of it. The future exists every bit as much as the past and present and the bead simply continues along it, rather than generating it like the pencil line.
Though certainly very interesting, this notion didn’t really catch on. Newton’s view of Time having primacy over Change began to be prevalent but its adherents still stuck to something akin to act and potency in their descriptions of it.
Einstein and Simultaneity
Nearly two and a half centuries after Newton, Albert Einstein published a paper which would completely overturn the way in which humanity had always thought about time. Though the paper was originally entitled “On the Electrodynamics of Moving Bodies,” the idea which it lays out has come to be known as the Special Theory of Relativity. It is now one of the most successful, well-tested, and empirically verified theories of modern physics; but in 1905, it was mind-bendingly controversial.
An earlier physicist named James Clerk Maxwell had developed equations describing the behavior of electromagnetic waves– that is to say, the behavior of light– which now bear his name, Maxwell’s equations. One of the surprising consequences of Maxwell’s equations is that the speed of light is constant regardless of whether or not the person measuring it is in motion.
Think of it like this: imagine you are standing on the side of the road with a police-issue radar gun. A car is moving towards you at 30 miles per hour and, unsurprisingly, the radar gun gives a reading that says the car is moving at 30 miles per hour. Now, let’s say that instead of simply standing still on the side of the road, you are also in a car which is moving at 20 miles per hour. Again, a car which is moving at 30 miles per hour drives towards you, but this time the radar gun gives a reading of 50 miles per hour. The other car seems to be approaching you more quickly. The radar reading has essentially added together the speeds of both vehicles. Similarly, if you were driving at 20 miles per hour and the other car was moving away from you in the same direction at 30 miles per hour, the radar gun would read 10 miles per hour, as if the other vehicle was moving more slowly. Its reading has essentially given the difference between the speeds of the two vehicles.
This is where things get strange. If we had a hypothetical super radar gun which could get a reading on, say, a single photon we could try this experiment again. The speed of light is exactly 299,792,458 meters per second– approximately 186,000 miles per second. Now, we start the experiment as before, standing still while a photon approaches us. The super radar gun reads 186,000 miles per second, just as we would expect. Now, we hand the super radar gun to Superman and he takes a measurement while flying directly towards the photon at 10,000 miles per second. We might expect that our super radar gun gives a higher reading of 196,000 just like the experiment with the cars. However, what we would find is that it still reads 186,000. If Superman speeds up to 30,000 miles per second or 50,000 or 100,000, the super radar gun still reads 186,000 every time. Similarly, if Superman chases after the photon with the radar gun, no matter his speed, the reading is always 186,000.
This was certainly strange, on its own merits, but Albert Einstein realized that its implications were even weirder.
Einstein asked a question which seemed simple, on its face. What does it mean for two events to occur simultaneously? The common-sense, obvious answer is that both things happen at the same time. Einstein’s innovation was in realizing that this answer is sorely lacking when one considers the strange phenomenon of lightspeed. The best way to explain why might be with a little thought experiment which Einstein proposed.
Imagine we have two people, Harry and Joe. Harry is standing next to a set of train tracks staring directly ahead at them. Joe is aboard the train, sitting exactly in the center of his car, and the car is about to pass Harry at a constant velocity. From Harry’s perspective, at the precise moment when Joe is directly in front of him, two bolts of lightning strike simultaneously, one at each end of Joe’s train car. Since both bolts of lightning hit the train at equal distances– half the length of the train car– away from Harry, the light from both strikes will take the same amount of time to get to him. During the time it takes for the light to travel, the train keeps moving on, and Joe along with it, so that Harry observes the light from the front strike hitting Joe slightly before the light from the back strike.
So far, nothing about this seems unusual.
However, let’s rethink the scenario from Joe’s perspective, now. Remember that the speed of light doesn’t change, even for an observer in motion. When Joe observes lightning strike one or the other end of the train car, the light from those strikes will each still have to travel half the distance of the train car to get to him. Since the speed of light is constant, it will take exactly the same amount of time for light from the front of the car to reach him as it will take for light from the back of the car. Thus, from Joe’s perspective, the lightning strikes the front of the train car before he and Harry are even aligned while the lightning which hits the back of the car doesn’t strike until after he has already passed by Harry.
These are the same three events: lightning striking the front of the car, lightning striking the back of the car, and the two people lining up with one another. From Harry’s view, the events all happen simultaneously. From Joe’s view, the front strike happens first, then the alignment, then the back strike.
At this point, it is tempting to ask, “Which one is correct? Harry or Joe?” However, the somewhat confusing answer is that they both are. What Einstein cleverly pointed out is that the inertial reference frame of the observer provides the basis for his observations of time and space. That is, the observation is necessarily relative to the observer. There is no absolute framework of space and time in which we all move equally. Rather, each inertial reference defines a relative framework of space and time.
Act and Potency in light of Relativity
So why is all of this important with regard to act and potency? Remember, again, that on the Aristotelian view a potentiality does not exist and that only actualities exist. So, a thing which may happen in the future is potential while things in the present are actual.
But how do we reconcile that view in light of Relativity?
From Harry’s point of view, all three things (front strike, back strike, alignment) were actual at the same time. All three were real at the same time. However, from Joe’s view, when the front strike became actualized both of the other events were still only potential. First the front strike is real, then the alignment, then the back strike.
Mathematicians and physicists quickly realized that this sort of behavior could be modeled using a four-dimensional system which we now call a Minkowski space, after Hermann Minkowski, the mathematician who pioneered the method in 1907. This imagines the universe as a four-dimensional geometric object using the familiar three dimensions of space with a fourth, perpendicular dimension describing time. Though it is difficult to imagine such a space in one’s head, the mathematics of it is actually fairly simple– if you can handle the Pythagorean Theorem, you can handle the basics of Special Relativity.
Soon after the introduction of the Minkowski space, philosophers began to note that this appeared strikingly similar to our earlier discussion from Newton, wherein Time was more fundamental than Change and the future was just as real as the present or past. The only difference was that, where Newton viewed Time as being absolute, we now understood it to be a Relative phenomenon. Suddenly, a notion which had seemed flighty to past generations was not only being treated seriously but seemed to do a better job of describing the world than the Aristotelian notion which had held sway for over 600 years.
Implications for the Concept of Change
Though these seeming implications and the massive success of Relativity Theory have been more than enough to convince a great many people that Time does not behave in the manner we once thought, there nonetheless remain some who reject the notion that the future is just as real as the present. William Lane Craig’s is one example whose thoughts on the subject have been a frequent topic on Boxing Pythagoras (see Parts 1, 2, 3, 4, 5, and 6). Thomist scholar and Aristotelian philosophy expert, Ed Feser, is another example. In 2017, Dr. Feser wrote an essay to be contributed into an anthology of work discussing Neo-Aristotelian philosophy and its application and relevance to modern physical science. In the essay, he raises several objections to the idea that Relativity does away with the notions of act and potency.
While setting the stage for his objections, Dr. Feser tries to characterize the issues which a Relativistic block universe pose for act and potency. He says:
The way that relativity is supposed to pose a challenge to that theory is not by showing that it is mistaken as an analysis of the preconditions of change and temporal passage, but by showing that there are no such things as change and temporal passage in the first place. 
By “change,” here, Dr. Feser does not necessarily mean the actualization of potentiality, but rather a somewhat weaker statement: “the gain or loss of an attribute, but also the persistence of that which gains or loses the attribute.” On this notion of change, it is not strictly correct to say that relativity is supposed to show that there is no such thing as change. Rather, the notion of change put forward here simply needs one extra qualifier: “…with respect to time.”
To illustrate the importance of that qualifier, imagine an elementary school ruler which is frozen in time. Now, it would be perfectly cogent and reasonable to discuss the manner in which the ruler changes– that is, gains or loses attributes while still persisting– over the course of its length. We might observe that at one end there is a hash mark labeled with a “0.” Farther down the length, there is no longer a zero mark, but a hash mark labeled “1,” and then farther down a “2,” and then a “3,” and so on. Even if the ruler is frozen in time, it is clear that it changes with respect to its length.
Changes of the sort Dr. Feser wishes to discuss are more properly termed “changes with respect to time” in physics. Remember that while the Aristotelian view gives primacy to Change and offers Time simply as a way to measure it, the modern Relativistic view gives primacy to Time. As such, it is perfectly cogent to discuss the manner in which an object which persists through successive moments of time gains or loses attributes across those moments.
It is only in the consideration of the universe as a whole that the notion of change breaks down. When considering the universe as a whole, we are looking at all points in space across all moments in time. We can’t say that it changes with respect to time because it already encapsulates the whole of time. The universe as a whole does not gain or lose attributes, on this view. It is only when we limit the scope of our consideration to entities within the universe with respect to some particular dimension of measure that change becomes at all meaningful– but it is still, thereby, meaningful.
This realization stands in direct opposition to Dr. Feser’s framing of the purported problems between Aristotelian act and potency and the implications of Relativity. It is not the case that Relativity denies that change occurs in the first place, as Dr. Feser states. Rather, it is the case that Relativity requires us to rethink the way in which we understand change– precisely challenging act and potency “as an analysis of the preconditions of change and temporal passage.”
Given this, Dr. Feser’s later discussion of what he terms “facile” appeals to Ockham’s razor are seen to be not quite so facile. While it is true that an account still needs to be made for the psychological experience of temporal passage, it is not true that we need to account for the appearance of change as our point of view does not entail the denial of change. Appealing to Ockham’s razor, in this regard, is no more facile than Copernicanism’s appeal to Ockham’s razor despite the fact that we do not have a psychological experience of constantly zooming around the Sun.
Neo-Tychonic and Neo-Aristotelian Parallels
After arguing against appeals to Ockham’s razor, Dr. Feser presents several attempts at reconciling the Aristotelian view with Relativity. Interestingly, the Copernican model offers even more parallels to this discussion so a bit more history would seem to be in order.
When Nicolaus Copernicus first put forward his idea that the Earth and the planets were in motion around the Sun, rather than the Sun and planets being in motion about the Earth as in the standard Aristotelian thought, it was noted that such geometric and mathematical descriptions were certainly useful but that this usefulness did not mean that they were accurate pictures of reality. As such, Copernicus’ method was considered to simply be a means of calculation while people still supposed that the Sun and planets were in motion about the Earth.
Similarly, the very first attempt at reconciling Relativity with Aristotelian thought which Dr. Feser lists is to consider the mathematics a useful fiction but to insist that it does not actually describe reality.
As Copernicus’ ideas began to be better supported by observation and data, another astronomer named Tycho Brahe took note, but objected on philosophical grounds. In Aristotelian thought, the Earth was far too heavy and sluggish to be able to move while the celestial bodies were composed of an aetherial substance which was quick and spritely. Still, Tycho Brahe could not deny that Copernicus’ method was seemingly as accurate as the previous Ptolemaic system while being significantly simpler in terms of calculation. As such, he developed a composite system in which the Earth, itself, was still and motionless while the Sun was in motion around it, but that all of the other planets were in motion around the Sun instead of the Earth. Rather than Aristotelian geocentrism or Copernican heliocentrism, the Tychonic system was geoheliocentrism. It was an attempt to bootstrap Aristotelian philosophy into a system which had controverted that ancient ideal.
In the same way, Dr. Feser’s second approach to reconciling Relativity with act and potency is to note Dr. William Lane Craig’s work on the subject (which, again, has been discussed previously on Boxing Pythagoras). Craig suggests that we might be able to notions like act and potency if we posit the existence of some particular inertial reference frame which is the ‘correct’ one while all other inertial reference frames are simply distortions of that correct one. Both Craig and Feser do acknowledge that this ‘correct’ frame would be undetectable but defend it by noting that detectability is not a prerequisite for a thing’s existence. The problem, however, is not just the detectability of this ‘correct’ frame but rather its indistinguishability. There is literally nothing which might distinguish the correct frame’s correctness from any other frame’s incorrectness. It isn’t simply that we would not be able to pick out the ‘correct’ frame in a lineup; rather, nothing about that frame can, even in principle, be set aside as denoting its correctness other than a completely arbitrary distinction. Just as had been the case with Tycho Brahe, this is simply an attempt to bootstrap Aristotelian philosophy into a system which has controverted that ancient ideal.
To this day, there still exist people who are so philosophically drawn to pre-Copernican ideals that they advocate for geocentrism even in a time when astronomic technology is so commonplace as to be utilized every single day by completely normal people. Robert Sungenis, for example, is a very vocal Catholic theologian and apologist who holds to what he a Neo-Tychonic view. Perhaps ironically, Sungenis appeals to Relativity to note that since motion is relative, it is perfectly reasonable to consider that the Earth is stationary while all other bodies are in motion relative to it. He then makes the rather unjustified jump that this is somehow the correct view while all others are incorrect, thus preserving both the ability to use predictive physics and his preconceived philosophy.
Again, we can find a parallel in Dr. Feser’s reconciliations of Aristotle and Einstein. Feser uses examples from Theodore Sider which treat as ‘real’ certain parts of a Minkowski diagram of spacetime while dismissing the rest as ‘not real.' There are three particular dissections which Dr. Feser presents before explicitly noting that Sider objected that there seems to be no justification from physics for this sort of privileging of particular sections of the Minkowski space; and also that these dissections do not really comport with the usual ideas of presentists regarding act and potency. In exactly the same way that Sungenis tries to make unjustified distinctions between correct and incorrect, supporters of these models would be making unjustified distinctions between real and not-real. Nonetheless, Dr. Feser offers them among his possible reconciliation models.
The fourth and final approach Dr. Feser offers fares similarly. This time, we suppose that the models of physics provide an accurate but incomplete picture of the world which needs to be patched by an appeal to metaphysics. However, just as was the case with Tycho Brahe and those who followed in his footsteps, this just seems like an overt attempt to pound a Relativity-shaped block universe into an Aristotelian-shaped hole. There simply does not seem to be any need to integrate act and potency with Relativity unless one already has a prior commitment to Aristotelianism.
Addressing Feser’s Worst-Case Scenario
Finally, Dr. Feser considers what he describes as the scenario with the worst implications for Aristotelianism. Perhaps the block universe description which can be inferred from Relativity is correct. Perhaps past, present, and future are all equally extant and it is not the case that, within the universe, anything’s future is simply potential and not actual. Perhaps the universe as a whole does not undergo change or temporal passage. Even on such a case, Dr. Feser claims, it remains true that the universe itself is contingent and could have been otherwise. As such, he states that this notion that the universe could have been otherwise indicates that the universe had a potential which must have been actualized, thereby still preserving Aristotelianism (at the very least, in the case of the universe as a whole).
However, this whole line of argument seems to simply be question begging. He does nothing to demonstrate that the universe is contingent or that it could have been otherwise. He simply asserts that this is the case. Now, there are some who might try to defend this claim by noting that we can conceive of the universe as being different than it is and that if it could have been different then it must be contingent upon some other reason for being this way instead of that (Catholic apologist Trent Horn has argued this way, in the past). However, Dr. Feser himself notes that it is a “tendentious assumption that we can deduce what is really possible from what is conceivable.” Some stronger argument must be made if we are to accept the proposition that this static, block universe is actually contingent and yet none is present in Dr. Feser’s argument.
Furthermore, as Feser acknowledges at the very beginning of his discussion on Time and Change, the very notions of act and potency were “introduced as necessary in order to make sense of the reality of change and temporal passage.” However, as we have already stated, the block universe as a whole does not undergo change or temporal passage. What is the justification for introducing these notions at all on a block universe model? If the entire reason for their adoption has been excised from our theory then it is entirely spurious to simply assert that they are still relevant to the discussion.
At this point, Dr. Feser would likely refer back to his claim that the block universe has an essence which is distinct from its existence to justify his appeals to act and potency. However, this does not seem to provide an escape from the allegation of question begging as, again, Dr. Feser simply asserts that the block universe’s essence would be distinct from its existence without demonstrating this. Certainly, on his view, it is possible for a thing to have an essence which is not distinct from its existence, as he would argue that this is exactly the case for a First Cause or pure-actuality which he believes to be the causal root of all reality. Even if one were to admit the notions of essence and existence, it is not trivially clear that the two are distinct in the case of a block universe. And this is to say nothing of non-Aristotelian views which find no cause to introduce a notion of essence, in the first place!
All that being said, Dr. Feser is not wrong to say that there may yet be ways in which Relativity and Aristotelianism can be reconciled. It is true that we as yet have no reason to think that Relativity necessarily contradicts Aristotelianism in general or act and potency in particular. However, neither do we have any reason to think that act and potency are necessary to our metaphysics and that we therefore must find some way to reconcile them with Relativity.
Thus far, we have limited the scope of our scientific discourse to discussions of the Special Theory of Relativity, which on its own has called for a sweeping reassessment of our notion of Time even if one still remains committed to Aristotelianism! However, Special Relativity is far from the end of the road. Indeed, the General Theory of Relativity paints an even stranger picture of time– a picture in which Time, itself, curves and stretches and bends. Quantum Mechanics confuses the issue even more, giving evidence that particles do not necessarily even have definite positions in Time and Space. In fact, it is even possible that Time and Space are themselves not even fundamental to the universe, but are rather simply emergent properties of patterns within the universal wave function. In general, the closer we get to describing the fundamental behaviors of the universe the farther those descriptions depart from the everyday experiential notions of Time and Change which informed Aristotle’s notions of act and potency.
There does not seem to be any more need to bootstrap Relativity into Aristotelian notions of Time than there is to try to bootstrap modern cosmology into Aristotelian notions of geocentrism or modern astrophysics into Aristotelian notions of aether or modern chemistry into Aristotelian notions of the natural elements. As such, I will continue to hold that Aristotle’s metaphysics are every bit as antiquated and outmoded as are his physics.
 Feser, Edward. “Actuality, Potentiality, and Relativity’s Block Universe.” Neo-Aristotelian Perspectives on Contemporary Science, Edited by William M.R. Simpson et al, Routledge, 2018; pp. 61-62
 Ibid., pp. 61-62
 Ibid., p. 71
 Ibid., pp. 77-80
 Ibid., pp. 82-84
 “Relativity of Simultaneity,” https://en.wikipedia.org/wiki/Relativity_of_simultaneity, Accessed March 15, 2020