There is a common notion I’ve seen that quantum mechanics somehow gives credence to idealism. Here, I want to address what I believe are the sources of these misconceptions as well as explain in detail why they are wrong and why quantum mechanics is perfectly compatible with a materialist view of the world. This article will largely focus on a dialectical materialist framework, as I understand it, borrowing some ideas from other philosophical schools as well, including that of contextual realism.
Bell’s Theorem and Local Realism
There is some confusion around Bell’s theorem. It is often said that Bell’s theorem shows the world is “not locally real” or that it debunks “local realism.” A Nobel prize was recently awarded precisely for testing Bell’s theorem, and this is how it is often reported. In almost all contexts, “realism” refers to the belief that there exists an objective reality independent of the observer, and thus many people interpret this to mean, somehow, quantum mechanics disproves that objective reality exists (I have even seen this written in academic papers!). Yet, this is not what “realism” means in this context in the slightest.
Albert Einstein had put forward what he called the “principle of locality” which he defined it in terms of the separability of objects. That is to say, Einstein believed that physical reality should be reducible down to individual objects that can be in principle isolated from one another. These objects would always have unique properties that they carry around with them at all times that are localized to them in space and time.
If one asks what is characteristic of the physical world of ideas independently of quantum theory, the following becomes apparent: the concepts of physics refer to a real external world, that is, they are ideas of things that claim a real existence independent of the perceiving subjects (bodies, fields, etc.), which ideas, on the other hand, are brought into as secure a relationship as possible with sensory impressions. It is also characteristic of these physical things that they are thought to be ordered into a space-time continuum. Essential for this ordering of things introduced in physics also seems to be that at a certain time these things claim an independent existence as far as these things are located in different parts of space. Without the assumption of such independence of existence of spatially distant things from each other, which initially stems from everyday thinking, physical thinking in the sense familiar to us would not be possible.
— Albert Einstein, “Quanten-Mechanik und Wirklichkeit”
Einstein had also worked with the physicists Boris Podolsky and Nathan Rosen to publish another paper entitled “Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?” In that paper, they express concern over entanglement whereby particles seem to share states with one another and not even possess definite values in and of themselves. This is why you can only make a probabilistic prediction in quantum mechanics: it simply does not assign definite values to particles at all times.
Einstein’s desire for separability would require adding additional “hidden variables” to the theory which would allow for particle states to be described in such a way that they would have definite values at all times. John Bell would later publish his famous theorem sometimes just referred to “Bell’s theorem” specifically in response Einstein, Podolsky, and Rosen. In Bell’s response, he pointed out that if quantum mechanics were to be reformulated such that Einstein’s desire for separability were to be met, then it would have to violate something known as Lorentz invariance. This is just a technical term to say it would require one particle to be able to affect another in a way that can travel faster than the speed of light — superluminal effects — which would violate the theory of special relativity. This is problematic because, well, our best physical theory is quantum field theory which relies on special relativity. This ultimately means that Einstein’s desire could not be met without contradicting our best theory of nature.
In a theory in which parameters are added to quantum mechanics to determine the results of individual measurements, without changing the statistical predictions, there must be a mechanism whereby the setting of one measuring device can influence the reading of another instrument, however remote. Moreover, the signal involved must propagate instantaneously, so that such a theory could not be Lorentz invariant.
— John Bell, “On the Einstein Podolsky Rosen Paradox”
Bell referred to this violation of Lorentz invariance through superluminal effects as something “grossly nonlocal.” Ever since Bell’s paper, people started to refer to violations of Lorentz invariance as “nonlocal” and thus a theory that is Lorentz invariant became referred to as “local.” This, however, is rather confusing, as recall Einstein’s notion about locality dealt with the separability of objects. There is a distinction to be made here between superluminal effects and separability, which are subtle but not entirely obvious, and Einstein had originally not made the distinction. However, these days nonlocality almost exclusively means superluminal effects.
In the paper by Einstein, Podolsky, and Rosen, they repeatedly referred to notions of “reality” and what is a reasonable criterion to expect of a theory that is a “complete description of reality,” and hence, the notion of separability became later just referred to as “realism.” When “realism” is talked about in reference to Bell’s theorem, it is rather misleading as it is typically used to refer to belief in an objective reality independent of the observer. However, in the case of Bell’s theorem, it instead refers to the fundamental separability of objects, the reducibility of nature down to things-in-themselves which have definite values at all times (sometimes called value definiteness).
It is sometimes also stated that the term “realism” means that it is possible to use hidden variables to predict the outcome of an experiment with certainty as opposed to standard quantum mechanics which is inherently probabilistic. However, I do not think absolute determinism is actually particularly important.
Take, for example, Michael Zurel’s hidden variable model (see this paper). It treats measurements as something which disturbs what it is measuring and randomizes its values in a way that is fundamentally unpredictable, and is thus nondeterministic. This is still considered a hidden variable model precisely because, despite this stochastic element, every object in the model has well-defined properties at all times, localized to themselves. Even if you cannot predict the outcome with certainty, particles always are treated as if they have definite values at all times.
Indeed, “realism” here does imply hidden variables as a necessary logical consequence of saying that objects are isolatable, as this “variable” would either be a well-defined property or at least a function that maps to a well-defined property when measured, that is fully localized and isolatable to a specific object and never spread across multiple objects. There have even been some attempts to extend Bohm’s pilot wave model in the literature that abandon absolute determinism in the model when dealing with particle creation. Absolute determinism is ultimately not the crux of the issue.
Dialectics and Things-in-Themselves
This rejection of the separability of objects is not even a new idea unique to quantum mechanics. It is, in fact, fundamental to dialectical materialist philosophy going back to the 19th century and Friedrich Engels’ Dialectics of Nature which abandoned the ancient materialist philosophy that came before it. Ancient materialist philosophy divided the universe into concepts of the mind and things-in-themselves, for example, the rock in the real world (the thing-in-itself), and the concept of that rock in the mind. It was imagined that the more someone studied the rock, the “closer” the concept in their mind would converge to the thing-in-itself.
However, this view led to many intractable philosophical problems, such as the mind-body problem, and was abandoned by various materialist philosophers in the 19th century. What replaced it was a different viewpoint whereby the very existence of the “thing-in-itself” is rejected (some pushed back on this notion, like Lenin). The philosophers of old divided the world into the world of the mind (the phenomenon) and the world of things-in-themselves (the noumenon). Often an abandonment of the notion of the thing-in-itself is treated as a retreat to idealism. If one adopts this dualistic framework, then abandoning the world of things-in-themselves would leave one with only the world of the mind. However, the point Engels was ultimately getting at was not that we should abandon a belief in objective reality, but that reality is not made up of things.
Qualitative things are, in a sense, abstractions. For example, consider a scatter plot with millions of data point and a trend line drawn through it. The trend line is an abstraction of the data set. It does not add any new information to it, but rather, it summarizes the information that is already there. If you could somehow hold all the data points in your head simultaneously and contemplate them all at once, you would find the trend line to be rather redundant and would wonder why it was bothered to be drawn at all, as you would already “know” that information. However, the trend line is drawn precisely because such a thing is difficult. It abstracts the data into a simplified version of particular properties of the data that might be important to remember.
In a similar sense, the universe is not composed of “things” at all. As Engels stresses in Dialectics of Nature, it is always impossible to draw a hard-and-fast line between any two things at all, either in time or in space. Consider drawing a precise boundary to where your cat begins and where the world outside the cat ends. Consider drawing a sharp boundary as to where your cat’s life actually begins (and when it has ended, if it has passed away). Consider, for example, the thought experiment of the Ship of Theseus. You could apply Theseus’ paradox to your cat too, if you wish, or even to yourself.
Often, Engels is misinterpreted as claiming that the universe always develops in sudden jumps and gradual change does not exist. I am not aware of where this interpretation originates, as a direct reading of Engels clearly states that it is precisely the opposition: the transition between two qualitative things (either in space or in time) only appears sudden with a surface-level analysis. A closer inspection will always reveal these changes to be connected through an infinite series of quantitative steps.
Hard and fast lines are incompatible with the theory of evolution. Even the border-line between vertebrates and invertebrates is now no longer rigid, just as little is that between fishes and amphibians, while that between birds and reptiles dwindles more and more every day. Between Compsognathus and Archaopteryx only a few intermediate links are wanting, and birds’ beaks with teeth crop up in both hemispheres. “Either-or” becomes more and more inadequate. Among lower animals the concept of the individual cannot be established at all sharply. Not only as to whether a particular animal is an individual or a colony, but also where in development one individual ceases and the other begins (nurses).
For a stage in the outlook on nature where all differences become merged in intermediate steps, and all opposites pass into one another through intermediate links, the old metaphysical method of thought no longer suffices. Dialectics, which likewise knows no hard and fast lines, no unconditional, universally valid “either-or” and which bridges the fixed metaphysical differences, and besides “either-or” recognises also in the right place “both this-and that” and reconciles the opposites, is the sole method of thought appropriate in the highest degree to this stage. Of course, for everyday use, for the small change of science, the metaphysical categories retain their validity.
— Friedrich Engels, “Dialectics of Nature”
“Things” are metaphysical abstractions. They, like the example with the trend line, merely distill down important parts of the natural world that are relevant to us into simplified categories that are easier to understand and remember. If, somehow, you could hold all the data points on scatter plot in your head simultaneously, then no one would ever need to draw a trend line. It would be redundant and you would already “know” the information it represents. In a similar sense, if it was possible to hold the entirety of nature in our heads at once and contemplate it simultaneously, we would have no need to posit “things” at all. All “things” would be entirely redundant.
We slice up the reality surrounding us into objects. But reality is not made up of discrete objects. It is a variable flux. Think of an ocean wave. Where does a wave finish? Where does it begin? Think of mountains. Where does a mountain start? Where does it end? How far does it continue beneath the Earth’s surface? These are questions without much sense, because a wave and a mountain are not objects in themselves; they are ways which we have of slicing up the world to apprehend it, to speak about it more easily. These limits are arbitrary, conventional, comfortable: they depend on us (as physical systems) more than on the waves or the mountains. They are ways of organizing the information which we have or, better, forms of information which we have.
— Carlo Rovelli, “Reality is not what it Seems”
However, it is of course, not possible to achieve this, so the entire purpose of the dialectical framework is to construct a logical system to deal with abstract categories with this in mind. I have seen various instances where people remember and regurgitate Engels’ axioms but do not seem to understand the essence of them. His axiom of the “change of quantity into quality,” for example, refers to the impossibility to draw hard-and-fast lines between two “things.”
The notion of contradiction central in Engels’ work arises from the fact that, because these qualitative “things” are mere abstractions, when we look underneath them and investigate them more closely, we never find that all aspects of the internal structure of that thing coincide with our abstraction. In the analogy with the scatter plot and the trend line, there may be outlier data point, for example, that lie outside of our expectation based on the trend. If these contradictions accumulate, they can change the qualitative character of the trend line.
These contradictions are what give rise to paradoxes such as the Ship of Theseus paradox, or the teleporter paradox whereby we ask if a person who is destroyed and then later reconstructed is the “same” person. For many things, we have a sense of continuity associated with them, such as, you may call your cat today the same name as you did yesterday, even though upon further inspection it has changed. Why do you still call it the same name, then? Precisely because the abstraction does not include those particular details. It is, by its very nature, “fuzzy,” and so this allows us to continue applying the same name to an object even if it undergoing continuous change.
However, if we scrutinize any of these categories more closely, we run into philosophical difficulty and various paradoxes. For Engels, these paradoxes are not a problem in the sense that we need to logically resolve them. Rather, they are an inherent feature to abstract categories themselves that is impossible to exorcise. We have to use abstract categories, so we should use them in a way where we keep in mind that they contain internal contradictions upon closer inspection, we keep in mind that they are “fuzzy” and do not have precise boundaries between other objects we identify in nature. In other words, Engels was attempting — although never quite finished — to develop a logical system that could take this into account, rather than to merely abandon the usage of abstract categories.
Indeed, to some extent, it has always been both necessary and proper for man, in his thinking, to divide things up, and to separate them, so as to reduce his problems to manageable proportions; for evidently, if in our practical technical work we tried to deal with the whole of reality all at once, we would be swamped…However, when this mode of thought is applied more broadly…then man ceases to regard the resulting divisions as merely useful or convenient and begins to see and experience himself and his world as actually constituted of separately existent fragments…fragmentation is continually being brought about by the almost universal habit of taking the content of our thought for ‘a description of the world as it is’. Or we could say that, in this habit, our thought is regarded as in direct correspondence with objective reality. Since our thought is pervaded with differences and distinctions, it follows that such a habit leads us to look on these as real divisions, so that the world is then seen and experienced as actually broken up into fragments.
— David Bohm, “Wholeness and the Implicate Order”
Materialism and Holism
If, indeed, it is impossible to draw hard and fast lines between things, then, in a sense, everything flows into everything else. This would apply to all things, including causality itself. If a particular cause were to be associated with a particular effect, this identified cause would, too, be an abstraction, which would break down upon further analysis and flow into other causes.
Consider, for example, pushing a ball down a hill. Clearly, you pushed the ball down the hill. So, in a very abstract sense, you are clearly the cause. Yet, if you inspect the ball more closely, you will find that the very precise motion of the ball is not solely determined by you. It would’ve also been very subtly affected by the wind and the shape of the ground. Indeed, even a gravitational wave passing through the earth from a distance galaxy would have subtly, and imperceptibly, altered the ball’s position. We can only say that “you” caused the motion of the ball rolling down the hill if we abstract away all the very subtle alterations to its position and focus on the “big picture” relevant to the discussion (you, in this case, would be the most significant contributor to the motion of the ball).
While, often, only looking at the “big picture” is perfectly fine in everyday use, occasionally it fails as the underlying contradictions that were not considered can cause a system to behave in a way that was not predicted or expected. Hence, in dialectical materialist philosophy, it has always been stressed that it is impossible to understand something in complete isolation, but only with its interconnections to everything else. Engels speaks of everything subtly being both the cause and effect of everything else, and thus cause and effect, in a sense, run into each other.
[C]ause and effect are conceptions which only hold good in their application to individual cases; but as soon as we consider the individual cases in their general connection with the universe as a whole, they run into each other, and they become confounded when we contemplate that universal action and reaction in which causes and effects are eternally changing places, so that what is effect here and now will be cause there and then, and vice versa. None of these processes and modes of thought enters into the framework of metaphysical reasoning. Dialectics, on the other hand, comprehends things and their representations, ideas, in their essential connection, concatenation, motion, origin, and ending.
— Friedrich Engels, “Anti-Durhing”
Louis Althusser referred to this notion as “overdetermination” in his book For Marx. Sometimes, overdetermination is understood to be the notion that any effect has many causes where a single cause is sufficient to explain the effect. Althusser’s notion is almost the opposite. It instead states that every effect is overdetermined by everything else, where all things are necessary to fully explain the effect. In the same way when we talk about “things” we are abstracting the natural world based on properties that are relevant to us, when we talk specific causes that led to an effect, we are abstracting the causes that we see as the most relevant and important from our own perspective. As Richard Wolff put it, what overdetermination suggests is that if you label something as a particular cause of an effect, you are doing a lot more than merely identifying the cause, but you are also identifying something about yourself.
Thinking in terms of overdetermination means that each aspect…is approached as the combined effect of all the other aspects…This idea is best described by the word “constitutivity.” Each aspect…is constituted — literally created — as the com- bined effect of all the other aspects. Thus no aspect can exist independently of the others. which create it. No one aspect can exist prior to the others as, for example, their ultimate cause. It follows that each aspect owes its existence to the others. Each is the result of the interactions among all the other aspects of society. If you think about this, you can see that this idea of overdetermination must also mean that every aspect…is always a cause and an effect. Each aspect plays its particular role in shaping — that is, in causing the existence of — every other…The Marxian theoretical commitment to overdetermination thus leads directly to the view that everything…is forever changing. This theory rejects any notion of stasis, the idea that some aspects of life are fixed. Rather, every event, person, institution, and relationship is understood as always changing.
— Richard Wolff and Stephen Resnick, “Economics: Marxian versus Neoclassical”
The physicist Dmitry Blokhintsev — who is most famous for creating the concept of the graviton—was also a dialectical materialist and seemed to have similar ideas in mind. When Einstein wrote his paper on his principal of locality being defined in terms of the separability and isolatability of objects, Blokhinstev responded with scathing criticism. Blokhinstev pointed out that, from his philosophical perspective, it is nonsense to talk about being able to isolate objects down to things-in-themselves, but that all things can only be understood in their interconnections with everything else.
The isolation of microsystems, which was considered as fundamentally possible from the point of view of classical concepts, in reality, due to the finiteness of interactions, turns out to be unrealizable…causality formulated in classical physical theory…is an abstraction, an approximation. This circumstance was long and well known to the founders of materialist dialectics.
— Dmitry Blokhintsev, “Критика идеалистического понимания квантовой теории”
Later on, Blokhintsev would write an extensive book on this subject. In it, he argues that in a natural world where things cannot be separated from their environment, a materialist has to abandon the notion of absolute determinism. Einstein’s concern with separability is that, if some phenomena are nonseparable, then it would be impossible to isolate that phenomenon, and thus impossible to formulate a theory of it (this was his reasoning he put forward for upholding the principle in his paper where he discusses it). Rather than treating this as a problem, Blokhintsev just accept it as a fact of nature: we can never hope to make absolute prediction because we can never fully isolate any experiments from their environment. Even in classical mechanics, Blokhinstev points out how absolute determinism is an illusion as all predictions break down eventually due to environmental effects.
The supporters of inflexible determinism are wrong in taking classical mechanics as their example: the motion predicted by classical mechanics is unstable either on account of small random deviations in the initial data or owing to the presence of random forces. No matter how small these perturbing effects may be, there always comes a time at which their consequences will predominate. This instability against slight randomness completely destroys the illusion of unambiguous prediction of the future from the initial data without subsequent correction during the process.
— Dmitry Blokhintsev, “The Philosophy of Quantum Mechanics”
Engels had argued that motion was a fundamental property of nature, that is to say, that nothing ever stands still. Blokhintsev had further pointed out that, indeed, this would seem to logically follow if you believe in nonseparability. If it is impossible to isolate things from their environment, then everything must have irreducible motion. On a large scale, as an abstraction, we can identify causes for the motion of an object, but as we get down to smaller and smaller scales, eventually we should hit a limitation where there is observed motion that appears to be fundamentally uncaused. For Blokhintsev, the apparent nondeterminism of quantum theory was thus not something very surprising, but only something to be expected.
Consider the case of a…thermostat…at zero temperature. The canonical distribution implies that the energy of the system must be as low as possible, which means that the kinetic energy…must be zero, while the potential energy…must be at the minimum. This further implies that the momenta must be zero, and the coordinates are obliged to have the one single value corresponding to the minimum potential energy. In other words…each dynamic variable is confined to a single value, with no statistical spread at all. In particular, there should be no light scattering due to molecular thermal motion. However, experiment shows that such scattering does occur at low temperatures and in the limit (at absolute zero). This shows that motion persists in some form at this temperature, where all motion should have ceased. James, Brindley, and Wood were among the first to examine this, and in their paper on the scattering of X-rays in an aluminium crystal they stated that it is necessary to assume a zero-point energy (i.e. an energy of motion at absolute zero) in order to obtain agreement with experiment. This unfreezable motion is a motion of a new (quantum) type.
— Dmitry Blokhintsev, “The Philosophy of Quantum Mechanics”
Hence, notions of nondeterminism and nonseparability should not be viewed, to the contrary of what is often stated, to be some sort of reason to abandon materialism. We should, indeed, abandon Newtonian-esque and Kantian-esque views that the natural world is reducible down to separable things-in-themselves, that the future is fully predictable like the parable of Laplace’s demon. Yet, these views were already called into question in materialist philosophy in the 1800s, long before quantum theory, so there is no difficulty in dealing with them.
Waves and Trackability
Let us imagine a simple scenario where a person named Charlie prepares two qubits (quantum bits of information) that will carried by two particles. For example, it could be two electrons where the bit values (0 or 1) will be determined by the direction of the electron spin. Charlie prepares these particles in such a way that they are said to be entangled, meaning, the values are guaranteed to be correlated with one another, and let us assume this is a perfect anti-correlation, meaning, they are guaranteed to have the opposite values (if one has the value 0, the other has the value 1, and vice-versa). Finally, let us assume that Charlie sends these two particles off to Alice and Bob who live millions of light years apart.
If the above picture is an accurate visualization, then as those qubits are traveling to Alice and Bob, they should have well-defined properties at any moment along that line, and since they are traveling along separate lines, their properties should be independent of one another. However, due to Bell’s theorem (which I will not get into detail here, but this video is great on the topic), we know this depiction cannot be right as two entangled particles have properties that are related to one another in a way where they cannot be thought of as entirely separate objects moving through space.
The fact that this depiction cannot be quite right is what caused Einstein so much worry. However, if we are already rejecting the separability of things from a philosophical standpoint, it does not seem surprising that on a fundamental level, a particle cannot be “tracked.” If you fire a cannonball from point A to point B, and you have photos of it at both locations, you can “track” it in Newtonian mathematics in the sense of being able to describe where it was at every moment in time between point A and point B.
Yet, this trackability of objects inherently implies that the object you are tracking really does meaningfully have properties reducible down to itself, that is truly does exist as a thing-in-itself. If you reject such a thing as a premise, then there is no reason to suspect at a fundamental level particles should be trackable. The lack of trackability of objects in quantum theory has often been used to endorse idealist philosophy, but, again, this is equivalent to saying an abandonment of the thing-in-itself means we have to abandon that there is a reality independent of the observer. It is a non-sequitur. Indeed, objects are not trackable, but that is merely a property of reality, not evidence that reality does not exist.
The problem is that it seems as though there cannot be any ‘objects’ in quantum mechanics, for it is impossible to simultaneously know both the position and the speed of a ‘particle.’ Thus, I cannot ‘track’ a particle in the ordinary sense of the word that is connected to the traditional notion of an ‘object.’ The upshot of this is that a lot of philosophers endorse an idealistic interpretation of quantum mechanics. Because what QM says about reality does not seem to be compatible with the traditional picture of reality as made up of objects, it is very tempting to think that QM simply does not concern reality…What is ‘reality’ in QM? It is exactly that which is captured by the tensorial formalism QM makes use of. There is no need to translate that formalism into something that lacks its bite, its special contact with reality that cannot be replicated through other means. To substitute anything else for this realism would be to lose sight of the specific dimension of reality it allows us to capture…The whole point is that reality is something which we can speak of — or which we can operate on — in definite ways. Quantum mechanics is one such way and therefore captures something of reality.
— Jocelyn Benoist, “Toward a Contextual Realism”
We have to, therefore, abandon the notion that the particles really do have an absolute position at all times in between interactions, and thus the simple picture illustrated above cannot be correct. What is correct?
A common alternative to the depiction above is to imagine that Charlie is not actually sending Alice and Bob particles at all. Between measurements, the particles do not exist as particles, but instead exist as waves, and in this case, because the two particles are entangled, they would really exist as one giant wave. Thus, in a sense, at least as it is commonly depicted, one can imagine Charlie is propagating a giant wave to Alice and Bob.
Let’s assume that even though both Alice and Bob receive their qubits at the same time (i.e. the wave reaches them at the same time), but Alice decides to check hers first and measure its properties. The moment she measures hers, the wave is destroyed — it is said to “collapse” — and what is left in its place are two distinct qubits. Whatever Alice or Bob measures is fundamentally nondeterministic in quantum theory, however, the correlations between them are guaranteed.
In this case, given it is a perfect anti-correlation, Alice and Bob are guaranteed to measure the opposite values for their qubit. Even though Alice does not know if hers will be a 0 or a 1 until measuring it, if she measures, let’s say, a 0, then she knows with certainty that Bob’s must be a 1. The moment Alice disturbs the wave with her measurements, it “collapses” into two qubits with definite known values.
There are certain conceptual difficulties with this picture, however, that has lead to a myriad of philosophical issues. These philosophical issues have become known as the measurement problem, and these issues have, in turn, been used to attack materialist and realist philosophy.
The first and most obvious is that there seems to be something superluminal going on here, what Einstein had referred to as “spooky action at a distance.” The moment Alice measures her particle, the wave function is said to “collapse” which is then said to, in a sense, bring both her particle and Bob’s into existence. If, somehow, it was possible to see these wave functions, then the very moment Alice measured her particle, Bob would see a change to his. Of course, this is not possible, but at the same time, it seems rather conspiratorial.
This image seems to suggest that, on a fundamental level, there is a superluminal signal being transmitted from Alice to Bob, but if Bob tries to look at the wave to see it, he just so happens to perturb it, and so there is no way he could actually be aware of this signal. Indeed, there is a proof in quantum theory called the No Communication Theorem that shows superluminal communication is impossible. It seems rather conspiratorial, doesn’t it, that the natural world — if these waves are indeed real — has underlying superluminal signaling, but just so happens to transform itself into something else when we try to observe it?
However, this kind of pseudo-nonlocality is not the even the biggest conceptual problem. Not that long ago people used to believe gravitational effects and light travelled superluminally, so if that was the only philosophical problem, no one would make a big deal out of it. No, there is a more significant problem that is derivative of the very notion of presuming there is an observer effect that perturbs the wave whenever we try to look at them.
In psychology, there is something known as the Hawthorne effect, whereby a person who is being studied — if they know they are indeed being studied — will alter their behavior. If a person alters their behavior when they are observed, then you cannot extrapolate from your observation how they would behave if they were not being observed. Similarly speaking, if we assume the act of observation in quantum theory causes some sort of wave to collapse — like a house of cards — the moment we try to observe it, leaving only particles in its place, then we cannot extrapolate from our observations what nature is like independent of our observations.
Indeed, these “wave functions” are not even visible, as they just so happen to disappear the moment we try to look at them, leaving in their place particles we can actually see. Blokhintsev had also pointed this out, arguing that it is therefore dubious to treat these wave functions as actually existing entities floating out there in the natural world.
Often, quantum theory is taught beginning with the double-slit experiment whereby photons (or electrons) produce an an interference pattern — which can only be produced by waves—on a screen. This is used to illustrate that a single particle spreads out into a wave when not being observed, and gives the false impression that you can “see” wave functions.
However, this is misleading. The interference pattern on the screen can only be formed with the combination of millions of particles. Wave functions associated with a single particle cannot be observed at all. Indeed, even the interference pattern formed on the screen by millions of particles does not contain the full information of the wave function but only a projection of it, sort of like the wave function’s “shadow” (it is a projection because the Born rule requires you square the wave function to predict statistical results, which destroys the imaginary components).
Hence, Blokhintsev was skeptical of this whole notion of presuming particles really do transform themselves into waves when you are not looking at them.
This is essentially a trivial feature known to any experimentalist, and it needs to be mentioned only because it is stated in many textbooks on quantum mechanics that the wave function is a characteristic of the state of a single particle. If this were so, it would be of interest to perform such a measurement on a single particle (say an electron) which would allow us to determine its own individual wave function. No such measurement is possible.
— Dmitry Blokhintsev, “The Philosophy of Quantum Mechanics”
Let us deviate for a second and discuss the origin of the mind-body problem. While this may seem off topic, there is a relevance here. This philosophical problem originates with the dualistic split between the supposedly unobservable world of the noumenon and the observable world of the phenomenon. If there is a whole world out there that is impossible to observe, how can it ever hope to explain what we do observe? There is an explanatory gap between these two worlds, as it is unclear how one translates itself into the other the moment we try to look at it.
Malebranche expressed the principal difficulty arising here in his own witty way, as follows: during the siege of Vienna, the defenders of the city undoubtedly saw the Turkish army as ‘transcendental Turks’, but those killed were very real Turks. The difficulty here is clear; and from the Cartesian point of view on thought it is absolutely insoluble, because the defenders of Vienna acted, i.e. aimed and fired their cannonballs in accordance with the image of Turks that they had in their brains, in accordance with ‘imagined’, ‘transcendental Turks’, and with trajectories calculated in their brains; and the shots fell among real Turks in a space that was not only outside their skulls, but also outside the walls of the fortress. How does it come about that two worlds having absolutely nothing in common between them are in agreement, namely the world ‘thought of’, the world in thought, and the real world, the world in space? And why?
— Evald Ilyenkov, “Dialectical Logic”
In an incredibly similar sense, the same problem arises in quantum theory. If we presume that the natural world exists as unobservable waves that transform themselves into what we observe the moment we look at them, there seems to be an explanatory gap as to how this process actually occurs, how it is that the act of measurement actually perturbs invisible waves so that they transforms themselves into visible objects. This is the essence of the measurement problem.
Despite the striking similarities between the two problems, there is a slight difference. In the noumenal world of dualism, it is not merely that you cannot observe it, but you simply cannot say anything about it at all, while in quantum theory, you can at least describe these waves using the Schrodinger equation, even if you can never see them. Moreover, when you make a measurement, the transformation of a wave into a particle causes a “jump” which deviates from the Schrodinger equation (the former is linear, but the latter is nonlinear). Hence, there is also a mathematical aspect here — not simply a purely philosophical one — that has to be addressed. In other words, philosophical solutions to this problem have to also be compatible with the technical aspects of the theory. However, this aspect turns out not to cause any sort of concerns in the direction that these problems will be approached later in this article.
Proposed solutions to the measurement problem seem to also parallel solutions to the mind-body problem. For example, we could just dismiss the measurement problem and say the explanatory gap does not need to be closed because “nature just does that, there are just two realms where one converts itself to another whenever we look at it.” This parallels dualism which treats the mind-body problems as something unsolvable because there really is an unbridgeable gap between the realm of the observed and the realm outside of all possible observation.
There are issues to this approach as wave functions are a result of a very specific mathematical formalism. Prior to Schrodinger, Heisenberg had formulated quantum mechanics in terms of matrix operations without the Schrodinger equation. Quantum mechanics can also be formulated using Feynman’s path integrals, or as a statistical theory involving ensembles over phase space. The point here is that the wave formulation is a result of a very specific mathematical formalism, and so treating it as if there really exists a secondary realm beyond all possible observations of waves in Hilbert space is rather dubious.
Let us go back to our discussion of Blokhintsev. He had pointed out how, if we cannot see this world of wave functions, we should be skeptical about treating them as if it even actually exists. Indeed, wave functions do not even exist in traditional spacetime, but a more abstract space called a Hilbert space, so it is difficult to even conceive of what it means to say they exist as normal objects.
However, there is something we have to be very careful of here. You see, we can also say the same thing of the noumenon in the mind-body problem. It is also defined as something that lies outside of all possible observation, as, by definition, it is a separate world from the world of experience. So, naturally, it seems it could also be argued the noumenon should be discarded as a useful concept in philosophy.
Yet, if we simply discard the noumenon, and touch nothing else, we are left simply with the phenomenon — the world of the mind. This leads to a regression into idealism. Indeed, this is the same trap many philosophers and physicists have fallen into when interpreting quantum mechanics. They come to realize that, yes, if we cannot observe these waves, we should discard their existence and only stick to what we observe. Yet, by doing so, they end up reaching the conclusion that there is no objective reality independent of our observations.
Most working scientists hold fast to the concept of ‘realism’ — a viewpoint according to which an external reality exists independent of observation. But quantum physics has shattered some of our cornerstone beliefs.
— Anton Zeilinger et al, “An experimental test of non-local realism”
What has to be clarified, thus, is how we can discard the noumenon without devolving into idealism, and, by extension, how we can discard waves as ontological entities without devolving into speak of “observer-dependence” or any other subjectivist, idealist language.
Contextualism Rather than Subjectivism
Why is the mind-body problem so tempting in the first place? Why does it seem to intuitive to posit a dualistic split between the world we experience every day, and some sort of world outside our experience which cannot be observed? There are likely many reasons people find this intuitive, however, one of the largest one of these seems to be a conflation between contextuality and subjectivity.
You see, every single one of us experiences the world differently. We all have our own experiences unique to us which it is impossible for anyone else to share. No one can know what it is like to be me. I can never know what it is like to be my cat. This subjective nature of experience inclines us to believe that experience is something unique to subjects, and thus, without the existence of subjects, there would be no experience at all.
Hence, the conclusion typically drawn is that our raw sensual experience — that is to say, what is thought of as opposed to thought — is only reducible down to the subject and not reality independent of the observer. It is thus deemed to be not “real.”
Philosophers then dub it with names such as “subjective” experience or “phenomenal” experience to express its subjective character. This inherently implies a contrast with some sort of “objective” experience or “noumenal” experience, where these latter categories refer to what nature is really like rather than how it is represented in our minds.
Yet, this is a subtle fallacy — a very subtle fallacy which seems to be trip up the overwhelming majority of philosophers. Just because something is unique to you does not make it subjective. My favorite song is subjective because, independent of subjects, it is meaningless to even speak of “favorite songs.” Something subjective is reducible down to subjects, but not reducible to anything objective. However, there are other ways in which something can be unique to all conscious observers, yet it still also be reducible down to reality independent of the observer.
Consider, for example, the velocity of an object. It is impossible to define the velocity of an object without specifying another object which serves as a frame of reference. If the velocity of a train is said to be 150 km/h, there is a hidden implication that this is relative to the earth. If I am standing still on the earth, then I will perceive the train traveling at 150 km/h. If I hop in a car traveling 50 km/h, I will see the train, in a sense, “slow down” to 100 km/h. Why? Because, again, velocity is relative, and hence, if I change my frame of reference — my point of view — I will actually physically see different velocities.
Every individual occupies a particular frame of reference and, in some instances, view the same object as having different velocities. A person in the car and a person outside the car would see the train traveling at different speeds from their point of view. Does the fact they observe different things from their unique point of view demonstrate that the velocity is subjective? No, of course not! Velocity is not subjective, but rather, it is reference frame dependent, or, in more concise language, it is context-dependent.
Indeed, observers will occupy unique frames of reference, but it is still meaningful to discuss, for example, the velocity of a train relative to a rock. The rock is not a conscious entity yet it can still meaningfully be discussed as a frame of reference, that is to say, what the train’s velocity would be from the “point of view” of the rock. In real world, in physical reality, certain properties of nature really do change depending on your context within it. Hence, the reason two observers can disagree over the velocity of an object is not because they are subject, but despite of it. The natural world does not care that they are conscious subjects. Rather, humans are objects in the physical world just like any other objects, and thus, just like any other object, have to define properties in the world based on the reference frame which they occupy.
This is the approach we should take to experience. It is not subjective simply because it is unique to each and every one of us. No, it is unique to each and every one of us because we all occupy a unique position in reality. None of us stand in the same location, have the same history and memory, have the same physical body, so on and so forth. We all occupy a very unique context in the world, and so it is natural that we would all perceive things differently. Nobody could experience the world exactly as I experience unless their context was identical to mine, which would require them to literally be me, and thus cease to be a different person. The contextual nature of reality necessitates the impossibility of ever knowing exactly what it is like to be someone else.
However, the contextual nature of reality also means that experience does not have to be interpreted as “subjective.” Nature is just context-dependent, in other words, point of view dependent. We just so happen to occupy a unique context, each and every one of us, and so naturally, we all experience the world differently. Our unique experiences of reality is not because we are subjects, but in spite of it. We can thus dispense of the language our experiences being some sort of subjective “reflection” of reality or the “appearance” of reality, or a “representation” of reality.
Rather, our experiences are reality as it experienced from a specific context. What is “subjective” is not reality, it is not what is thought of, but rather, it is thought, it is what we take reality to be. The moment I begin to interpret reality, I leave reality and enter into subjective evaluation of it, which is prone to error if I am not careful. However, reality itself can never be in error, it is never true nor false. Reality merely is what it is, independent of our interpretation of it, independent of what we take it to be.
We can thus, in addition to discarding the noumenon, also discard the phenomenon. Both dualistic categories can be thrown out as they are both flawed methodologies of interpreting the world.
‘Phenomenal,’ etymologically and philosophically, means appearing. Why should we describe experience as ‘appearing’? As, that is, appearing to someone, to a subject, as is logically required by the syntax of the verb? This turn of phrase, familiar though it may be within a certain philosophical tradition, nonetheless sounds strange. According to the regular syntax of ‘experience,’ our ‘experiences’ do not ‘appear’ to us. We have them, in a way that requires the progressive form: ‘I am having an experience.’ A kind of direct transitivity seems to be involved: an internal accusative. As a matter of fact, experience just is its ‘being had.’ Doesn’t talk of experience ‘appearing’ — or to put it in technical terms, its ‘phenomenality’ — already create a gap between an experience and its being had that cannot exist? I would be inclined to say that an experience does not appear; it just is what it is.
— Jocelyn Benoist, “Toward a Contextual Realism”
There is some resistance from materialist philosophers for treating experience as real. How can experience be real if reality is material and matter cannot be experienced? The question is, in fact, based on a false premise. Matter obviously can be experienced, or else how did we derive the concept of matter in the first place? It is clearly derived from our observations of the world, it is derived from reality.
You see, on a very surface level, we begin to identify the most obvious patterns we can sense, grouping things by their color, “redness,” “blueness,” and by their sound, “quietness,” “loudness,” by their texture, “smooth,” “rough,” so on and so forth. After this initial categorization, we begin to find certain relationships and patterns between these categories and then form them into much more complex groupings. Take, for example, an elephant.
Elephants have a particular shape unique to them, they are grey in color, they make trumpeting noises, with a rough wrinkly texture to their skin, so on and so forth. All these surface-level categories, we realize they come together to form a much more complex category, that of an elephant.
We apply this to many things in nature forming many complex categories: trees, birds, cats, dogs, flowers, so on and so forth. Some of these categories can be grouped together even further. Flowers and trees have more similar underlying properties than birds, dogs, and cats, so we can generalize the former into plants and the latter into animals.
Yet, even upon further inspection, we find more similarities underlying similarities between plants and animals, between rocks and stars, an underlying structure that ties them all together: they all have an atomic structure. They are all made of elements on the periodic table.
Our concept of matter is not something derived entirely independent of experience. It is the result of beginning with very abstract, surface-level categorizations of reality, and then finding what all those categories have in common. As we find connections between these categories, we begin to reduce them into their fundamental constituents. It is not that all our concepts are reducible down to objects of qualia, but that objects of qualia are just the most surface-level objects we create in order to categorize experience, and thus everything ultimately comes back to experience.
At no point did we ever leave experience, all of this is derived from experience. It is just that when we get to more reduced and complex categories, the connections to experience become less obvious. Simple surface-level categories are, by their very nature, surface level. They are easy for anyone to understand. You can explain to a child what is meant by the color red, yet explaining to a child what a subatomic particle is might be a bit more difficult.
Yet, no explanation would be devoid of experience. You would need to show people what kind observations led to the concept of the elements on the periodic table, or the concepts of subatomic particles, or even quantum fields. All these things have to be demonstrated to understand it. All our scientific knowledge depends upon observation, so the idea that it is somehow independent of experience is a falsehood.
Indeed, if we materialists are correct and the world is material, why wouldn’t experience also be material? The notion that experience is merely a “reflection” of reality and is therefore, in a sense, not real, is a bizarre notion. How can something that is not real even be? It is bizarre to believe that all of nature is material, yet somehow the human brain is capable of producing something nonmaterial. One must demolish the demarcation between matter and experience in order for materialism to make any sense at all.
The whole problem thus boiled down to resolving whether thought could, in general, be distinguished from man as a material, sensuously objective creature, and to fixing it and considering it from the very beginning as something independent, in contrast to everything corporeal, sensuous, and material; or whether thought should be understood as a property (‘predicate’) inseparable from man…Feuerbach considered that the basic problem of philosophy was thus, and only thus, put on a firm footing of fact, and so, naturally, resolved in favour of materialism. Thought was the real function of the living brain, and was inseparable from the matter of the brain. If we had brain matter in mind, then it was quite ridiculous in general to ask how thought was ‘linked’ with it, how the one was connected with the other and ‘mediated’ it, because there simply was no ‘one’ and ‘the other’ here, but only one and the same thing; the real being of the living brain was also thought, and real thought was the being of the living brain. That fact, expressed in philosophical categories, revealed ‘the immediate unity of soul and body, which admits of nothing in the middle between them, and leaves no room for distinction or even contrast between material and immaterial being, is consequently the point where matter thinks and the body is mind, and conversely the mind is body and thought is matter’. The ‘identity’ of thought and being, so understood, must also (according to Feuerbach) constitute an axiom of true philosophy, i.e. a fact not requiring scholastic proof and ‘mediation’.
— Evald Ilyenkov, “Dialetical Logic”
On “Matter”
If we were to discard the dualistic categories the phenomenon and the noumenon, what categories should we replace it with? I have only found one answer to this that I find consistent and satisfactory: Jocelyn Benoist’s distinction between the ideal and the real.
At first, this may seem to be the same categories as the dualistic split between the noumenon and the phenomenon. However, they are drastically different and more logically consistent. In the dualistic categeries, both of these consist of independent “worlds” in the sense that they are treated as if they exist. Additionally, they both are said to have an experiential and object component to them. There is said to be phenomenal objects (concepts in the mind), phenomenal experience (or “subjective experience”), noumenal objects (things-in-themselves), and noumenal experience (what those things are really like).
In Benoist’s framework, the category of the ideal only includes objects, not experience. In fact, recall, that experience is reality. Rather, the category of reality merely contains being and nothing more, i.e. it does not contain objects, it does not contain “things.”
With these categories, it becomes meaningless to speak of abstract concepts, ideal objects, as if they have “existence,” as existence requires being which is only categorically associated with reality. It is not that abstract concepts do not exist, rather, it is a category mistake to even ask whether or not they exist.
This is true for all abstract concepts. It is equally meaningless to ask if “redness” exists or abstract mathematical objects like a “circle” as it is to ask if an abstract “atom” as such exists. There is a lot of hype from idealists around surface-level abstractions such as “redness.” They call these surface-level abstractions “qualia” and try to demarcate them as special from other abstractions such as “atoms,” yet, from this standpoint, there is simply no demarcation: they all belong to the category of the ideal and it is a category mistake to even ask if they exist.
If none of these can be meaningfully said to exist, then what does exist? What exists are objects in context. That is to say, when the gulf between the ideal object and real experience is bridged in context, along side a particular real experience. While the abstract concept of a tree does not meaningfully exist, if I see a tree and point to it and say, “that’s a tree,” if I apply the concept to identify something in a real context, then the abstract category of the tree ceases to be abstract and becomes that tree, in reality, and thus acquires being.
In other words, objects can only be treated as real objects when they are attached to reality. This is true for all ideal objects — without any demarcation between them as is popular in contemporary philosophy. There is no different treatment here for “qualia” objects as there is for physical objects like atoms, or mathematical objects like circles. When “redness” becomes attached to something, when I can point to a red object and “that’s red,” I am referring to something real. When I point to a circular sign and say “that’s a circle,” then that is a real circle. If I point to atoms under an electron microscope and say “those atoms,” then those atoms are real.
With this in mind, we can begin to discuss the concept of matter and its relationship to philosophy. What is even matter? What is meant by “matter” in materialist philosophy does not refer to the definition in the physical sciences of a massive particle, but rather, it refers to whatever categories we have of nature that are the most reductionist, i.e. the fundamental constituents, what “ties everything together,” so to speak. This is an inherently moving target as the progress of science changes this all the time, from atoms to subatomic particles to, these days, quantum fields. Materialist philosophy is philosophy, not physics, so it is not dependent on whatever these fundamental constituents are.
Matter is nothing but the totality of material things from which this concept is abstracted, and motion as such nothing but the totality of all sensuously perceptible forms of motion; words like matter and motion are nothing but abbreviations in which we comprehend many different sensuously perceptible things according to their common properties. Hence matter and motion cannot be known in any other way than by investigation of the separate material things and forms of motion, and by knowing these, we also pro tanto know matter and motion as such.
— Friedrich Engels, “Dialectics of Nature”
Yet, despite these fundamental constituents being derived from experience as mentioned in the previous section, when we talk about “matter” in the abstract, we are not talking about anything real. We are talking about a pure abstraction, not a particular form of matter in a particular context, but something so abstract that it seems utterly detached from experience, something that is not even meaningfully real.
It is this detachment of matter as a purely abstract concept that leads to the misconception that there needs to be some sort of demarcation between matter and surface-level abstractions, that is to say, the objects associated with qualia. This demarcation is not necessary, however, because once we speak of real matter in a specific context, when we discuss specific forms of matter, if we look at specific experiments and observations from which we derive the concepts of matter, then the supposed need for a demarcation entirely disappears. The seeming gulf betwen the abstract concept of matter and experience is bridged in context, when abstract matter becomes real matter, i.e. when we look at the actual observations that led to the development of notions of categories such as quantum fields.
Matter as such is a pure creation of thought and an abstraction. We leave out of account the qualitativative differences of things in lumping them together as corporeally existing things under the concept matter. Hence matter as such, as distinct from definite existing pieces of matter, is not anything sensuously existing. When natural science directs its efforts to seeking out uniform matter as such, to reducing qualitative differences to merely quantitative differences in combining identical smallest particles, it is doing the same thing as demanding to see fruit as such instead of cherries, pears, apples, or the mammal as such instead of cats, dogs, sheep, etc., gas as such, metal, stone, chemical compound as such, motion as such.
— Friedrich Engels, “Dialectics of Nature”
Contextual Quantum Mechanics
With all this in mind, we finally have the tools to actually address the conceptual problems of quantum theory, to interpret the theory in a way that dissolves the measurement problem without devolving into idealism. Indeed, Engels had written in Anti-Durhing that “Modern materialism embraces the more recent discoveries of natural science.” What would be the purpose of materialist philosophy if it could not adapt to and develop alongside the discoveries of the natural sciences?
According to philosopher Hilary Putnam, any serious philosophical position, both realistic and anti-realistic, must take into account “the most fundamental physical theory we have (quantum mechanics)”. For his part, the theoretical physicist Carlo Rovelli calls not to interpret quantum mechanics according to a philosophical orientation, but rather to “allow the discoveries of fundamental physics to affect our philosophical orientations.”
— Francois-Igor Pris, “Contextual Realism and Quantum Mechanics”
Blokhintstev was on the right track: if these noumenal wave functions can never be observed, then treating them as autonomous entities is a rather dubious metaphysical construct. However, in order to not devolve into idealism, we must avoid the conclusion that quantum theory is observer-dependent. Rather, in the same way we avoided idealism by reinterpreting subjective reality to contextual reality, we can apply the same reasoning here: quantum theory is context-dependent.
Real particles, as opposed to abstract particles, only exist in a particular context, that is to say, from a particular frame of reference. In order to acquire information of a real particle, the object being used as a frame of reference must interact with it. You, as a human observer, as well as an object in the natural world, must too interact with an object, from your own frame of reference, in order to experience it (i.e. observe it).
Properties of objects, thus, cannot be defined as something in themselves. Rather, they only exist in relation to other objects when they connect with them. Recall that a fundamental particle, like a photon, is not like a cannonball. You cannot track it because it does not have a definite position in and of itself. This is because its position is always relative to things it is interacting with. Take a photon with a position denoted by P that leaves a laser at point A and then arrives at a detector at point B. This is not like a cannonball whereby you could use Newtonian mechanics to trace its positions at every moment in time between point A and point B.
Rather, one should discard the notion that fundamental particles like photons even have variable properties onto themselves. They only have variable properties in relation to something else, which they are interacting with, being used as a frame of reference. In this case with the photon, P (its position) simply does not exist, but P->A exists at a moment in time (its position in relation to the laser) and P->B exists at a later moment in time (its position in relation to the detector), but P on its own simply does not exist.
In a certain sense, this is just an extension of relativity, albeit a radical one. Aristotle was first to emphasize that we only perceive relative speed. On a ship, for example, we talk of our speed relative to the ship; on land, relative to the Earth. Galileo understood that this is the reason why the Earth can move with respect to the Sun without us feeling the movement. Speed is not a property of an object on its own: it is the property of the motion of an object with respect to another object. Einstein extended the notion of relativity to time: we can say that two events are simultaneous only relatively to a given motion (see here). Quantum mechanics extends this relativity in a radical way: all variable aspects of an object exist only in relation to other objects. It is only in interactions that nature draws the world.
— Carlo Rovelli, “Reality is not what it Seems”
Indeed, this simple adjustment solves the famous Schrodinger’s cat paradox. Erwin Schrodinger had pointed out that, if one where to believe that particles can really transform themselves into waves that are a “superposition” of multiple states at once, then one could also easily imagine a simple chain reaction caused by a single particle that would result in killing a cat — or potentially not doing anything at all.
If a person is not observing the cat, and they were to make a prediction as to the cat’s state, they would have to describe the cat as a wave in Hilbert space that is a superposition of being both alive and dead simultaneously. That is, until the observer opens the box, and then suddenly, the wave would “collapse” into a dead or alive cat.
Yet, there is an obviously much simpler solution to this without positing cats at that can turn into waves. Consider the chain reaction as X, the cat as A, and the person outside the box as B. When the necessary time has ellapsed for the experiment to be complete, the cat, from its perspective, will have definitely lived or died. That is to say, the cat has interacted with what is inside the box, so X->A indeed exists . The cat is either dead or alive, but not both, from its own perspective.
However, for the person outside the box, from their point of view, the cat simply has not state at all. Why? Recall that we said systems only have states in relation to something they are interacting with. This is a definition. Thus, by definition, X->B does not exist, that is to say, the cat’s state from the person’s point of view, as they have yet to interact with the box. The cat is not a wave, but rather, categorically speaking, the cat has no state at all in relation to the person outside the box until they open the box and observe the cat’s state.
The wave function, then, serves as a tool just for making a statistical prediction of what will be observed when the person does open the box. It allows them to predict the probability the cat will be dead or alive, and thus, it allows them to predict P(X->B). It is a mistake to assume that it is meaningful to speak of the cat having an absolute state independent of frame of reference, it is only predicting the probability of what the cat’s state will be if the person were to interact with what’s inside the box.
What Born understands is that the value of Schrödinger’s ψ wave at a point in space is related to the probability of observing the electron at this point. If an atom emits an electron and is surrounded by particle detectors, the value of ψ where there is a detector determines the probability of that detector, and not another, detecting the electron. Schrödinger’s ψ is therefore not a representation of a real entity: it is an instrument of calculation that gives the probability that something real will occur. It is like the weather forecasts telling us what could happen tomorrow.
— Carlo Rovelli, “Helgoland: Making Sense of the Quantum Revolution”
The wave function is thus not an real entity, as if real waves are floating out there in Hilbert space which are perturbed whenever we try to touch them, rather, it is a tool used to make forecasts of what a particle’s state will be when we try to measure them from a particular frame of reference.
While the wave function may not be a real entity, it is still very much real in a sense. You see, not all mathematical constructs in physics need to be treated as physical entities floating around out there in the world. Some are just relationships. The famous E=mc², for example, relates energy to mass, but there is no entity that represents this floating around in the world somewhere. In a similar sense, one should think of the wave function as not an entity, but rather, something relates the context in which an interaction will take place with the probability of a system possessing certain properties during that interaction.
Thus, the wave function, in a sense, represents the context, or reference frame, in which an interaction will take place. It is akin to that of choosing a coordinate system. When the interaction does take place, the observer does not perturb what they are observing. Rather, their context changes, and thus they have to update the wave function to account for a change in their context. This update of the wave function is thus not a real physical process in the sense of perturbing a system with the observer effect and causing it to “collapse” like a house of cards, but is merely a change in the coordinate system after the context the observer finds themselves in has changed.
According to our interpretation, at the moment of measurement there is not a splitting of the world or consciousness, but a transition to this or that context in which a certain quantum correlation is already predetermined. Outside the context, a certain correlation is not predetermined, only the correlation itself is predetermined. Moving into one context or another corresponds to the choice of coordinate system (point of view); it is not a physical process. In that sense, the word “transition” isn’t exactly good. An observer simply discovers that he or she is in a certain context, within a certain point of view (in this case, unlike in classical physics, he or she cannot choose his or her context and cannot return to the original position). If the “coordinate system” is fixed, the correlated value of the physical quantity is fixed. So the quantum correlation is “coordinate”. It is coordinate both in the sense of the initial choice of the “coordinate system” and in the sense of the coordinate dependence of correlated physical quantities at a fixed choice of the initial coordinate system.
— Francois-Igor Pris, “Contextual Realism and Quantum Mechanics”
This point of view is, in a sense, not much different from the Copenhagen interpretation itself. The main distinction is that the notion of “observers” and that which is “observed” is not treated as something exclusive to conscious observers, but is merely referring to reference frames, and thus one can write down the equations for predictions from any reference frame if they wish, even that of a rock. It is, again, akin to something like velocity. It is reference frame dependent, or, in other words, context dependent, but not observer dependent. Thus, the subjectivist language can be replaced with contextual language, and the philosophical issues are largely resolved.
The founders of the theory expressed this relational character in the “observer-measurement” language. This language seems to require that special systems (the ob- server, the classical world, macroscopic objects…) escape the quantum limitations. But neither of this, and in particular no “subjective states of conscious observers”, is needed in the interpretation of QM. As soon as we relinquish this exception, and realize that any physical system can play the role of a Copenhagen’s “observer”, we fall into relational QM. Relational QM is Copenhagen quantum mechanics made democratic by bringing all systems onto the same footing.
— Carlo Rovelli, “Space is blue and birds fly through it”
Let us return to the example with the qubit carried by a particle sent from Charlie to Alice and Bob. This is similar to what Einstein, Podolsky, and Rosen had expressed concern about in their paper, and, as a result, it sometimes referred to as the EPR paradox.
There is no need to address any sort of “explanatory gap” between the wave function prior to the measurement and the qubit or particle after the measurement, as we are discarding the notion that there even is a real wave-like entity prior to the measurement. There is just what we observe, which is not observer-dependent, but context-dependent. We are, additionally, discarding the notion that our observation perturbs what is being observed as well. Alice and Bob’s qubit values are not “spontaneously created” by their act of observation (as Anton Zeilinger would phrase it), but they are merely identifying what is already there, and then updating the wave function to take into account a change in context.
Furthermore, one can even abandon the notion of superluminal action, that there is any sort of cause and effect relationship between Alice and Bob’s qubit. Recall that the states of particles — or qubits, which are carried by particles — are defined in relation to something else during an interaction. There are two qubits, one sent to Alice and Bob, which can be referred to as X and Y. There are then four unique states here, X->A, X->B, Y->A, and Y->B, where ->A and ->B are “in relation to” Alice and Bob.
When Alice receives her qubit and measures it, she comes to observe X->A. From that information, she can then update her prediction as to what Y->A would be. This “collapse of the wave function” is, again, not a physical process, but merely a change in the coordinate system after she interacts with a particle and observes her context has changed.
It has to be stressed, however, that this is merely a prediction. Again, definitionally, Y->A is defined by an interaction between that qubit (which was sent to Bob) and Alice, and so if Alice has not interacted with it yet, its value is not defined. Alice is thus merely predicting what that qubit’s value would be if she were to go and measure it. She is not, somehow, superluminally bringing Bob’s particle into existence merely because she can predict its value. She would need to locally (slower than the speed of light) travel to Bob to measure Y->A and verify her prediction is accurate.
Our interpretation allows us to explain the EPR-paradox without invoking the hypothesis of non-locality of quantum mechanics. The «cause» (in a generalised sense) of quantum correlations is the entangled wave function. The correlated quantum events are not autonomous, but they are determined in the context of their observation. Independently from the means of their identification, there are no events. The reduction of a wave function in the «process of measurement» is not a real physical process, requiring an explanation, but a move to a context of measurement of a concrete value of a physical quantity. Respectively, the measurement is not a physical interaction leading to a change in the state of a system, but the identification of a contextual physical reality. That is, in a sense, in measuring (always in a context), one identifies just the fragment of reality where the (quantum) correlation takes place. As the elements of reality, the correlated events do not arise; they are. Only their identifications do arise.
— Francois Igor Pris, “The Real Meaning of Quantum Mechanics”
There is thus no wave function collapse, no measurement problem, and no nonlocality, not even the appearance of nonlocality. The so-called “spooky action at a distance” disappears, and so does all the confusion regarding measurement and wave function collapse.
There is, however, one last consideration, and this point is probably the most difficult to swallow. We have a very intuitive notion that “objective reality” refers to some sort of cosmic observer, some sort of superbeing that can see everything at once. Even in the diagrams I drew, I drew them such that Charlie, Alice, and Bob were all in the same image, so we can talk about the perspectives all at once.
When imagining what objective reality is really like, we tend to imagine in our heads some sort of third-person, godlike, or aerial point of view that can look down on everything at once, or maybe a being which can shift its perspective to anywhere in the world simultaneously. This is a notion we have to abandon. While it is intuitive, it simply makes no sense. The third-person point of view is still the view of a person. Nothing about it would be more “objective” than any other point of view. There is no preferred reference frame in nature, all reference dames are on equal footing.
Equally, such a cosmic superbeing obviously does not exist. It is not physically possible to occupy a perspective that can see everything simultaneously — as information cannot travel faster than the speed of light — or to shift one’s perspective faster than the speed of light. This metaphysical conception of what objective reality entails, thus, is a fallacious one we have to abandon. That is not to say that we should abandon the notion of objective reality, but rather, we should come to acknowledge that what constitutes objective reality is not some sort of “external” preferred reference frame that “looks down” upon reality, but the totality of all possible reference frames from the inside.
If we imagine the totality of things, we are imagining being outside the universe, looking at it from out there. But there is no “outside” to the totality of things. The external point of view is a point of view that does not exist. Every description of the world is from inside it. The externally observed world does not exist; what exists are only internal perspectives on the world which are partial and reflect one another. The world is this reciprocal reflection of perspectives.
— Carlo Rovelli, “Helgoland: Making Sense of the Quantum Revolution”
Recall that, if Alice, from her frame of reference, measures X->A, she can update her prediction for Y->A. If, let’s say, she measures X->A to be 0, as shown in the diagram, she can be certain if she were to measure Y->A in the future, it would be 1. This tells us nothing about X->B and Y->B, and, at first, seems to lead to a contradiction.
You see, prior to Alice measuring X->A, she could only make a probabilistic prediction Y->A where P(Y->A) is 50% for 0 and 50% for 1. After she measures X->A, she can then update her prediction for Y->A so that it is a 100% chance of being a 1. However, for Bob, from his perspective, he has not yet measured his qubit, so, for him, he would state that P(Y->B) is 50% for 0 and 50% for 1, even though for Alice Y->A is definitely a 1.
This seems to imply that there is a 50% probability that Bob could measure his qubit to have a value of 0, yet Alice would predict her measurement of Bob’s particle to have a value of 1, thus leading to a contradiction.
However, in practice, this can never actually occur. Why? Because Alice can only ever see from Alice’s point of view. She can never occupy Bob’s frame of reference. Bob, likewise, could never occupy Alice’s frame of reference. In this thought experiment, we are imagining ourselves shifting around frames of reference, looking at what Alice does from her reference frame and then shifting to Bob and asking what Bob would see in that moment.
This is exactly what is meant by the godlike cosmic superbeing. Such a thing cannot be done in reality, even though it seems intuitive to talk about it this way. If we posit such a godlike superbeing, we indeed run into seeming contradictions when comparing two reference frames. However, these seeming contradictions disappear if we simply trace out the reference frames separately and so not try to unify them under some sort of cosmic observer.
Observer A can of course measure the state of B…but only when A is back into causal contact with B. This is, needless to say, in the future light-cone of A, and therefore poses no challenge for locality. In other words, Einstein’s reasoning requires the existence of a hypothetical super-observer that can instantaneously measure the state of A and B. It is the hypothetical existence of such nonlocal super-being, and not QM, that violates locality.
— Carlo Rovelli et al, “Relational EPR”
Objective reality should not be thought of as some sort of preferred reference frame adopted by a superobserver. Rather, it should be thought of as the totality of fragmented reference frames. Within each reference frame independently, the laws of physics are perfectly consistent, perfectly local, and no one will ever observe an inconsistency. The apparent inconsistency, the apparent nonlocality, only arises when the metaphysical construct of a superobserver is added to the picture.
Our position can be seen as a contextual reinterpretation (or even correction) of Kit Fine’s “fragmentalism” position…In contrast to Fine, we believe, however, that what we have in common in this example is not ontology, but fragments of reality, in particular unconceptualized “events”. Ontology — what really exists — depends on context…Physical quantities have different values in different reference systems (contexts), but there is a connection between their values in different reference systems. At the same time, the measurement results in the actualization of a point of view. In this sense, quantum reality turns out to be “fragmented”, or, more precisely, contextualized.
— Francois Igor Pris, “Contextual Realism and Quantum Mechanics”
One might worry that if reference frames are, in a sense, fragmented, and not reconcilable under a preferred reference frame, then observers might run into contradictions, i.e. they may disagree as to what constitutes objective reality. It turns, however, this is not the case. As previously stated, the rules of quantum theory guarantee internal consistency in all reference frames. When observers share their measurement results, they will come to agree on what is objectively real.
The only disagreement they run into is, in a sense, when a particle’s state actually acquired being, as, this depends upon what both parties have interacted with from their differing points of view. However, this is not a fundamental disagreement, it is comparable to disagreements over the velocity of an object. While two observers may disagree over the velocity, the confusion disappears when they take into account they occupy different frames of reference.
In a similar sense, two observers may disagree over when a particle’s property came into being, but when they acknowledge that this is just because they occupy different frames of reference, the seeming disagreement is reconciled. Indeed, even though they will disagree as to when the particle’s property came into being, they will not disagree — if they were to communicate their results together — what that particle’s property actually is.
There is method in this madness. If I know that you have looked at the butterfly’s wings, and you tell me that they were blue, I know that if I look at them I will see them as blue: this is what the theory predicts, despite the fact that properties are relative. The fragmentation of points of view, the multiplicity of perspectives opened up by the fact that properties are only relative, is repaired, made coherent, by this consistency, which is an intrinsic part of the grammar of the theory. This consistency is the basis of the intersubjectivity that grounds the objectivity of our communal vision of the world. The wings of the butterfly will always be the same color for all of us.
— Carlo Rovelli, “Helgoland: Making Sense of the Quantum Revolution”
