Why the Basis of Reality Is Not in Interactions: Observation Can’t Be Replaced With Interaction
A Constructive Critique on Carlo Rovelli’s Philosophy of Weak Realism
One of the most interesting contemporary thinkers is Carlo Rovelli. Rovelli’s relational interpretation of reality, which he has referred to as weak realism, is overall a very intriguing and in many ways convincing view of reality. Rovelli views reality as reducible not to autonomous objects with properties fully localizable to themselves, but instead only reducible to interactions. This means that objects only exist relative to something else in the moment of interaction.
From this perspective, Rovelli is able to dissolve much of the “weirdness” of quantum theory. No longer do you have to speak of “spooky action at a distance,” cats that are simultaneously alive and dead, some fundamental role for measuring devices, so on and so forth. You get a picture of reality that is both compatible with quantum theory and avoids positing the majority of these incomprehensible ideas, giving you an overall rather simple and easy to grasp understanding of reality.
The basis of this worldview is not entirely original to Rovelli. Erwin Schrödinger had written something similar, pointing out that in quantum mechanics, it is only possible under certain conditions to actually reconstruct the properties of a particle in between interactions, while in other situations, such a reconstruction is impossible. Schrödinger thus concluded that we should abandon the notion that particles really exist as autonomous entities that always have a continuous existence in between interactions. In own his words, we should abandon the notion that independent of what they are interacting with, that the particle “must have come from somewhere, it must have been somewhere” but instead “regard a particle not as a permanent entity but as an instantaneous event.”
[W]e are so used to thinking that at every moment between the two observations the first particle must have been somewhere, it must have followed a path, whether we know it or not. And similarly the second particle must have come from somewhere, it must have been somewhere at the moment of our first observation…This habit of thought we must dismiss. We must not admit the possibility of continuous observation. Observations are to be regarded as discrete, disconnected events. Between them there are gaps which we cannot fill in. There are cases where we should upset everything if we admitted the possibility of continuous observation. That is why I said it is better to regard a particle not as a permanent entity but as an instantaneous event. Sometimes these events form chains that give the illusion of permanent beings — but only in particular circumstances and only for an extremely short period of time in every single case…The gaps, eliminated from the wave picture, have withdrawn to the connection between the wave picture and the observable facts. The latter are not in one-to-one correspondence with the former.…We must, so it seems, give up the idea of tracing back to the source the history of a particle that manifests itself on the plate…We cannot tell where the particle was before it hit the plate. We cannot tell through which opening it has come. This is one of the typical gaps in the description of observable events, and very characteristic of the lack of individuality in the particle.
— Erwin Schrödinger, “Nature and the Greeks and Science and Humanism”
There is a particular issue I have with the notion that reality is reducible to “interactions,” and it is probably not the criticism you have heard before. Most criticisms of Rovelli come from a more antagonist point of view, from someone who rejects his weak realism because they wish to uphold classical metaphysical realism. I have written articles before criticizing metaphysical realism, so I am not in this camp. The purpose of this critique is not to dismiss Rovelli’s views, but to improve upon them. If you are curious of my criticisms of metaphysical realism, you can check out the article below.
“Interaction” is a Party of Three
If the universe is relational, as Rovelli argues, then no system can have properties in isolation. It can only have properties in relation to something else. This relation implies that the simplest unit of reality is the relation between two physical systems, which I will sometimes here interchangeably refer to as objects. If you subtract one of those two systems, you would not have a relation anymore, but a single object in isolation, which is taken as not meaningful in relational quantum mechanics. Hence, an interaction between two systems is as simple as you can get.
Yet, counterintuitively, the term “interaction” implicitly entails a party of three objects, not two, and therefore cannot be the simplest unit of reality.
This may seem a bit strange, how can an interaction imply three? If I see two billiard balls slam into each other, that is clearly an interaction involving only two objects. Here’s the kicker, there is implicitly an object you are leaving out: you! When you say, “I see two billiard balls,” how do you see that? The billiard balls must interact with you. In order to perceive two billiard balls interacting, the two interacting balls must also interact with you in some way. Indeed, in order for you to perceive any two systems interacting, those two systems must somehow also then interact with you, a third system.
This is a party of three, not two.
Indeed, you might say, “what if I’m not in the room? I can still conceive of the two billiard balls colliding on their own.”
A person blind since birth cannot even see in their dreams, although a person blind much after birth can sometimes still dream with sight. I have never seen a pink elephant, but I have seen pink things and elephants, so I can remix them in mind and imagine a pink elephant. However, I cannot conceive of an elephant that is a color I have never seen before.
Why do I say all this? To illustrate that what we conceive of in our imagination is ultimately limited to what we have perceived before, it is ultimately just remixes of all our past experiences. If we are only remixing our past observation, and all observations entail an interaction between us and the system we are observing, then any time we conceive of something, we are also always implicitly conceiving of ourselves interacting with it.
Even if you try to conceive of an asteroid floating around in empty space with nothing around it, to form of picture of it in your mind still requires you to imagine what it would look like if you were there to look at it. For example, the picture in your mind is not pure black, then this implies light is reflecting off of into your retina. You cannot conceive of what it would be like in perfect isolation, because to do so would be to conceive of nothing at all, because there would be nothing to see!
Any attempt to conceive of two objects interacting thus ultimately, implicitly, is conceiving of a system of three objects interacting. In order to actually reduce nature to a relation between two objects only, we thus need to use language different from “interaction.”
Interactions have a Symmetry to Them
Consider two billiard balls moving towards each other in empty space such that they collide off of each other. Due to Newton’s third law, every action has an equal and opposite reaction. If the interaction is elastic, they would just bounce off of each other, resulting in the motion of both of the billiard balls changing.
In order to describe both billiard balls as moving in this interaction, their position must be different from the number zero and must be capable of changing over time. Of course, if their position was always zero, they would not move anywhere. Yet, if one of these balls was used as the basis of our coordinate system, then the origin would indeed be zero, and so it should not be depicted as moving. Since the ball would define the origin, then if you moved the ball, the origin would move, and so it would be impossible for its position to ever be anything but zero.
The fact that we are depicting both balls moving thus suggests an outside, third-person perspective, because neither of the balls are at the origin. They are all moving relative to a third object viewed under a third perspective.
Indeed, velocity is a property that doesn’t actually make much sense to apply to oneself from one’s own perspective. The velocity of yourself is always zero. You are always at rest relative to yourself. It is always everything around you that is moving. If you get in a moving car, from your perspective you are the one still, and it is the earth moving backwards underneath you.
Hence, depicting the symmetrical interaction above implies it is being perceived from a perspective that is different from either of the two objects involved in the interaction. It is being depicted from, again, a third-person, “outside” point of view. A third-person implies, well, a third party.
If we were to change this such that one of the billiard balls is the basis of the coordinate system, which we will refer to as the referent ball, then that referent ball would never move with respect to itself. The other billiard ball would slam into it and bounce off of it, but the referent ball would not have its velocity changed because it was never moving and can never move. Only the ball that smacked into it would have its velocity changed.
Notice something that happens when we choose one of the objects in the interaction as the basis of the coordinate system: the interaction is no longer symmetrical. The referent object is not doing anything at all, it is not being “affected.” Only those objects that are not the referent object are actually being altered.
You might say, if there’s a planet nearby, the floating billiard ball in space could tell its trajectory changed by comparing itself to the planet. However, from its “perspective,” what it would “see” if it somehow was sentient, would be that after the collision with the other billiard ball, the result of that collision would change the velocity of both the ball that collided with it and the planet. What it would actually “perceive” directly is the planet’s velocity change, not its own. It could say that its velocity changed relative to the planet, but not relative to itself.
Contextuality is Asymmetrical
Let’s say, we have two objects that interact as seen from a third-person point of view. Now, let’s consider that same interaction but without the third-person, as perceived by one of the objects participating in it. This effectively requires choosing one object as the basis of the coordinate system from which to describe the other object from, which is just a reference frame.
As shown in the previous section, a reference frame has an inherent asymmetry to it that is not there when considering the interaction from a third-person perspective. Only one object is actually “perceived” to change, while the referent object does not change. Choosing a coordinate system is arbitrary precisely because the interaction is symmetrical. There is a symmetry in the fact that we can equally choose either of the two participants in the interaction as the basis of the coordinate system, but the moment we choose one, immediately, the symmetry is broken.
Leaving the third-person point of view and entering the first-person point of view introduces a kind of asymmetry that is forgotten when we speak merely of “interaction.” The simplest unit of reality is not symmetrical interactions, but very much asymmetrical reference frames.
This is the main difference between Rovelli’s weak realism and Jocelyn Benoist’s contextual realism. By focusing on “interaction,” which implicitly involves three parties, Rovelli’s philosophy ultimately places the third-person perspective at the basis of reality. Contextual realism, instead, places the first-person perspective at the basis of the reality.
This is because contextual realism is a direct realist philosophy and maintains committed to the notion that we perceive reality directly as it really is. Clearly, we experience reality from a first-person point of view, so for this to be the case, then material reality itself must be first-person. Both contextual realism and weak realism deny that the “cosmic” perspective upheld in metaphysical realist philosophy even exists.
Rovelli says that “observation” can be replaced with “interaction,” but clearly, when we observe something, there is an unambiguous distinction between the observer (ourselves) and the observed (what we “see”). That is to say, the relationship between the two objects is asymmetrical. Yet, by just saying “interaction,” there is ambiguity between what is the observer and what is the observed. This is the kind of symmetry that is the issue here.
Contextual realism is not an idealist philosophy, so it agrees that this “observation” can occur between any two objects. However, what we usually refer to as the “observer-observed” relationship is still something indispensable, even when speaking of individual particles.
[T]he observer and the observed system can change their statuses. An observer can become what is observed. And vice versa. In this sense, all physical systems are on the par, and there is no privileged observer.
However, at the same time, — and this is what Rovelli does not take into account — once in a context an observer and an observed system are determined, there always is a categorical difference between them.
— Francois-Igor Pris, “The Real Meaning of Quantum Mechanics”
Sure, it seems kind of silly to call a single photon an “observer,” but that is just a limitation in language. We currently do not have the language to describe this “observer-observed” relation in a way that is not anthropomorphic.
The photon lacks a brain and thus has no cognitive behaviors, and thus it cannot reflect upon and describe what reality is like from its own context. That does not mean, however, that there is no reality from such a context. We can clearly write down the mathematical description of what such a perspective would be like, and so if we believe our mathematical theories, we have to believe that there is meaningfully a reality from the reference frame of the photon.
Of course, you may point out, the quantitative mathematical description differs from the qualitative experience. Yes, that is true, but also trivial. This is simply the distinction between a description of a thing and that thing in reality. Describing the Eiffel Tower will never substitute for experiencing the real thing in the real world. There is not a “gulf” between description and reality as if there is “distance” between the two. They are categorically different. No matter how detailed a description is, it will never become the real thing, as if a piece of paper containing a sufficiently accurate description of fire will suddenly burst into flames.
Our mathematical models allow us to describe reality from any possible context, but there will always be a categorical difference between what it is like to be in that reference frame, that is to say, how that reference frame is actually realized in material reality, and a mere description of it.
Observation as Distinct from Interaction
In our day-to-day lives, we do not typically think of most of our perceptions as interactions, even though logically we know they are. For example, if we see a cup, our first intuition is not to think that they are light rays bouncing off of the cup and interacting with our retina and thus our brain. We just think, “there is a cup over there.” The object is thought of in and of itself, without including ourselves into the picture.
We are capable of doing this for the same reason that when we chose one of the billiard balls as the basis of you frame of reference, then the interaction became asymmetrical: the billiard ball that was chosen as the basis of the reference frame was not perturbed by the interaction itself. If we stick to a purely first-person perspective, then the world around us is always what is perturbed, and never ourselves. Indeed, ourselves as an object never even would enter the picture.
However, sticking to a purely first-person perspective is also not particularly intuitive, as there are plenty of times where we also do consider things in terms of interactions. For example, we can directly see our hands in front of our face. When we touch something, we can perceive our hand interacting with that object because the collective system of the hand and the object interact with our retinas, i.e. it is a third-person perspective. We do not see our own eyeballs, but we do see things external to our eyeballs, such as our hands. There is, additionally, categorical distinction between seeing our hands interacting with an object, and the experience of our hands touching the object.
Unlike vision on its own, touch tends to be intuitive to conceive of both in the third-person and in the first-person. I am unsure if this would change for a blind person who does not simultaneously see and feel what they touch, however, at least in my experience as a sighted person, it is much more intuitive to conceive of touch as indeed an interaction, from the third-person. Oddly, I find myself associating touch less with the actual feeling of it but even more so with the sight of it. If someone told me to imagine myself petting an elephant, I would probably imagine myself from the third-person petting the elephant rather than imagining the feeling and texture of the elephant’s skin.
In some cases, we find it intuitive to consider ourselves from the third-person as interacting with something, while in other cases, we find it intuitive to just consider the thing we observe as it is, without including ourselves into the picture. This makes it intuitive for us to treat interaction and observation as precisely equivalent. This equivalency then makes us confuse the two together, such as concluding that interaction can only involve two parties, or that an observation includes the observer in the picture. When we put a clear delineation between these perspectives, we find that including the observer in the picture is only possible when discussing an interaction, and an interaction involves three parties and not two.
I am reminded of something analogous in Adam Smith’s The Wealth of Nations. He discusses how various social classes can have revenue streams from various sources simultaneously, such as a person who makes profits from hired labor, as well as collects rent from leased land, as well as collects wages as he is also employed and earns a salary. Typically, a person like this would not have three separate banking accounts for these sources. The sources of wealth would all accumulate in the same basket, so to speak, and all be seen side-by-side.
Smith pointed out that the fact they are all seen simultaneously, side-by-side, causes people to confuse them together. They fail to delineate between them, to recognize that the person’s revenue stream actually comes from various different social processes that are governed by different socioeconomic laws, and instead treat them all as a single basket of “profits.”
Similarly, the fact that some of our senses, like touch, can be both simultaneously experienced in the first-person and third-person, makes us often fail to properly delineate between these perspectives.
Clearly delineating between these perspectives actually turns the conventional wisdom on its head. Typically, we think of describing something from the third-person as describing reality “as it really is,” and describing something from the first-person as describing some sort of “subjective experience.” Yet, from this perspective, describing something from the first-person is reality as it really is, and the third-person is a layer of abstraction upwards.
It is precisely when we describe things purely in the first-person that we are excluding ourselves from the picture and thus describing the system as it really is, on its own. For example, if I describe, from the first-person, a tree, I am just going to be describing the tree, all of its properties that I observe. Someone from the third-person might see me and the tree together, and thus describe how the tree interacts with me to lead to me describing it the way I do. If we wish to describe the tree on its own, without any other object in the picture, this is only feasible from a first-person perspective.
Indeed, even calling it the “observer-observed” relation is ultimately describing it from the third-person perspective as a kind of interaction. When one truly adopts a first-person perspective, they only describe the “observed,” not the observer. It is only from such a perspective that it is possible to describe the objects themselves.
Consider, for example, if you were born into a universe without mirrors so you could never see yourself. Furthermore, your body did not allow for you to ever place parts of it in front of your face. In such a universe, you could never perceive yourself through reflection. Would you even, then, develop a notion of the “self” at all as a distinct object in the world? Such a thing is so alien to us that many of us would say we still would, because we have difficulty conceiving of entirely different ways of being.
If we were raised on a different planet, with different biology, we would likely carve up the world in our minds very differently. Consider a cat, for example. It is not feasible to actually come up with a rigorous definition of where the cat actually “begins” and where it “ends” both in space and in time. When it breathes in air from its surroundings, at what precise point, without any ambiguity, does that air cease to be part of its surroundings and become part of the cat? When the cat is born and when it dies, at what precise point, without any ambiguity, do these moments occur?
An alien species with a very different biology may thus find the way we carve up the world into “cats” and “trees” very arbitrary. The aliens would also have their own way of carving up the world, and it too may look equally as alien and difficult to grasp.
We tend to have a bias towards our way of interpreting the world such that we view it as inherently inevitable such that we cannot even conceive of just how drastically different things could be. While it may feel incredulous to you, as you find conceiving of yourself as a distinct object as one of the most intuitive things there is, I do find it to be rather likely that, under the right material conditions, an intelligent being could carve up the world in a way that does not include itself within it.
The self requires reflection, it requires some way to perceive one’s own body. It can be a reflection in the colloquial sense such as looking in the mirror and seeing oneself, or it can be reflection in some other sense. To look at your own hand is still a reflection: it requires light reflecting off of your body into your retina. If there was no way at all to perceive oneself, then it is hard to imagine how or why a being in that universe would develop as concept of themselves as a distinct object. Such a concept would play no role and have no predictive power in their lives.
This is why I frequently criticize Descartes’ famous phrase “I think, therefore I am.” I can see an argument to be made that thought implies being, however, both the premise and the conclude here contain I equally: “I therefore I.” This is often justified by saying that the self is self-evident and undeniable. However, I am not convinced of this notion.
Our notion of the self is derived from reflection, and reflections must be observed. The very fact that we can conceive of a being that observes the world differently from us yet does not develop a notion of the self demonstrates that the notion of the self is something derived from observation of the world. It is a posteriori and not a priori.
As bizarre as it may sound, the self does not actually exist in the first-person perspective, only a reflection of the self does, which is an object that can only be viewed externally. The self can only be derived as a concept if we are capable of perceiving our own reflection, but the reflection of an object is not equivalent to that object. We like to think we can perceive ourselves because of reflection, but ultimately we are perceiving a very good substitute for ourselves.
Here is basically the point, summarized: If we have a universe that actually only contains two objects, then it would be impossible to ever describe an interaction occurring in such a universe. We would have to pick one of those objects as the basis of our coordinate system to describe the rest of the universe from, but the “rest of the universe” would just include one other object. Hence, a universe with two objects could only ever actually be described as containing one object, although the object would differ depending upon the reference frame chosen.
The only way to actually conceive of that universe genuinely containing two objects would be to describe them under a third reference frame, but that implies a third object, and thus contradicts ourselves. This is why we find it so intuitive to believe that the universe is really made up of objects in themselves, because what is described as an “interaction” from a third-person perspective, in a first-person perspective simply contains the other object on its own.
A universe containing only two objects would thus really only be describable in terms of those two objects on their own, separately. That universe would not really be composed of two objects side-by-side but two “fragmented” realities where in one, one of the two objects exists, and in the other, the other object exists, but in neither fragments of reality do both objects exist simultaneously. We also cannot juxtapose these fragments, considering them simultaneously side-by-side, because to do so implies the existence of a third object and contradicts our premises. Rovelli, too, says something similar.
In other words, RQM is not the claim that reality is described by the collection of all properties relative to all systems. This collection is assumed not to make sense. Rather, reality admits one description per (observing) system, each being internally consistent.
— Carlo Rovelli & Matteo Smerlak, “Relational EPR”
A first-person perspective is thus inherently asymmetrical in the sense that one of the two objects suddenly leaves the picture. The whole “observer-observed” relation is just an anthropomorphic way of describing this asymmetrical perspective, which is inherent to any relational/relativistic theory.
Most terms we use in the English language to capture this are rather anthropomorphic. It is described as a “first-person point of view,” for example. To invoke a “person” is to anthropomorphize it. It is better to instead refer to it with something that does not imply human characteristics. For now, we will just refer to it as contextualism or contextuality.
Implications for Quantum Theory
It is important to remove the anthropomorphic character of these terms because the attempt to anthropomorphize them is what leads to so much philosophical confusion. The whole philosophy of idealism, for example, stems around trying to assign labels to contextualism that have an anthropomorphic character, such as “mind,” or “consciousness,” or the “first-person point of view,” or “subjective experience.” The terms all imply some sort of inherent connection between this point of view and what makes us human, and thus makes it seem as if humans possess something unique. By adopting a different term, such as describing material reality as contextual, it becomes clear that this is a property of physical reality and not a property special to humans. It has nothing to do with the mind, subjects, or conscious agents at all.
The material sciences are driven solely by observation. Everything we know, we know it because we conducted an experiment and observed the results. No finding is accepted by the scientific community unless the same experiment can be replicated by others who can also observe the results. The whole point of scientific theories is to both explain what we observe, as well as to predict what we will observe in the future based on observations from the present and past.
The material sciences do not describe some invisible reality that is entirely independent of perceptual experience. The material sciences describe precisely what we experience. They are the study of the reality you find yourself immersed in every day, the reality that surrounds you at all times. Not something distant and alien, or, at worst, entirely unreachable. A contextual realist perspective allows for us to close this supposed gap between the material sciences and what we observe, as reality is taken to be precisely equivalent to what we observe, and the material sciences based on observation.
All scientific theories that are dependent upon reference frame allow you to describe reality from any arbitrary coordinate system, that is to say, they are all contextual. A description of reality is not equivalent to reality itself. Reality is what we observe it to be, and thus observation is a real event. We need to have a distinction between the actual ontological status of the system, which is tied to a real observation and is qualitative, and a description of the system, which is not necessarily tied to a real observation and is quantitative. A description of the Eiffel Tower, again, is very different than actually observing the real Eiffel Tower in the real world, as it really is.
(I say “not necessarily” as a description can sometimes implicitly reference a real qualitative experience, such as, if I say “that cat we saw yesterday” rather than merely describing the cat in the abstract.)
When you “describe” a system using a state vector (sometimes the state vector is also referred to as the “wave function” even though they are technically different things), you are not actually describing anything that exists. You are predicting the outcome of a future observation. In a third-person description, we would say that these observations are just you interacting with the system.
However, “interaction” again implies a kind of symmetry, and we know quantum theory is not symmetrical. When you make an observation, there is a sudden “leap” from a description of a linearly evolving unitary state to a nonlinear determinate outcome. This “leap” also only occurs from the reference frame of the person partaking in the interaction.
A person on the outside would still describe it evolving linearly according to the Schrödinger equation, that is to say, the symmetry still exists for a person who observes the interaction, but not for the person to participate in it. Indeed, the person on the outside would describe the observer as entangled with what they are observing in a very symmetrical way where the two are perfectly correlated with one another.
What quantum mechanics ultimately does is predict the outcome of those interactions but not as an “interaction” but from a more fundamental perspective, from the contextual perspective, i.e. from the reference frame of one of those systems that are part of the interaction.
Within the framework of contextualism, objects do not “interact” with the observer as the observer is not part of the picture. Rather, objects merely enter into reality or disappear from reality from this given point of view, i.e. objects do not “interact” with the observer but are instead realized from the observer’s frame of reference. Hence, what the state vector represents is a prediction as to what properties of a system will be realized under a contextual perspective.
There is no “measurement problem” at all, as there is no fundamental role for measuring devices. The fundamental role is given to realization of systems under a contextual perspective, meaning that any arbitrary system can be chosen as the basis of the coordinate system in order to describe reality, and in any arbitrary coordinate system, properties of systems will or will not be realized according to that system’s context.
All potential ways of slicing up reality into different contextual perspectives are treated as equally real. Although, juxtaposing any two perspectives simultaneously is treated as not real as such a thing implies an “absolute” and non-contextual perspective that could perceive reality from multiple perspectives simultaneously, and would thus be context-independent. To simultaneously juxtapose reference frames is to abandon contextualism.
Since the behavior of fundamental particles is fundamentally random, the best you can do is a statistical prediction of what properties of the system will be realized under a particular context. You cannot know with certainty ahead of time. What you observe also implies a particular context. For example, if you see a train traveling at 150 km/h, then hop in a car at 50 km/h, you would see it then only traveling at 100 km/h. Assume that somehow you could not see any reflections of yourself or even the car, but only the train. If you were randomly placed in either inside of the car or not in the car, you could tell which context you are in solely from the perceived velocity of the train. If you perceive the train to slow down, you know you left the car, even if you cannot perceive the car or yourself.
This is what ultimately differs between traditional notions of relativity and contextualism. Traditional notions of relativity imagine the person’s reference frame depends upon where they exist in reality, so it is inherently conceived of in the third-person. When we said the person got in the car to accelerate to a new reference frame, we are conceiving of the person getting in the car. However, as said before, a consistently first-person description would not include the person themselves. The context is thus determined not by the person’s own properties, but the properties of everything else that is perceived and perceivable.
If the context is determined by everything else, then what we perceived and what is perceivable determines our context. If the outcome of experiments in quantum mechanics is random, then what we perceive is not determined beforehand. If we combine these two ideas together, what we find is that unlike in Galilean relativity, in quantum mechanics, our context can change in ways that are outside of our own control and is unpredictable.
The reduction of the state vector — which is sometimes misleadingly called the collapse of the wave function — does not “cause” us to perceive what we perceive. What we perceive is just reality as it exists under that particular context, i.e. what we perceive is reality as it has been realized under that particular context. As a consequence, the context which we exist within is altered, and so we have to adjust the state vector accordingly.
It is comparable to the taring of a scale. Scales measure weight and mass relative to some coordinate system. If you want to measure the weight of an object without the beaker included, you can tare the scale which centers the coordinate system on the beaker, and thus the beaker is excluded from the picture. If you change beakers, you have to change the coordinate system by taring the scale a second time.
Due to the fact that a particular outcome being realized implies a change in context, and that quantum mechanics is a contextual theory, this means you need to adjust the state vector in response to perceiving certain outcomes being realized.
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”
Indeed, if we introduce a third-person perspective, this also makes sense, because the interaction of the particle with the observer is symmetrical, so the observer themselves is affected.
How is it that you could “know” the electron is in a spin up state unless the electron affected your measuring device, which in turn affects your sensory organs, which in turn sends electrical signals to your brain, which are all correlated together? There must be a correlation between your brain state and what you “know” in order for it to be genuine knowledge at all.
From the “outside” point of view, you are physically altered by the interaction, and so if you are being used as the basis of the coordinate system, well, you have changed, so this would ultimately demand the adoption of a new coordinate system as you are no longer the same object you once were.
You can choose any physical system to describe reality by. We typically think of the photon detector as the “observer” and the photon as what is “observed,” yet the mathematics of quantum theory actually allows you to treat the photon as the “observer” and the photon detector as what is “observed.” You do not run into any contradictions if you do this.
The founders of the theory expressed this relational character in the “observer-measurement” language. This language seems to require that special systems (the observer, 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, “The Sky is Blue and Birds Fly Through It”
While you may end up with two different descriptions of what is going on from both perspectives, they are reconcilable with each other. It is, again, akin to how Galilean relativity, two different observers may describe the velocity of the same object to be different, but it doesn’t lead to “confusion.” The theory itself includes the fact that reality may be described in different contexts, from different perspectives, and thus the theory itself predicts these disagreements and explains them. These disagreements thus do not amount to the theory failing, they are not a “contradiction,” but entirely what is predicted and expected.
While Carlo Rovelli would replace the word “observation” or “measurement” with “interaction,” the word “interaction” does not quite capture what quantum theory is actually predicting. From a third-person perspective, two objects interacting does not actually lead to a reduction of the state vector, it does not lead to a realization of a particular outcome. You still have to describe Schrödinger’s cat in a superposition of states entangled with the particle inside of the box. The outcome is only realized in a contextual perspective. From the cat’s point of view, there is a realized outcome. From the outside human’s point of view, there is not yet a definite outcome until they open the box, and then a particular outcome is realized.
Hence, from a contextual worldview, you cannot replace “observation” with “interaction,” as observation implies a kind of asymmetry inherent to contextualism, while interaction does not. We have to keep in mind the categorical distinction between what is the “observer” and what is “observed.” Sadly, we do not have commonly adopted words to describe this in a way that is not anthropomorphic, so people incorrectly think that stressing the importance of this asymmetry implies a kind of idealism, as “observers” are associated with conscious agents.
It may help to adopt different language to avoid this problem. For example, to refer to the “observer” as the referent object, which is what is implicitly being referred to whenever a coordinate system is used, as the basis of that coordinate system. The “observed” can then be described as simply what is contextually realized from that reference system. If you have better suggestions, leave it in the comments.
There is no Observer Effect
The only way for one object to alter another is for it to interact with it. However, interaction, again, is only a property observable under a third-person perspective, and quantum theory predicts instead what will be realized under a contextual perspective. We thus cannot conclude that the act of observation actually alters the state of the system because there is no interaction occurring, only the identification of a system as it has been contextually realized in the real world.
I have already went into detail in this in the article below on why you cannot actually establish the existence of an observer effect from something like the double-slit experiment, so I will not repeat myself too much here. While you can establish a correlation between different measurement settings and different outcomes, this is not sufficient to establish that you actively perturb the system you are measuring. You can also show a correlation between the different measurement settings of a train’s velocity while sitting on the ground or riding alongside it in a car. This does not prove hopping into a car actively perturbs the train and slows down its velocity.
From a contextual realist perspective, we do not actually perturb systems that we are observing, but what we observe does depend upon the context of that observation. Hence, different measurement settings will produce different results. Interpretations like QBism that suggest the observer and the system collectively work together to create reality “in participation” only make sense if you are juxtaposing the observer and the system together, which in turn only makes sense if conceived of from a third-person perspective. From a contextual realist perspective, you are neither altering nor creating reality by observing it. You are just observing reality as it exists, but what exists depends upon the context of that observation.
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”
