A century has passed since the discovery of quantum mechanics, the most successful theory in the history of science, and physicists haven’t yet reached a consensus about its meaning. What does quantum mechanics tell us about the nature of reality? Physicists haven’t been able to come up with an uncontroversial answer.
The reason for this impasse is clear: physicists have been working on the wrong assumptions about the world we observe. In other words: it’s time for a paradigm shift.
The good news is, the new paradigm that will usher the new Copernican Revolution in our understanding of the natural world is ridiculously simple, and doesn’t require a familiarity with advanced mathematics, or the acceptance of weird counter-intuitive notions. It can be described in a few plain words that anyone can understand.
So here it is. I present to you the sensorial view.
The nature of the physical world
According to the sensorial view, the physical world isn’t made of self-existing objects or “things”. It isn’t made of atoms, or subatomic particles, or quantum fields. The physical world is made of qualia. More precisely: it’s made of sensations.
This is such an obvious fact that spelling it out feels like uttering the most ridiculous platitude. And yet, few people seem able to grasp this simple truth. The physical world is the world we see, hear, smell, taste, touch. That’s what it is, and nothing more.
What I’m saying is this: the physical world is not the world we think about. The physical world doesn’t exist in our minds. It only exists in our sensations. The world we think about is only a model, a mental representation of the real thing.
This is sensorialism: a distinct metaphysical view that transcends the age-long debate between idealism and materialism. In the sensorial view, the physical world is not a creation of the mind, be it the individual mind or some hypothetical “universal consciousness”. But neither does the physical world exist “out there”, by itself. We humans, along with all other living organisms, are unwittingly creating it as we interact with it: as we touch it, see it, hear and smell and taste it. In short, as we sense it.
Sharing the world
The simplicity and beauty of sensorialism is that it doesn’t rely on some abstract, ill-defined concept of “consciousness”. And at the same time, it gets rid of any unnecessary additions to our actual experience of the world, like the old notion of “matter”.
The traditional belief in a physical world made of “matter”, a hypothetical self-existing substance independent from our observation, is well rooted in everyday experience. It provides a straightforward explanation to a basic fact of life: we all (not just humans, but all living beings) observe and share the same physical world.
It is just a belief, nonetheless. The more we know about the fundamental nature of physical reality, the more elusive this hypothetical “matter” seems to be. Quantum mechanics has shown that there is an unavoidable link between physical reality and our observation of it. And yet, few scientists are ready to let go of the notion of objective matter independent from observation. To use Einstein’s famous phrase, it seems absurd to think that the moon exists only when we are looking at it.
Einstein’s intuition was quite correct, as was often the case. But there is another way to explicate that intuition, without the need of postulating the existence of “unobserved matter”, a conjectural substrate that is by definition unobservable. That alternative way of explaining and maintaining the existence of an objective physical world is what I call “the law of unity”.
The law of unity
The law of unity is the most fundamental law of physics. In fact, it can be argued that it is the only law of physics. All other physical laws derive from it. It can be stated very simply:
The physical universe is one.
This may appear as a trivial tautology. The word “universe”, after all, comes from Latin universum, which literally means “turned into one”. But without this basic premise, without the assumption of the unity of the physical universe we observe, no science would be possible.
The law of unity is implied in all scientific theories. Even the most dubious scientific hypotheses, like the multiverse or the many-worlds interpretation of quantum mechanics, rely on the law of unity within each of the hypothetical universes they postulate. Regardless of whether parallel universes exist or not, the physical universe we observe has to be and remain one. We all observe the same universe. Without this fundamental unity, science would be impossible.
By postulating the law of unity, we aren’t therefore making any outrageous claims. But this simple law is enough to explain the consistency of all our observations (that is, of our sensations). All our sensations have to be consistent: otherwise there would be no physical world.
We can see this from two opposite but ultimately equivalent angles:
1. The sensations of all living organisms are mutually consistent because the physical universe is one.
2. The physical universe is one because the sensations of all living organisms are mutually consistent.
From the perspective of the materialist paradigm, statement 1 makes perfect sense, while statement 2 is obviously absurd. In the sensorial view, both statements are synonymous and tautological: the physical universe is nothing but the sensations experienced by all living organisms.
Physical vs psychological vs physiological qualia
It may be helpful here to make a distinction between two types of qualia. Physical qualia are what in more familiar terms we call sensations. Psychological qualia, on the other hand, are what we usually call feelings (emotions), and thoughts (mental representations).
Psychological qualia are purely subjective. They are located inside the nervous system of a living organism (mainly in the brain, but not exclusively). Physical qualia are both subjective and objective. They are subjective because, to exist, they require a subject: they imply the presence of at least one living organism capable of sensing. But they are also objective, because they have a particular, objective location in space-time. And they are shared by all living organisms capable of sensing those particular qualia. They constitute the objective reality we all share: the physical world.
Thus, according to the sensorial view, physical qualia (sensations) are not located in the brain. All physical qualia are located in the particular point in space-time where they appear to be.
A good way to ascertain the difference between psychological and physical qualia is to consider mental imagery. If I close my eyes and imagine the colour red, or visualize a blue sky, I will experience, at best, a faint replica of the actual experience of seeing red or looking at a blue sky. An extreme case are people with aphantasia, who are unable of forming mental images at all, but can perfectly see and experience physical qualia.
The same happens with dreams, where all colours, sounds, smells and tastes are much dimmer than in real life. This is especially obvious to anyone who has experienced lucid dreams. In lucid dreaming, the mind is awake enough to recognize the striking disparity between dream (mental) qualia and real-world (physical) qualia.
Psychological qualia can be extraordinarily intense and rich in special situations. For example, during a psychedelic trip it is possible to experience very vivid colours with eyes closed. Or in deep mediation states, one can experience a bright inner light. But in normal situations, the clear difference between sensations (physical qualia) and mental imagery (a subtype of psychological qualia) is a good argument against the mainstream, materialistic view that sensations are produced by the brain.
A related topic we must briefly discuss here is perception. Human perception is a complex process that involves physical qualia, psychological qualia, and a third type of qualia that we can call physiological qualia.
It is important to make a clear distinction between sensation and perception. These two terms are often used interchangeably, but they refer to profoundly different phenomena. According to the sensorial view, sensation is fundamental and happens at the level of the living cell. Perception, on the contrary, requires a complex network of specialized cells: nerve cells (neurons).
Sensory neurons translate sensations into sensory information. That information is then transmitted to the brain, where it’s organized and interpreted. This is perception. The process is triggered by physical qualia (sensations), but the end result are psychological qualia: mental images. Between the two, we have a third type of qualia, physiological qualia, happening in the nervous cells.
Perception is a fallible, often unreliable process, as many examples of optical illusions illustrate. Sensation, on the other hand, according to the sensorial hypothesis, is completely reliable: it constitutes the objective physical reality all living organisms share.
Sensation and perception normally happen at the same time, making it difficult to distinguish experientially (and not just conceptually) between the two. But in special cases, like in some optical illusions, the difference between the two becomes obvious. An example of this are the negative afterimages one can perceive after staring fixedly at a picture. Those afterimages are an instance of physiological qualia, detached from the physical qualia that triggered them. Physiological qualia are more vivid than psychological qualia (mental imagery), but dimmer than physical qualia (sensations). They aren’t shared, but private, remaining inside the nervous system of a particular living organism. But they are predictable and reproducible, because they have an objective physical base: they are echoes, reflections of the physical qualia that elicit them.
Since in this essay we are concerned mainly with the physical world, every time I use the term qualia from now on it must be understood that I’m referring specifically to physical qualia.
The two postulates
A beautiful aspect of the sensorial hypothesis is that, like special relativity, it is a principle theory which can be derived from only a few basic postulates, and whose ultimate aim is to explain the consistency of the observations (more precisely, the sense experiences) of all potential observers (meaning, in the sensorial framework, all living organisms).
In the case of sensorialism, the basic postulates can be reduced to two:
1. Sensations (physical qualia) constitute the fundamental physical reality.
2. The physical universe is one: i.e., the sensations of all living beings are necessarily consistent (the law of unity).
According to the sensorial hypothesis, everything else, including all the known laws of physics, can be evolved from those two postulates. For example, the fact that the speed of light is (has to be) the same for all observers is a direct consequence of the law of unity. The same applies to the principle of relativity. Any other arrangement would result in paradoxes and inconsistencies.
The evolution of the physical universe
To an old-fashioned scientific mind used to mechanistic explanations, the sensorial hypothesis may look like a sort of nonsensical conspiracy theory, an absurd example of magical thinking.
A conventional scientific mind may ask, for example: How can all our sensations be mutually consistent, without an underlying set of fundamental physical laws to account for those sensations? After all, the law of unity is only a basic principle that doesn’t seem enough to account for the amazing complexity of the shared universe we experience.
The answer to this question is straightforward: The physical universe we live in has evolved along with the living organisms that unwittingly co-create it day by day with their sensations. We can only assume that the universe experienced (sensed) by our first ancestors (the common ancestors of all living bacteria, archaea and eukaryotes (protists, plants, animals and fungi)) must have been much simpler than the one we observe now. The complex physical laws that modern physicists describe are the result of about four billion years of evolution of life on Earth. Those physical laws do exist, but they are not fundamental. They are steadily evolving.
But, the mechanistic mind might insist, why should our sensations be consistent, in the absence of any fundamental laws of physics to explain that consistency?
My answer to this second question may seem rather sneaky, but it’s akin to the multiverse hypothesis or the anthropic principle in cosmology: Every organism or species that didn’t faithfully follow the law of unity would inevitably be left out of our shared universe. Since (according to the sensorial view) there are no fundamental laws, there is nothing to preclude this possibility. And yet, all living organisms we observe around us do follow the law of unity because, if they didn’t, they wouldn’t be here, in this universe!
From this perspective, it seems possible that during the long evolution of life-forms on Earth some lineages of living organisms might have branched out, evolving into separate physical universes. There could be hundreds, thousands, perhaps millions of those “parallel” universes. What separates us from them is a perceptual barrier.
If there is some truth behind the UFO/UAP phenomenon (I’m personally agnostic about it), this could be the explanation. The mysterious beings some people have apparently encountered could be descendants of living organisms that separated from our own ancestors millions, probably billions of years ago (this “branching out” of physical universes seems more likely at the level of relatively simple organisms). The fact that they are inhabitants of a different physical universe, with different physical laws, could explain the weird phenomena that UFO witnesses report. It also would explain the difficulty in establishing communication with those beings, our distant relatives.
This is pure speculation, of course. The only assertion I can make about UFOs is that, in the sensorial view, it doesn’t make sense to believe that we are being visited by extraterrestrial space-travellers. In the sensorial framework, it is absurd to imagine that the planets we observe in outer space could be inhabited by living beings sharing our same physical universe (i.e., our sensations). That would only be possible if those “visitors from other planets” were related to us. In other words, if life had travelled between planets in the distant past (panspermia). But there is no scientific evidence or logical reasoning to support that hypothesis.
The sensorial interpretation
Sensorialism’s main strength is that it provides us with a straightforward, ridiculously simple answer to the apparent riddles of quantum mechanics. In the sensorial view, the quantum realm is nothing but a virtual realm of probabilities of sensations (qualia). The mathematical equations (e.g. the wave function) employed by physicists to make predictions are nothing but an indirect description (using concepts like “particles”, “fields”, “energy”, “momentum”, etc.) of the way the probabilities of sensations evolve in space-time.
This is the sensorial interpretation of QM, which I will illustrate with four well-known thought experiments:
A. The double-slit experiment
Let’s imagine a source of light placed in front of a screen, and a panel with a double slit placed between the two. If we look at the screen, we will see an interference pattern. This shows that light behaves as a wave. A wave of what? A wave of probabilities of qualia localized in space-time.
When I look at the screen I don’t see a wave. I see qualia distributed in a fixed pattern: the interference pattern. Some points on the screen appear bright, while others appear dark. The best way to describe this phenomenon is by applying the concept of “photon”. A photon is commonly defined as a quantum of light: in the sensorial view, this means the minimum amount of light that can be sensed by living organisms.
(Experimental research has shown that the photoreceptors in the human retina are capable of responding to single photons. However, neural filters only allow a signal to pass to the brain to trigger a conscious response when at least about five to nine arrive within less than 100 milliseconds. Sensorialism isn’t predicated on consciousness, but with sensing itself, be it conscious or unconscious.)
My eyes (and the eyes of many living organisms) can distinguish if a photon hits a particular spot on the screen or not. This forces the photon to behave like a particle (with a definite location in space-time) as it reaches the screen. On the other hand, my eyes cannot distinguish if a photon is going through one slit or the other. Thus, the photons behave as waves of probabilities as they go through the double slit.
Of course, there is no such thing as “photons behaving as waves”. Or as particles, for that matter. There is only qualia and probabilities of qualia. Concepts like “photons”, “wave functions”, etc., are just the conceptual, mathematical tools physicists use to describe the evolution in space-time of probabilities of qualia.
The fact that probabilities of qualia evolve in a regular, predictable, mathematically describable manner is the result of the law of unity. Without this regularity and predictability, the unity of the physical world (that is, the consistency of the sensations of all living organisms) wouldn’t be possible.
Coming back to the traditional double-slit thought experiment, let’s imagine now that we introduce a device capable of detecting, for each photon, if it goes through one slit or the other. What does this actually mean? It means, quite simply, that we are introducing a contraption capable of making visible (sensible) something that wasn’t. This is akin to using a microscope, or a telescope. By using this sort of devices, human scientists are actually expanding the physical world (which is the sensible world).
Once the “which-path detector” is in place, the photons passing through the double-slit are forced to behave as particles and go through one slit or the other. The interference pattern on the screen will disappear. This has nothing to do with “which-path information becoming available”. It has to do with the fact that the which-path detector will display its results in some form that human senses (or the senses of other living organisms) will be able to sense: like, for example, black numbers on a white computer screen.
This simple thought-experiment provides a beautiful, straightforward illustration of what constitutes the boundary between the macroscopic world that classical physics describes and the quantum world.
The crucial point here is that the behaviour of photons in the double-slit experiment is in no way influenced by the presence or absence of human (or other living) observers. It is the presence of the which-path detector what changes the photons’ behaviour from wave-like to particle-like, by introducing a strict correlation with a new set of probabilities of qualia: the detector’s display.
To further clarify this, let’s imagine that we have a detector that will flash a red light if the photon goes through the left slit, and a green light if the photon goes through the right slit. It doesn’t matter if there’s anybody present in the room, looking at the detector. Or if the only person present happens to be colour blind. The only thing that matters is that, according to the law of unity, any potential observer (in this case, any human being or living organism capable of sensing the difference between red and green light that could potentially enter the room and look at the detector) has to sense exactly the same qualia at each precise point in space-time. That constraint is what forces the photons to behave like classical particles as soon as they reach the detector.
This also illustrates what constitutes a measurement. In the double-slit experiment, the measurement happens the moment we introduce the which-path detector. More precisely, the measurement of a particular photon takes effect when that photon reaches the detector. (More precisely still: given that real-world double-slit experiments usually involve several detectors, the measurement takes effect when the photon carrying the which-path information reaches the relevant detector.)
Please note: the consciousness of any potential observers of the experiment plays no role in this.
B. Schrödinger’s cat
The same understanding applies to Schrödinger’s famous cat. We all know the scenario: we have a cat inside a closed box, with some radioactive substance, a Geiger counter and a diabolical mechanism that will kill the poor cat the instant the Geiger counter detects a radioactive particle. Since the radioactive substance is in a quantum superposition of states, does that mean that the cat will also be in a superposition of states until we open the box?
The answer is, obviously, no. The radioactive substance is in a superposition of possible states simply because those states are not detectable by the human senses (or the senses of other living organisms). But the states of cats and Geiger counters are.
It doesn’t matter when we open the box, or if we open the box or not. The moment we introduced the Geiger counter into the box, the measurement was done. (More precisely: the measurement takes place as soon as the Geiger counter’s detector is in a position where a potential particle emitted by the radioactive substance would reach it.)
Let’s say that the Geiger counter, when switched on, displays a green light. If it detects a radioactive particle, the green light changes to red (we can leave the poor cat out of this). The Geiger counter can never be in a superposition of states, because, according to the law of unity, any non colour-blind observer (human or otherwise) that can potentially look at the Geiger counter has to experience the same qualia: green or red.
We can look into the box whenever we like. If the light is green, we’ll know that no atomic decay has happened yet. If the light is red, we’ll know it has.
From this perspective, the whole thought experiment seems rather silly. “What was the fuzz all about?”, one might say. “Why did people need to come up with all those crazy ideas like ‘many worlds’, to explain this straightforward thing?”
Well, of course, the problem only seems straightforward and simple once we have given up the notion of self-existing “matter” (be it particles, or wave functions, or whatever), and realized that what constitutes physical reality is nothing but qualia and probabilities of qualia.
There are no “particles” inside the radioactive substance. There are only probabilities of qualia. Only those probabilities can be in superposition. Nothing else can.
C. The Elitzur-Vaidman bomb tester
In this light, the apparent weirdness of the Elitzur-Vaidman bomb tester¹ also disappears. This ingenious thought experiment involves a single photon interferometer with two detectors, D1 and D2. It is arranged in such a way that, due to destructive interference, no photon is detected at D2. All photons are detected at D1. Only if we block one of the paths of the interferometer will we get photons detected (with equal probability) on both detectors.
We then have a stock of bombs, of which we know that some of them are faulty. This particular type of bomb is supposed to explode if hit by a single photon, but the faulty ones don’t do anything. We now can use the interferometer as a bomb tester, by placing a bomb at a time on one of the paths.
If the bomb is a dud, we will get a click at D1. The photon is interfering with itself. If the bomb is live, it will either explode, or the photon will be detected in either D1 or D2. The photon is going through one path or the other. Thus, if we get a click at D2, we will know that the bomb is working, without detonating it.
Physicists have puzzled over this “interaction-free measurement”. Some have even claimed that this “paradox” supports the many-worlds interpretation. But none of this is paradoxical in the sensorial view.
In the framework of the sensorial interpretation the measurement described here simply isn’t interaction-free. The interaction (which is the measurement) happens the moment we place a live bomb in the path of the photon. The mere presence of the bomb (which works here as a detector, akin to the Geiger counter in the previous thought experiment) forces the photon to behave like a classical particle, destroying the superposition.
With a faulty bomb, there is no interaction and the photon remains in a superposition of possible paths: our senses (or those of any other living organism) cannot distinguish if the photon is going through one path or the other. At the end of it’s travel, there can only be a click on D1. The probabilities of qualia are unaffected.
But when we introduce a live bomb, the probabilities of qualia change: if the photon goes through one path we will hear a click at D1 or D2. If it goes through the other we will hear the deafening sound of the bomb exploding (or see a flash, or whatever). Thus, following the law of unity, each single photon has to consistently take one path or the other.
D. EPR-Bell
Another good illustration of the sensorial interpretation is the Einstein-Podolsky-Rosen² thought experiment, and it’s development by (Bohm and) Bell³. The apparent “spooky action at a distance” that bothered Einstein so much is explained and predicted by the law of unity. In the sensorial interpretation, non-locality is a given.
In other words: the correlations between distant measurements predicted by quantum mechanics, which Bell showed to violate the constraints (inequalities) imposed by any local hidden-variable theory, don’t seem problematic (or even surprising) from the sensorial perspective.
A key element here is that the states of two entangled “particles” only have to be consistent when exactly the same measurement is performed on both (measuring momentum, or position, or spin on the same exact axis, etc.). This is a clear hint at the fact that subatomic particles, or the wave functions that describe them, have no physical reality by themselves. The only physical reality is qualia: in this specific case, the particular set of qualia that results from performing a particular measurement.
The sensorial interpretation vs Relational Blockworld
Of all the interpretations of quantum mechanics I’m aware of, the most similar to the sensorial interpretation is the Relational Blockworld (RBW) interpretation proposed by Michael Silberstein, W.M. Stuckey and Timothy McDevitt.⁴ Although the sensorial interpretation has been independently developed by myself, I must acknowledge a debt to these authors in some of the wording I’m using in my most recent formulation (which is this one).
I can say, for example, that the sensorial interpretation of QM is a “psi-epistemic one that is based on principle explanation as opposed to constructive, dynamical or causal mechanical explanation”, and that “the principles in question constitute adynamical global constraints ranging over spacetime, not unlike those constraints underlying special relativity”⁵.
However, there are some important ways in which sensorialism differs from RBW. To begin with, RBW is a full-fledged scientific theory defended in a series of published papers and books by three veritable academics (philosopher Michael Silberstein, physicist W.M. Stuckey and mathematician Timothy McDevitt), while the sensorial interpretation is little more (at least for now) than a vague, sketchy idea in the mind of yours truly.
Another significant difference is that RBW is rooted in neutral monism, a metaphysical theory endorsed by philosophers like William James and Bertrand Russell, which proposes that the fundamental nature of reality is neither physical nor mental: it is “neutral”.
According to neutral monism, the mental and the physical are nondual. In the words of Silberstein and Stuckey: “Physics is inherently all about the possibility of and rules of experience, but not because the world is mind dependent. Just as there is no metaphysical dualism of the “inner” world of experience and the “outer” physical world, there is no inherent dualism of psychology and physics.”⁶
This metaphysical position is, I think, a great step forward in comparison to mainstream physicalism. But there are several problems with this view. First, even if it looks good on paper, it is very difficult to imagine what this “neutral” fundamental nature of reality might be like. The notion is, to put it simply, too abstract.
A more serious problem, though, is that in this neutral monist view all our conscious experiences, including thoughts, emotions, decisions, etc., are inextricably included in the realm of physics. Since there is no dualism between mental and physical states, no separation can be made.
For example, when discussing a delayed choice quantum eraser experiment in which an apparent retrocausality can be observed, Silberstein and Stuckey say that “adynamical global constraints in spacetime also constrain the choices of conscious agents. Thus, physics is already part of psychology in that it places real constraints on what can be experienced to include memories (classical records) and choices.”⁷
The sensorial view, by contrast, is based on a less simplistic metaphysics. Sensorialism is not a theory about the whole of reality: it is a theory about the physical world. In the underlying metaphysics⁸ there is a fundamental nondual unity to all of reality, but there are different realms that can (and must) be discriminated.
The crucial distinction we must make here is between the realm of sensation (the physical realm) and the realm of consciousness (the mental realm). The lack of clear discrimination between the two is one of the main obstacles that has historically impeded the progress of Western science and philosophy. Without going into much detail, I’ll try to summarize this problem in the following section.
Awareness vs consciousness
“Awareness” and “consciousness” are terms that are often used interchangeably. Even when a distinction is made in some cases, it is widely believed that these two concepts overlap to some extent. There have been attempts, for example, to define consciousness as “self-awareness”. In my view, this state of affairs reveals a deep misunderstanding of the fundamental nature of both awareness and consciousness.
Following A. H. Almaas, I propose that awareness and consciousness are fundamental dimensions of reality, and that they constitute two distinct realms. In this view, awareness is the realm of qualia, while consciousness is the realm of cognition (knowing). We must distinguish between a quale in itself (the actual sense experience of the colour red, for example) and the recognition (knowing) of that quale as what it is (recognizing the experience of red as “red”).
This subtle but crucial distinction is not easy to do, because in our everyday experience awareness and consciousness usually go together, apparently inextricably linked. It seems almost impossible to separate a particular quale (an instance of red) from our conscious knowing of it (“this is red”). Yet this separation can be experientially achieved through years of meditation and concentration practice.
A more expeditious method is the use of psychedelics: in deep psychedelic states one can experience qualia without the least recognition of what those qualia are. In these peculiar states the habitual visual experience of the world seems to melt, to dissolve into a moving ocean of the most vivid colours, while the cognitive capacity to identify or recognize those colours (or the whole experience in itself) completely disappears. The suspension of all cognitive capacity in these psychedelic experiences is what makes them so difficult to remember afterwards.
If we look at other living organisms, we can hypothesize that plants don’t have consciousness (cognition), since they lack a central nervous system. But they clearly possess awareness. They can sense the sunlight, for example, which enables them to grow towards it. The crucial point here is that, in the sensorial view, the physical world that all living organisms share exists on the level (realm, dimension) of awareness. Not on the level of consciousness.
The failure to make this distinction between awareness and consciousness is what makes it so difficult for physicalist scientists to distinguish between the actual physical world (our sense experience of it) and our ideas about it. Things like photons, electrons, quarks, quantum fields, etc., are just ideas. Only sensations (qualia) are physically real.
It’s also what leads physicists to believe that the science of physics might have something to say about free will, or about the nature of consciousness. It doesn’t.
The same failure, on the other hand, is what makes philosophers of mind and cognitive scientists get bogged down in endless disquisitions about qualia while discussing consciousness, not realizing that qualia don’t pertain to consciousness, but to awareness.
An experimental test for the sensorial view
The sensorial view I have tried to defend here is a purely philosophical description of physical reality, based on a wider metaphysical framework that includes non-physical realms (consciousness, etc.). It provides, I think, a simple and elegant interpretation for quantum phenomena. The question is, can it become a proper scientific theory, to justify the term “sensorial hypothesis” I’ve used on the previous sections? Can it be tested experimentally?
As it turns out, I think it can. Obviously, I don’t have the technical know-how to give a definite answer, but I believe it should be possible to put this interpretation to the test by applying a modified version of a well-known real-world “delayed-choice quantum eraser” experiment performed and reported in 1999 by Yoon-Ho Kim, R. Yu, S. P. Kulik, Y. H. Shih and Marlan O. Scully.⁹
An Argon laser pump aims photons at a double slit. After a photon passes the slits it impinges on a Barium borate (BBO) crystal placed behind the double slit. The optical crystal creates an entangled pair of photons via spontaneous parametric down conversion at the spot where it hit.¹⁰
The “signal” photon continues towards detector D0. The “idler” photon is deflected by a prism and encounters a series of beam-splitters (BS) and mirrors (M), so that: if a photon is detected at D3, it must have travelled through the lower slit; if a photon is detected at D4, it must have travelled through the lower slit; if a photon is detected at D1 or D2, it can have travelled through either slit (i.e., it is in a superposition of possible paths).
A plot of signal photon counts detected by D0 can be examined to discover whether the cumulative distribution of “hits” forms an interference pattern. Using a coincidence counter, it is possible to isolate the entangled signal from photo-noise, recording only events where both signal and idler photons are detected. In accordance with the predictions of quantum mechanics, Kim et al. found interference patterns when they looked at the signal photons whose entangled idlers were detected at D1 or D2, but discovered simple diffraction patterns with no interference when they looked at the signal photons whose entangled idlers were detected at D3 or D4.
The experiment I propose to test the sensorial interpretation is basically the same¹¹, but with two modifications: First, the experimenters must make sure that detectors D1, D2, D3 and D4 give no perceivable clue whenever they detect a photon. No audible “clicks” or visible changes in the detectors are permitted. Detector D0, on the contrary, will show perfectly visible results (like, for example, dots on a screen marking the impacts of signal photons).
Second, the results of the experiment will be examined not by human experimenters, but by a computer (AI). This computer has to be able to record all the photons detected at the five detectors, select the entangled photon pairings using the coincidence counter, and ascertain if the distributions of the signal photons on D0 show interference patterns or not.
All these calculations have to take place “in the dark”. The computer will display no detailed information about the behaviour of the idler photons. Moreover, that information will be carefully erased after the calculations are finished, so that it will be irretrievable by the human experimenters. The only information the computer will display is the following:
- If when examining the distribution of the D3 photons (i.e. the signal photons whose entangled idlers were detected at D3) no interference pattern is found, the word NO will appear on the computer screen.
- If when examining the distribution of the D3 photons (i.e. the signal photons whose entangled idlers were detected at D3) an interference pattern is found, the word YES will appear on the computer screen.
The sensorial interpretation predicts that the result will be a YES. All other interpretations (as far as I know), following the standard predictions of quantum mechanics, predict that the result will be a NO.
The reason for this divergence is that, according to the sensorial hypothesis, since there is no change in the probabilities of qualia correlated with the photons hitting detectors D1, D2, D3 or D4, the idler photons will remain in a superposition of possible paths. The which-path information will be (in principle) available to the computer, but it won’t be translated into any changes in qualia.
This raises an intriguing problem: if the idler photons remain in superposition, how can they be detected at any of the four detectors D1, D2, D3 or D4? According to the predictions of the sensorial hypothesis, they won’t. All idler photons will seem to vanish without a trace. Therefore, it will be necessary to add another instruction to our computer program:
- If no photons are detected at D3, the expression YES!!! will appear on the computer screen.
(Depending on the set-up of the experiment, the sensorial interpretation predicts that we might see an actual, visible interference pattern at detector D0!)
To make sure that the measuring apparatus is working properly, we can set up the computer to run sequentially on two different programs or modes. On mode 1, the computer will display in detail the results on all five detectors. In this mode, we should expect the predictions of standard quantum mechanics to be met (interference patterns when examining D1 and D2 photons, no interference patterns in the case of D3 and D4 photons). On mode 2, the previously described instructions will be followed.
And that’s it. If this experiment is technically feasible (I can’t see why it wouldn’t be, but then again, I’m no physicist and no computer programmer), it could be a relatively simple way to falsify or confirm the sensorial hypothesis.
1 Elitzur, Avshalom C.; Lev Vaidman, “Quantum mechanical interaction-free measurements”, Foundations of Physics 23, 1993.
2 Einstein, A.; B. Podolsky; N. Rosen, “Can Quantum-Mechanical Description of Physical Reality be Considered Complete?”, Physical Review 47, 1935.
3 Bell, J. S., “On the Einstein Podolsky Rosen Paradox”, Physics Physique Физика 1, 1964.
4 Silberstein, Michael; W.M Stuckey; Timothy McDevitt, Beyond the Dynamical Universe: Unifying Block Universe Physics and Time as Experienced, Oxford University Press, 2018.
5 Silberstein, Michael; W.M Stuckey, “The Completeness of Quantum Mechanics and the Determinateness and Consistency of Intersubjective Experience: Wigner’s Friend and Delayed Choice”, Quantum Physics, Cornell University, 2020.
6 Ibid., p. 3.
7 Ibid., pp. 25-26.
8 See A. H. Almaas, The Inner Journey Home, Shambala, 2004.
9 Kim, Yoon-Ho; R. Yu; S. P. Kulik; Y. H. Shih; Marlan Scully, “A Delayed Choice Quantum Eraser”, Physical Review Letters, 84, 2000.
10 Fankhauser, Johannes, “Taming the Delayed Choice Quantum Eraser”, Quanta 8, 2019.
11 A much simpler experiment could be devised by removing the beam-splitters, the mirrors, and detectors D1 and D2, but for illustrational purposes I prefer to stick to the more elaborate Kim et. al. configuration.
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