What Does Quantum Mechanics Suggest About Our Perceptions of Reality?

Quantum Mechanics Suggest about Our Perceptions of Reality?Shutterstock

Quantum mechanics suggests that we perceive at most a tiny sliver of reality. Of course we already knew that! We knew that the visible spectrum is only a small part of the spectrum of electromagnetic radiation. We knew that the universe is much, much larger than our ancestors believed.  And we already knew that we are made of things that are too small for our eyes to see. So how is it news that we only perceive a tiny sliver of reality?

It’s news because quantum mechanics says that the part of reality that we do not perceive is radically different than the part of the world that we do perceive. The difference is so profound that we still don’t fully understand how to talk about quantum reality. There doesn’t seem to be any direct analogy between quantum reality and the reality we perceive with our senses.

Before I explain the gap between our perceptions and reality, I want to state that I completely disagree with the idea that quantum mechanics forces us to accept an idealist view of reality. Idealism says that the physical universe is made out of our perceptions – in other words, out of spiritual reality.  Several early interpreters of quantum mechanics thought that it supported this idealistic understanding of reality. Why would they have thought this? The reason, quite simply, is that they didn’t know how to cope with the issue of quantum indeterminacy.

Quantum indeterminacy is the unavoidable fact that not all quantities can simultaneously have determinate values.  For example, if an electron has a location, then it simply has no speed – it is neither at rest, nor is it moving slowly, nor is it moving quickly.  There simply is no fact of the matter about its state of motion.  Similarly, if an electron is in a definite state of motion, then it’s not in any particular place – not here, nor there, nor anywhere.

Let’s be completely clear about what we’re saying here.  We are not just saying that if you know the position of the electron, then you don’t know whether or not it’s moving.  We’re saying that if the electron has some position, then it does not have any state of motion.  What could this possibly mean?  Nobody is quite sure.

But the story gets more interesting.  Whenever a conscious observer tries to determine the position of the electron, she will always finds that it does indeed have a position.  Similarly, whenever a conscious observer tries to determine the state of motion of an electron, she will always find that it does indeed have some particular state of motion.  If these facts weren’t true, then we wouldn’t be able to test the predictions of quantum mechanics! So how are we to reconcile the fact that sometimes the electron doesn’t have a position with the fact that, whenever we look, it does have a position?

Some quantum pioneers, such as Heisenberg and Wigner, thought that the act of “looking” caused the electron to take on a definite state of motion, or a definite position.  And then it wasn’t much of a further leap for them to suggest that, before anybody looks, there wasn’t any electron.  If that were the case, then physical reality is brought into existence by our acts of perception.

But the path from quantum indeterminacy to subjective idealism involves several illogical leaps. First of all, why think that before a measurement occurs, no quantities possess values?  While some quantities must lack values, it was proven by Jeff Bub and Rob Clifton that many quantities can possess values even when nobody is looking.

Perhaps the reason Heisenberg and others fell into idealism is that they just couldn’t see any reason why some quantities would have values while others wouldn’t.  Why would an electron have a state of motion, but not have a position?  Perhaps they felt like Buridan’s ass, who starved because he couldn’t see any reason to prefer one pile of straw to another identical pile.

I grant that there’s a puzzle here that needs to be solved — how can we figure out which quantities have determinate values?  Several people have tried to solve this puzzle. For example, according to an idea of Louis de Broglie, which was later developed by David Bohm, reality is made out of small corpuscles that always have completely determinate positions.  But why treat particle configurations as special? One reason for thinking that particle configurations are always determinate is our eyes seem to tell us that this is the case!  Another good reason for thinking that particle configurations are determinate is that it’s possible to describe how they move in terms of elegant dynamical laws.  Thus, the possibility of Bohmian mechanics shows that subjective idealism is by no means forced on us by quantum mechanics.

Be that as it may, Bohmian mechanics does not suggest that our perceptions mirror the nature of fundamental reality.  For Bohmian mechanics also postulates the existence of a hidden field that guides the particle configurations – and this field is so mysterious that Einstein rejected it as an explanation of quantum reality.  So Bohmian mechanics might be a realist interpretation of quantum mechanics, but it doesn’t license a return to naive realism. If Bohmian mechanics is true, then the physical world radically different from our perceptions of it.

There are other interpretations of quantum mechanics that describe a deep reality that is hidden from our perception.  Two of the most plausible, but also most wild, suggestions are the configuration space interpretation of quantum mechanics, and the Everett interpretation of quantum mechanics.

According to the configuration space intepretation of quantum mechanics, the world of our perception is just a projection of an incredibly high dimensional configuration space. Again, this interpretation of quantum mechanics is realist in that the space of all configurations has its existence and properties quite independent from our observations. But once again, this configuration space is perceptually inaccessible to us — we can only see the effects it has within our much smaller three-dimensional space. The upshot, as before, is that if you really believe quantum mechanics, then you believe that the physical world outruns our perceptions of it.

Another popular way to think of quantum mechanics is in terms of the Everett, or “many worlds,” intepretation of the theory. In this case, the configuration space doesn’t cause any ontological headaches; however, the wave function of the universe must be taken to be a real thing. But now we have some real work to do in explaining why human experience portrays the world in a very different light, i.e. as something that looks to have determinate properties, when in fact it doesn’t.

But what could we possibly mean by this? How could something without determinate properties explain the appearance of determinate properties? Well, good Everettians would say that the wave function does have properties — just not those properties that appear in our observation reports (e.g. “the particle is in position ”). But what properties does the wave function have? According to a famous proponent of the Everett interpretation,

Every mathematical property of the wave function describes, or corresponds to, some property of the real, physical world.[1]

This is an intriguing idea. But what exactly are the mathematical properties of the wave function?  As a mathematical object, a wave function is a function; and a function is a certain sort of set of ordered pairs.  What kinds of properties can a set of ordered pairs have?  Well, it might contain the pair consisting of the emptyset and the number 17.  But what physical property corresponds to that mathematical property?  What if it didn’t contain that pair, but instead contained the pair consisting of a singleton set and the number 17.  What would the corresponding difference be in the physical world?  As you can see, these are fruitless questions.  It’s a bad idea to say that the wave function represents a thing whose properties are in one-to-one correspondence with that function’s mathematical properties.

Realists about quantum mechanics – such as Bohm and Everett – say the wave function is “real”; and I think that’s a good thing to say. But let’s be careful.  To call the wave function a “thing” is to commit a basic grammatical error: a state is not a thing, but a way of being.  A wave function is more like a “situation” or a “possible world,” not a thing you can touch or pick up.  Sure, we could say that situations and possible worlds “exist,” but they’re of a different kind than “things.”  Situations aren’t the fundamental bearers of properties — instead, a situation is composed of things bearing properties. Thus, we can grant that the wave function is real while denying that it is a thing; and if this is right, then it’s a mistake to think that the wave function has properties.

Another important point to keep in mind is that perception cannot possibly reveal the wave function. The impossibility here follows from the “no cloning theorem” of quantum mechanics. According to the no cloning theorem, no physical object whatsoever can reliably track (by changing its state) the quantum state of another object. In other words, the laws of nature do not allow for the existence of a machine that copies quantum states; consequently, the human brain cannot possibly track the wave function of a physical object.  So, if reality is the wave function, then we simply cannot perceive reality as it is in itself.

Where does that leave us? The remarkable thing is that we can still reliably track aspects of reality. Whatever quantity you want to measure — be it position, momentum, or spin — if you measure it twice, within a short span of time, you will find that it has the same value.  Thus, we have good reason to think that our measurements provide reliable information about reality.  This sort of reliability is good enough to guide our actions, and it provides strong evidence of the hidden reality behind our perceptions.

Discussion questions

  1. How does quantum mechanics bear on the age-old philosophical debate between materialism and idealism?  Does it tip the scale in either direction?
  2. Which view of quantum reality is most plausible?  The Bohmian view?  The Everett view?
  3. Is the quantum wave function real?  What does it mean to say that it’s real?
  4. The author argued that the quantum wave function is not a thing.  But then what does exist according to quantum mechanics?
  5. Does the no-cloning theorem support a form of perspectivalism, i.e. that our knowledge of the world is always bound to a particular perspective, and cannot encompass all aspects of reality?

Discussion Summary


In the original piece, I claimed that there is a gap between reality in itself (at least reality at the fundamental physical level) and the reality that we perceive.  I also claimed that the most elusive component of the microworld is the quantum wavefunction, which is “real,” but is not (I claimed) a “thing”. Finally, I pointed out that, due to the no-cloning theorem, human beings cannot know the quantum wavefunction of an object.

It seems that the commentators agreed mostly with the major claim that there is a large gap between reality as perceived by us, and reality in itself.  There was also substantial agreement on the fact that there our perceptions do not create reality. Our discussion then revolved mostly around the question: how are we to understand the quantum wavefunction?  In order to understand it, would we need to describe it in traditional metaphysical categories, such as substance and property?  Or can we do no better than to represent it by means of the formalism of quantum mechanics?

Unsurprisingly, we were unable to provide definitive answers to these questions. Indeed, they are some of the most difficult questions in the interpretation of quantum mechanics.  We did, nonetheless, make some progress on the question of whether or not the wavefunction is a “thing.”  In the original piece, I said that it is a “grammatical confusion” to consider the wavefunction to be a thing.  Eddy Chen, in his comment, challenged me on this point — and suggested that there are more liberal accounts of ontology where properties (for example) also count as things.

I concede this point to Chen — we could, for example, say that properties (e.g. “whiteness” or “yellowness”) are also things. But should we then allow that properties themselves have properties?  For example, should we say that the property of whiteness has the property of being a color, or perhaps the property of being a property? (But beware of falling into logical paradox here!  Does the property of whiteness have the property of whiteness?) The reason this question is important is because we want to understand whether the wavefunction itself is a physical object with properties, or whether it’s just a property of other things.

Chen argued that the really interesting question here is where to locate the wavefunction in our ontological framework. Is it merely a summary of particle configurations? Is it like a law of nature? Or is it a physical field? And if it’s a physical field, on which space is it defined — on -dimensional physical space, or on some higher dimensional configuration space?

Although much of the discussion focused on the nature of the wavefunction, there was also a lively discussion, initiated by Roger Sawtelle, about whether the laws of quantum mechanics apply to the entire physical world, or just the microworld. These days, the default assumption among physicists and philosophers of physics is that the macroscopic world does obey the laws of quantum mechanics; but somehow the measurement process and/or decoherence gives rise to the appearance that the macro-world obeys the laws of classical physics. Of course, this assumption has yet to receive strong confirmation from within physics itself. Perhaps in the coming years, experiments — such as tests of the violation of the Leggett-Garg inequality — will provide more information about the relationship between the physics of the macro- and microworlds. 

Further Big Questions:

  1. What is the relationship between the micro- and macro-world? Are the laws of the micro-world adequate to describe all occurrences in the macro-world?
  2. How can experiments be used to probe quantum reality? Can quantum-mechanical experiments provide information about the correct interpretation of quantum mechanics, and about the relationship between quantum mechanics and the macroworld?
  3. Does the quantum wavefunction exist? Does anything else besides the quantum wavefunction exist?

43 Responses

  1. markovich says:

    Mathematical properties of the wave function are determined by virtual particles of space-time on the subquantum level. These phantom string-particles create quarks from nothingness of primordial blueprints, appearing and disappearing with frequency more than 1030. The gradients of their flows generate a gravitational fields and cause the effect of expansion or contraction of the universe. They are bridging the physical 3D world through the time-space membranes with the fifth dimension of matrix of the Universe’s consciousness.

  2. Roger A. Sawtelle says:

    Quantum Physics demonstrates the myth of reductionism.  Science beieved that if it could just understand how matter worked at the most basic level it could understand how nature worked including humanity.  Quantum mechanics demonstrated that this expectation is false, because the physics of the quantum world is very different from the physics of the human world. 

    Some take that to mean that since we cannot explain completely the mechanics of the quantum world a materialistic understand of the world is impossible.  While that true, that does not mean that only a “idealistic” understanding of the world is possible.  This is a false dichotomy which dominates our Western dualistic culture. 

        The our world contains matter/energy which follows rational laws.  To understand it we need to understand both, but we also need to go beyond matter/energhy and rationality to understand the purpose and meaning of life. 

       This raises the question as to whether life has meaning.  A quick arguement:  Humans evolved by natural selection to the top of the food chain.  Humans have two definite “evolutionary advantages” over other species, rationality and purpose which enables them to explore nature and cooperate with others.  Rationality and purpose would not be evolutionary advanages given to us by our DNA if they were not somehow embedded in nature.  Now it is true that humans are now using that rationality and purpose in as negative way against nature and against each other so our naqture is not necessarily a positive influence.

    Humans are physical, rational, and spiritual beings.  We have bodies, minds, and spirits. 

     Animals have bodies, and they also have nervous systems and brains which enables them to process information at various levels.  We can also observe that animals have feelings and personalities, which are the beginnings of a spiritual life.     

    Non-living things are physical to be sure, but they also have a rational structure which allowe them to be a part of a rational universe.  This rational universe has a purpose which give meaning and unity to all.  Thus matter/energy also has its physical, rational, and spiritual aspects, which are different from the bio world.

          God by definition is spiritual.  Christians believe that God is the Source or Meaning of life and the End or Purpose of life.  Whether one believes in God or not, life does have a real meaning and a real purpose, as opposed to a pretend or subjective meaning and purpose.

    Life has three aspects, the physical, rational, and spiritual, just as Reality has three aspects, times, space, and history; and time has three aspects past, present, and future: and electricity has three charges, positive, negative, and neutral; and the atom has three aspects, neucleus, the electron shell, and the strong force which unites them.; etc.

    A very important important discovery has indicated how systems of different kinds, the rational with the physical and the spiritual can interface.  This is Emma Noether’s Theorem of Symmetry.  This Thoerem indicates that nothing is lost through change.  It also indicates that two different systems can interface with each other in a symmetrial way.  Thus the mind/brain which is primarily rational can know the physical world which is primarily physical. 

      This along with the proof of Einstein that the world is relational opens the way for us to develope a new philosophical world view to replace wornout Western dualism.

    • Hans Halvorson says:

      In response to Mr. Sawtelle’s comment, I’m not completely convinced that quantum mechanics rules out reductionism.  In particular, isn’t it possible that the microworld is radically different from the macroworld, and yet the macroworld is completely dependent for its being on the microworld?  Isn’t every fact about the macroworld determined by what is going on in the microworld?  Consider an analogy: I can create a painting.  This painting depends on me for its existence.  And yet the painting is radically different from me (for example, it doesn’t have a brain). 

      The lesson I take away from quantum mechanics is the the microworld is deeper than human perception can ever reach, even with the aid of instruments.  But I think it’s completely possible that what we do know about the microworld is enough to tell us everything about the physics of the macroworld.  In other words, we don’t need another physics for the macroworld that is different from the physics of the microworld.

      I happen also to believe that there’s much more to life than what physics can ever tell us.  For example, physics won’t tell me that that my wife is a person rather than just a chunk of physical matter.  But that belief of mine (that physics is limited) is independent of what I know about quantum mechanics.  I would have believed that even if I didn’t know anything about quantum mechanics.

      • Roger A. Sawtelle says:

         Isn’t every fact about the macroworld determined by what is going on in the microworld? 


        I think the answer to your question is No.  When you paint a picture of your wife, that is not determined by what is going on in the microworld, unless you think that you are controlled by your microworld, which I would submit is not true.

        Generally speaking materialism leads to determinism, while idealism leads to freedom, which is the basis of this discussion.  I think that you affirm that we do live in a world determined by the laws of nature, but at the same time humans do have a remarkable amount of free will. 

        How can we explain this paradox?  My three fold nature of reality is a start. 

         P.S. We already have a quantum physics which is different from the physics of the macroworld. 

        • Hans Halvorson says:


          What quantum mechanics showed us, I think, is that the physics of the macroworld is only approximately true.  Strictly speaking, Newtonian physics is false.  Macroscopic physical objects do not really obey Newton’s laws; they really obey the Schroedinger equation.  (To be even more accurate: macroscopic physical objects aren’t even really physical objects in the way that Newtonian mechanics supposed they were.  Instead, macroscopic physical objects are configurations of quantum fields.) 

          So if quantum mechanics is universally true, then how do humans have free will?  I don’t have a solution to that problem.  But I don’t think the solution lies in the direction of saying that human bodies don’t obey the laws of quantum mechanics.  One possibility here is that we could adopt compatibilism, i.e. the belief that free will is possible in a deterministic universe.  Another possibility is to think that human freedom is enabled by the indeterminacy of the quantum world.  But this second possibility is too speculative; I wouldn’t bet my freedom on it.

          • Roger A. Sawtelle says:


            Thank you for your response. 

            A serious contradiction seems to have arisen.  You said in your first response that you know that physics does not have all the answers.  However you have failed identify where we need to go to discover the answers to the problems that physics does not answer.  Also it seems to me that you are acting as if physics does have all the answers.  The question does seem to be Is the physics of the universe determinate or not and do human bodies obey the laws of physics?

             First, let me ask, why do you ask if human bodies obey the laws of physics, rather than does the human mind obey the laws of physics?  Bodies are physical, while the mind and brain are mental. 

            Bodies obey physical laws, while the neural system is not physical and obeys the laws of perception and thinking.  I know that people like Dennett and Dawkins say that the brain is physical and people cannot think, but they are mistaken.  

             Second, you seem to make no distinction between the way the macroworld works and the quentum world works, which do against all that I have read.  In the quantum world we have the duality of waves and particles, whereby matter acts like energy and energy acts like matter, while in the macroworld this does not happen. 

            In the quantum world we have entanglement and the inability to measure location and velocity at the same time.  Not in the macroworld.  In the quantum world we have probabilistic views, but I am not aware the H2 and O1 join to create water less than 100% of the time in the macroworld.

               The evidence shows that the quantum world and the macroworld are governed by different rules, however they are able to interface as Noether’s Theorem indicates in a symmetrical manner. 

             I checked out Schroedinger equation which you said is the basis of all physics.  The source I consulted did not confirm that it was directly applicable to the macroworld.  It did indicate that it was based on a conservation theory, which would tie it to Noether’s Theorem which is also a conservation theory.  In my understanding that the Schroedinger’s cat question is a good example of trying to tie the quantum world to the macroworld, which does not work.  . 

            I do not believe that either quantum physics or macroworld physics is universally true, but that is not the reasaon people have free will.  People have free will because they can think and make decisions. Also people have free will because the world is not just black and white, but black and white with a lot of gray in between. 

               People have free will even though they live in a universe governed by laws is because these laws are rational which allows people to make choices.  The universe is both physical and rational.  People have free will because the universe has meaning and a purpose.  Our decisions mean something so we can be morally responsible beings.  People have free will because we need to make decisions which are compatible with our responsibilites to ourselves, to others, and to the well being of the universe or God.  

              As I said before we do not live in a purely physical universe, nor a purely rational universe, or a purely spiritual universe.  We live in a universe which is all three.  They are all three compatible, because all three exist in harmony in the universe, when we live in harmony with each other.  


  3. Vladimir says:

    1. The fundamental physics endures deep philosophical “crisis of understanding”, “crisis of interpretation and representation”, crisis of existential uncertainty. To understand is means “to seize the structure”. For “setting” primordial structure of the Universum as a whole should be considered ontology and dialectic “eidos” and “logos”, the dialectic of absolute forms of existence of matter (absolute limit states) in triunity: absolute rest + absolute motion + absolute becoming.

    2. Quantum mechanics – the parametrical theory without ontologic justification (basification). It well works as Ptolemaeus’s theory worked. But its ontologic basis remains not intelligent deeply.

    3. “Quantum wave function” – only mathematical language. Ontologic structure of reality as structure of language (“house of being”): linearly-wave-vortex.

    4. The ontological basis of fundamental physics: triunity of absolute forms of existence of matter.

    5. Sir John Marks Templeton gives us the help and the direction of research: “Do Scriptures need interpreting to accommodate an expanded notion the universe?”… “The unknown is not unknowable and is vastly greater than the know” and “There are more possibilities in the universe than one can imagine”.
    In the original, the Scriptures into Greek language is
    the fundamental conclusion: “In the Beginning Was the Logos… “, on Ancient Greek ν ρτ ν λόγος

  4. abed.peerally says:

    Hans Halvorson has written a good article coming from a most elusive and complicated aspect of physics and cosmology, the most difficult one there is in science if it includes the scientific explanation of the origin of the universe. The debate about materialism, idealism and perspectivalism is not ready for a meaningful one since we really do not have an explanation of  what is quantum reality in the deepest sense. It could be totally different from all that has been said so far. This is why there are so many views, very often from some of the most eminent scientists we have. For example it is not even worthwhile to distinguish between the Bohmian and the Everett’s ones for both are totally speculative. I agree with the author that the wave function is real, not a thing but a way of being. We will one day understand better what it really represents.

    The quantum reality debate really started with Einstein perhaps due to his scientific disagreement with Bohr about the nature of quantum matters. However in view of the fact I have been able to combine both GR and SR in an important aspect of cosmology into the same equation showing a 2 to 1 proportionality between them in Keplerian orbits (SAJS, 104:221-224) many pretentious description of gravity and the challenge of its mergence with GM are overrated. This SAJS is a huge discovery for it has brought GR to the same level as SR in an important manner, and to me it conclusively proves that GR is not a very great mystery and does not deserve, as Hawking did in his Grand Design, to be categorized as a sure alternative to God. Gravity is not so important to deserve this status and Hawking is creating a great inaccuracy. Likewise Hawking was very inaccurate to predict in his Brief History of Time that a Theory of Everything would soon materialize when so many of us know that not even an inkling of it exists. This is too evident when you look at the different interpretations of QM such as is so elegantly described by N. Herbert.

    I could express the following opinions to cut a long discussion short:

    ·         We have not at all settled the issue of indeterminacy/determinacy

    ·         Bohr’s view that there is no quantum reality before a measurement is done is simply wrong.

    ·         Einstein is absolutely right to claim that QM incomplete and that the so called spooky action at a distance is due to hidden variables not yet identified in QM.

    ·         Einstein is right when he says that there is no possibility of motion faster than light.

    ·         Therefore as I have said elsewhere, in a comment on Perimeter’s Arkani Hamed’s lecture some weeks back, the hidden variables of Einstein are not to me necessarily related to superluminal motion, so that the mystery of faster than light motion remains a great quiz.

    ·         I also disagree with Bohr’s belief that there is no quantum world but instead an abstract quantum description where there is no physical reality.

    ·         I also disagree with Bohm’s universe as an undivided reality in the form of a universal  wholeness which seems to suggest that everything in the universe is absolutely connected.

    ·         Similarly  I find the other extreme notion of a synthetic expression of reality arising from the so-called myriads of universes or parallel universe, e.g  Martin Rees’  universes inches away from your face and others such as a universe in your backyard and also Hawking’s gravity which will go on creating infinite universes, so there is no need for a creative mind behind the universe.

    ·         Einstein was right when he said the he wished he could understand God’s mind when the universe was created and that God does not play dice and that he is not bothered with our mathematical difficulties, as he integrates empirically.  

    ·         I believe that Einstein was right to say that there has to exist a model of reality which is behind the physical entities at every level of existence, not merely the probability of their existence.

    ·         At the other extreme of beliefs we have Von Newmann’s consciousness created reality which is rather like what Heisenberg and Bohr believed in such as observer created reality. Nothing real exists except during the act of measurement. In this philosophy there is no deeper reality but just possibilities and tendencies.

    ·         Finally I also admire the manner Bell has responded to Einstein, Podolsky and Rosen’s spooky action at a distance, but while I agree with his theorem that it is nonlocality which imposes the notion of hidden variables and of superluminal speed he has not convincingly as least to me established that superluminal motion is possible. This is a more complicated issue than can be seen now but we will learn more about Einstein’s views on faster than light speed in due course. What I can say is that it appears to exist but in reality does not.

    The debates on quantum reality, philosophy and religion in an integrated manner has great potential for the future, as long as we remember that only science can explain physical realities whilst religion and philosophy play the role of interpreters of what science has to say.

    Finally it will be shown that predictions in the Bible and Quran, we will  see, absolutely reflect the ultimate elucidation of what the universe stands for.

  5. George Gantz says:

    I might point out that the current FQXi Essay Contest (Trick or Treat – 72 essays submitted so far) offers a broad array of ideas on the connections between math and physics and our perceptions and beliefs about what is real and what is true.  It is a very sticky subject.  My own submittal points out that math and physics, in the past century particularly, have delineated hard limits to what we are ever able to know – leading to the conclusion that we have to make choices about what to believe (without knowing). I believe the world is unitary, “objective” in the sense of being common to us all, consistent and purposeful.  To me this meets the test of Occam’s razor, but more importantly, it allows me to live a meaningful life. 

    • Hans Halvorson says:

      Dear George,

      I completely agree with you that math and physics in the previous century have pointed toward the fact that, “we have to make choices about what to believe (without knowing).”  That’s even true about the different interpretations of QM.  Some people choose to believe in the Everett picture, for it tells a story that gives some meaning to their lives.  Other people choose to believe in the Bohmian picture, for they prefer the story that it tells. 

      Your FQXi essay sounds interesting.  What’s the title, and can I find it online?

  6. Eddy Chen says:

    I enjoyed reading Professor Halvorson’s short article on quantum mechanics and our perceptions of reality. It highlights some very interesting puzzles about quantum mechanics that have been with us since the very start of quantum mechanics. At first glance, quantum mechanics, at least according to many people, imply certain kind of radical indeterminacy (maybe crying out for revision in our logic), measurement uncertainty, the rejection of scientific realism (or maybe even a broadly realist view about the objective nature of the world), and so on. The essential ingredient in those puzzles, as hinted in the article, is the wave function that (totally or partially) represents the state of a quantum system. We ask: what is the nature of such a thing, called the wave function? To be sure, we do not need to fully settle this question before addressing the puzzles about indeterminacy, uncertainty, and anti-realism. There are many adequate and realist interpretations of quantum mechanics that prove that neither radical indeterminacy (or quantum logic or quantum probability) nor anti-realism is forced upon us by quantum mechanics. But let us now, for the purpose of this discussion, talk generally about the wave function and its role in quantum mechanics. 
     In the non-relativistic quantum theory, the wave function is represented by a complex valued (or spinor valued) function defined on the configuration space (all the ways that a physical system can be arranged). Over time the wave function changes its values according to the Schrodinger equation—the central dynamical equation in the quantum theory. (Spontaneous collapse theories such as GRW and CSL modify such an equation and add an additional probabilistic jump rule for the wave function.) From the wave function, we can extract predictions (based on the Born rule) about the probabilities of the  behaviors of, say, electrons passing through a pointed magnet (the Stern Gerlach device) and many other things (e.g. using more fancy version of quantum theories for particle behaviors in the experiments done at LHC). The wave function is at the center stage in the quantum theory and is at the heart of its empirical adequacy. Now, what is the nature of the wave function? Well, we think of it as representing the physical state of a system. But a system of what? 
    Well, to answer that question, we need to look at specific proposals for making the quantum theories precise. Quantum mechanics, as used in many physics textbooks and by many physicists, is more or less a recipe. If I use a recipe to make a delicious meal, I may not know why the specific steps are useful and why certain combinations are effective as they are. Similarly, if I learn the quantum recipe, I may be able to extract predictions according to the prescriptions (give the system a wave function in certain ways, then assign a Hermitian operator to what I want to observe, and use the Born rule on the wave function. Lo and behold! I have calculated the right probabilities of electrons going up and electrons going down!) That offers us no real understanding about the physical nature of the world, just as most food recipes don’t offer much insight into the bio-chemical process involved in cooking a delicious meal.
    What kind of physical theories offer us insights into the physical nature of the world? Well, a standard-looking fundamental theory will do. Classical mechanics is a good example. It has an inventory of what exists concretely (particles) in a space-time structure and dynamical laws of motion that govern the behavior of particles. But what really exist according to quantum mechanics? Some people would remember an answer from their first college physics class — collections of things that are both particles and waves (or maybe neither particles nor waves, depending on the class instructor). But if you ask them to point to the physical theory for the mathematical formulation of such things, they probably can’t give a clear answer. To be sure, this by no means is their fault. Many of their instructors believe that it’s impossible to precisely spell out a consistent and intuitive idea of what exist in a quantum world. 
    Does it mean that we can’t understand the quantum world? Far from it. There are adequate and coherent quantum theories that say precisely what exist. For example, Bohmian mechanics has particles, GRWf has flashes, GRWm has mass densities, and the Many-Worlds theory can also be coupled with a mass density ontology.
    However, as Professor Halvorson points out, in all these theories, we still wonder what the nature of the wave function can be. Some people take it to be a statistical tool giving us statistical information about an ensemble of systems. The recent PBR theorem shows the untenability of such a position. Other people take the wave function to correspond to something real, physical, and objective. (Maybe there are plausible middle positions.) One paragraph in Professor Halvorson’s article seems to suggest that thinking of the wave function as real and physical naturally leads one to think of the wave function a ”thing” and to think that is to commit a categorical mistake, because the wave function is a state; as a state it is more like a situation, not itself a property-bearer but composed of property-bearers. Let me try to address these worries. First, situations, even if they are more abstract than concrete things, can still bear properties, such as being consistent, maximally complete, containing individuals, and standing in certain relations to other situations. Second, thinking of the wave function as a concrete thing is not a grammatical confusion. Since the wave function is intimately related to how concrete things move in the 3-dimensional space, by pushing the particles (Bohmian mechanics), generating collapse flashes (GRWf), shaping the mass density (GRWm and Many-Worlds with mass density), it enters into a dynamical causal relation analogous to the classical electro-magnetic field’s action on charged particles. (Electro-magntic fields can also be thought of as both physical states and concrete things.) Moreover, it has its own dynamics of evolution (the Schrodinger equation). Finally, there are many other open options to interpret the wave function in a realist way:
    (I) as something like a physical law, a nomological or quasi-nomological object (proposed initially by Durr, Goldstein, and Zanghi),(II) a Humean law that best summarizes the particle facts (proposed by Elizabeth Miller, Michael Esfeld, Zee Perry and Harjit Bhogal),(III) a sui generis entity in its own ontological category (proposed by Tim Maudlin), (IV) a ”multi-field” living in our familiar 3-dimensional world that assigns values to every N-tuple of points (discussed by Peter Forrest and Gordon Belot).(V) a field living in the high-dimensional space (dimensions = 3 times the total number of particles) (proposed in some papers of J. S. Bell, and later developed by David Albert and Barry Loewer).
    There is a lively debate going on in  philosophy of physics and metaphysics  about exactly this topic, i.e. which of the five (and maybe more) options is the best way to understand the nature of the wave function and its implication for the space-time structure. 
    Regardless which one is the true view of the wave function, I agree with what Professor Halvorson mentions in the last part in his article: the wave function and the character of quantum mechanics leads to certain limits to what we can in principle know about the physical world. For example, according to Bohmian mechanics (the ”absolute uncertainty”), we cannot know about the physical system beyond what’s given to us by the Born rule (the squared amplitude of the wave function); according to GRW, we cannot reliably measure the number of wave function collapses a physical system undergoes in a given time interval. Charles Wesley Cowan and Roderich Tumulka give a list of 11 examples of limitation of our knowledge in quantum mechanics. (http://arxiv.org/pdf/1307.0827.pdf
    To be sure, do these examples show that the quantum world is far from our perceptions of the world? Well, if we mean that there is a gap between the objective facts and the empirically knowable facts, then yes—they do. But if we mean that there is a gap between the objective facts and what our fundamental physical theory describes, then I am less sure that the quantum phenomena and the quantum formalisms demonstrate that.  
    I realize my comment has become very long. So a last and brief remark. What is really surprising in quantum mechanics, I think, is quantum non-locality, as manifested in the entanglement state. It is surprising because it is independent from the spatial arrangement of the particles. 

  7. Eddy Chen says:

    Just a follow-up on my previous comment. Professor Halvorson reports one rationale for departure from realism is ”quantum indeterminacy.” He writes, ”Quantum indeterminacy is the unavoidable fact that not all quantities can simultaneously have determinate values.” it might be helpful to discuss a little about naive realism about operators and the role of measurement in a comprehensive physical theory of the world. Basically, the problem about unable to simultaneously  assign determinate values dissolve itself if we give up the idea that there is a one-to-one correspondence between the mathematically defined operators in quantum mechanics and real quantities in the world. Why not think that physical experiments, instead of revealing fundamental pre-existing values, take part in creating them (from the positions of particles to pointer readings)? 

    • Hans Halvorson says:

      Thanks to Eddy for all the great points he made, and for reminding us of all the work that has been done to find suitable realistic interpretations of QM (by physicists such as Goldstein, Tumulka, etc.). 

      I’d like to take up a few of Eddy’s points. 

      1. “What kind of physical theories offer us insights into the physical nature of the world? Well, a standard-looking fundamental theory will do.”  I agree with this comment.  In fact, I’m willing to ask for something even more modest: if somebody proposes a physical theory, they should say (a) what things exist, and (b) what properties they have.  Orthodox QM already fails those ultra-modest criteria.  Does the Everett interpretation do any better?
      2. “Does it mean that we can’t understand the quantum world? Far from it. There are adequate and coherent quantum theories that say precisely what exist. For example, Bohmian mechanics has particles, GRWf has flashes, GRWm has mass densities, and the Many-Worlds theory can also be coupled with a mass density ontology.”  These interpretations offer some advance in our understanding — but I contest the claim that they remove all mysteries.  Bohmian mechanics says that particles exist … but what does it say about the wave function?  Here it stretches our comprehension, because it seems that the wave function does exist, but not in the same way that particles exist.  Are there really two different ways of existing?  What does that mean?  I’m also skeptical of mass-density interpretations of the wave function.
      3. “thinking of the wave function as a concrete thing is not a grammatical confusion.”  I’m not convinced.  If the wave function is a thing, then it must have properties.  But what are its properties?  It won’t do to say something like: it’s a function, and it’s properties are just the properties of the function.
      4. “Basically, the problem about unable to simultaneously assign determinate values dissolve itself if we give up the idea that there is a one-to-one correspondence between the mathematically defined operators in quantum mechanics and real quantities in the world.”  There are good reasons for thinking that for each operator O, there is some corresponding feature of reality.  The reason is: we can measure O and get reliable (repeatable) outcomes.  Now, I grant that it is perfectly coherent to take the Bohmian stance that this evidence — the reliability of O measurements — is misleading; that really there is no fundamental quantity that is represented by O.  Perhaps that is one of the lessons of QM.  But then the lesson is precisely that appearances are misleading.  
      5. “What is really surprising in quantum mechanics, I think, is quantum non-locality, as manifested in the entanglement state.”  I think that QM is already surprising before we consider quantum non-locality.  For example, consider a universe in which there is a single particle that obeys the laws of quantum mechanics.  That particle already has the feature that it cannot simultaneously have determinate position and momentum, which I find surprising (relative to classical intuitions).  What’s more, a single particle can have entangled degrees of freedom — e.g. its spin could be entangled with its position.  And this means that entanglement doesn’t imply non-locality.  I think it oversimplifies issues to say something like, “non-locality is the distinctive feature of quantum mechanics.”  (Eddy didn’t say that, and I’m not attributing it to him.  But I’ve heard other people say it!)    
      • Eddy Chen says:

        Re 2 and 3: Thanks to Professor Halvorson for his nice comments and questions. In the following I shall mainly address his comments #2 and #3. I agree that to be a realist about the wave function (just like being a realist about almost anything in the physical theory) takes some arguments. Let me first clarify what I have in mind about the structure of a physical theory. Roughly speaking, there are two kinds of things that exist in a realist fundamental physical theory. (1) There are things in the physical theory that directly make contact with the evidence (pointer readings are such and so because of the arrangement of the particles, or the position of the flash, or the shape of the mass density; and they are such and so because of the geometrical structure of space and time, etc). We are more easily convinced that that part of the physical theory exist concretely in the world. (2) There are other things in the physical theory that are less directly in contact with the physical evidence. But if they are not directly about our evidence, what are they doing in our physics? Well, we need them to provide a complete account of the physical world and the dynamical evolution. The wave function fits in the second category (and it’s needed to account for the interference patterns in the double slit experiment, for example). What are other examples that fit in (2)? Maybe the physical laws. In any case, being less in contact with the evidence and being less concrete doesn’t make the wave function less real–as part of the physical ontology. It’s an open question whether it’s fundamental, and one’s view on the metaphysics of law (Powers, Fundamental law, or Humean law) will influence one’s answer to that question.

        To recap, let me give an argument for taking the wave function to be a real physical thing.

        Premise 1: In the fundamental physical theory, if the dynamical equation of the fundamental physical stuff crucially involve X and X has its own dynamics, then X is a real physical thing. (Inference from the dynamics)

        Premise 2: All realist quantum theories crucially involve the wave function in the dynamics of the primitive things (particles, flashes, mass densities, etc) and the wave function obeys dynamical laws (Schrodinger equation and maybe additional stochastic jump rules).

        Conclusion: if quantum mechanics or something sufficiently nearby is the fundamental physical theory, then the wave function is a real physical thing.  

        Now the argument still leaves it open which of the 5 metaphysical accounts (nomological, Humean-nomological, sui generis entity, 3-dimesnaionl multi-field, high-dimensional field) is the right one for the wave function. To answer Professor Halvorson’s question what its properties are: depending on the specific quantum theory, it pushes the particles (Bohmian mechanics), generates flashes (GRWf), shapes the mass density (GRWm and Many-Worlds with mass density). To be sure, these sound like saying the wave function has the properties that the function has (given by the quantum theory) and tell us nothing interesting. What are its other properties independent of the dynamics of the primitive stuff? Well, it can change overtime or it can be static (depending on future research on quantum cosmology). We probably can’t see it, touch it, or trap it under a microscope, but the physical theory makes it meaningful enough to call it a real physical thing, although it may not have the same kind of existence as particles or mass densities. [Just to clarify: I use GRWm to refer to the GRW collapse theory with a mass density ontology and a wave function. The mass density changes its shape according to the wave function. It doesn’t replace the wave function in any way.] 

        It may well be that a surprising thing we learn in quantum mechanics is that the wave function–being central in the physical theory–is something that is clearly in the second category of physical things. 

        • Hans Halvorson says:

          Eddy has put forward an interesting argument for the claim that, “the wave function is a real physical thing.”  But I am worried about the first premise

          P1: If the dynamical equation of the fundamental physical stuff crucially involve X and X has its own dynamics, then X is a real physical thing.

          I think this premise would lead to unacceptable conclusions.  For example: Let X be the state of a single free particle in Newtonian mechanics.  Then the dynamical equations crucially involve X and X has its own dynamics.  So P1 would entail that X is a real physical thing. 

          But this conclusion seems bizarre.  In Newtonian mechanics, the state X of a particle is nothing more than a specification of the properties possessed by this particle.  If we ask, “how many things exist in this scenario?” the correct answer is “one.”  We shouldn’t answer, “two things exist, — a particle and its state.”  Because then we should have to ask, “what is the state of those two things?”  Then we would have three things, “the particle, its state, and the state of the particle and its state.” 

          • Eddy Chen says:

            Professor Halvorson gives an interesting example about a single particle universe to illutrate his worry about Premise 1 in my very rough argument for the physical reality of the wave function. I didn’t think through the argument to make sure it’s counterexample-proof. So I welcome this nice opportunity to think about this. Let me sketch a reply and a defense of Premise 1 in the face of this example. The single free particle in a Newtonian universe will travel with constant velocity. Since there is no interaction with other particles (the example is a single particle universe), we just need the position and the velocity of the particle at some time slice. Take the position x_k and the velocity v_k of the particle, and call their ordered pair the State_k. Is State_k a real physical thing? Given Premise 1, it is. But it doesn’t follow that State_k is a fundamental physical thing, for it’s entirely determined by the more fundamental physical things — namely the position x_k and the velocity v_k of the particle — since it’s just an ordered pair of them. (Let’s set aside the question whether sets of contingent things are contingent; we can probably just as well frame the discussion in terms of plurals or some other metaphysically neutral entities.) At any rate, fundamentally, Premise 1 is compatible with the following claims: fundamentaly there is just one particle in the above example, and fundamentally it has two properties (position and momentum) which, I guess, give rise to another physical real thing, namely the State that include both position and momentum. 

            Now, the real question, I think, is this. (Thanks for Prof Halvorson for leading us back to it.) Given Premise 1 (and suppoing the rest of the argument), is the wave function physically real in the fundamental sense or in the non-fundamental sense (being composed by some fundamental properties)? Now this goes back to the earlier question, namely, what is the metaphysical nature of the wave function–is it a (quasi-)nomological object, a Humean summary, a sui generis entity, a multi-field on the ordinary 3-space, or a field on a high dimensional configuration space? On a Humean picture, if we take the wave function to be part of the best summary of the 3-dimensional mosaic of particular facts, then we end up reducing, in some sense to be made precise, the wave function to the more fundamental properties, say, the positions of Bohmian particles. If one favors a sparser ontology, then use the spacetime points and their occupation properties to ground the wave function. At any rate, the wave function can be plausibly thought of real and physical, but its exact place in our metaphysics and its exact nature is an open and interesting question. 

          • Roger A. Sawtelle says:

            Eddy’s comment brings up an important question.

            Is something real because it is relational, or Is it relational because it is real?

            While I think that both are true, if “things” are real because they are relational (and they are), many “things” that we generally do not consider “real” are.

          • Hans Halvorson says:

            In the case of the Newtonian single-particle world, I would hesitate to say that the state is a, “real physical thing,” even a non-fundamental physical thing.  To say that the state is a non-fundamental physical thing is to treat it on analogy to, say, a tree.  But states aren’t like trees, since they aren’t composed of smaller physical objects.  (There is only one physical object in this toy universe, and so no other physical things can arise from composition of smaller things.) 

            I do think that states are both “real” and “physical.”  Consider an analogy.  My bicycle is going 15 mph.  The velocity of my bike is “real” and “physical,” but it’s not a “thing.”  If I were to take an inventory of the things in the universe, I would not include the velocity of my bike.

            So what is my criterion for being a “thing”?  Here I loosely follow W.v.O. Quine, who said that we should “regiment” our scientific theories, i.e. write them out in a clear fashion so that it becomes transparent what the predicates are, and what the quantifiers range over.   According to Quine’s standard, a “thing” is just a value of a variable in our best scientific theory.

            An interpretation of QM is really just another word for a regimentation of QM.   In a good regimentation/interpretation of QM, the variables will not range over wave functions.  But then, wave functions are not “things.”

            This grammatical point aside, I completely agree with Eddy that all the interesting philosophical work remains to be done — namely, inquiring into the wave function’s exact place in our metaphysics and its exact nature.

          • Eddy Chen says:

            Prof. Halvorson writes, ”So what is my criterion for being a “thing”?  Here I loosely follow W.v.O. Quine, who said that we should “regiment” our scientific theories, i.e. write them out in a clear fashion so that it becomes transparent what the predicates are, and what the quantifiers range over.   According to Quine’s standard, a “thing” is just a value of a variable in our best scientific theory.”

            I agree with Prof. Halvorson that individuals in our theory are physical ”things.” But I disagree that they are the only physical things in a physical theory. Certain properties, for example, can be physical things too. Consider a classical electromagnetic field. (Let’s assume substantivalism to simplify the discussion.) One way to think of its physical nature is to think of it as time-dependent source-sensitive properties of space-time points (and the properties enter into the dynamical equation of motion for charged particles). We might reasonably take these properties instantiated by space-time points to be physical things, as we might reasonably take the electromagnetic fields to be physical things. So, we can modify the Quine’s criterion to allow the logical regimentation to range over properties and include them in the category of physical ”things.”

            In non-relativistic Bohmian mechanics (and slightly less naturally in GRW and MWI with mass density ontology), for example, the state of an n-particle system at a time consists in Q and Psi, where Q is the actual positions of all the particles, and Psi is the actual wave function defined over all possible arrangement of particle positions. Here, we can take the multi-field approach and regard Psi as properties for n-tuple of spatial points. Such properties enter into the dynamical equation of motion, guiding the movements of the particles. So quantun mechanics coupled with a multi-field ontology quantify over the wave function. Therefore, the wave function is a physical thing. 

            This is probably a very flat-footed response. But I think it’s sufficient to show that it makes sense to think of the wave function as a physical thing, even given the (slightly upgraded) Quinean criterion. 

          • Hans Halvorson says:

            Eddy:  Perhaps I’m just more old-fashioned than you when it comes to ontology.  I’d like to try to maintain the old-fashioned view that the world is made out of two different kinds of things: substances, and modifications of substances (properties). 

            In your example (the classical EM field), “properties instantiated by space-time points” are just that — properties.  They aren’t substances.  If there are any substances here, they are the spacetime points, and the field values are the properties that these substances possess. 

            But then what is the ontological category of the wave function?  Is it a substance or a property? 

            I claim that the wave function not a substance.  Here is one quick argument for that claim: for any substance x, if x contingently has property P, then there is a possible world in which there are two copies of x, one of which is P, and one of which is not P.  (Why should you accept that principle?  Because substances are independent of each other.)  Thus, if the wave function of the universe x is a substance, then there is a possible world in which there are two copies of x, with different properties.  That is, in this possible world there are two “wave functions of the universe” — which is absurd.   

            So I think it makes more sense to say that the wave function is a property, not a substance.  Do you see any problems with that view, or any reason to prefer wave function substantivalism?

          • Eddy Chen says:

            Hans: Thanks for your interesting argument for the claim that the wave function is not a substance but more like a property. (I’m very sympathetic to your metaphysical picture about the substance-modification divide.) I used to think that it is an open question whether the universal wave function is a property (or collections of properties) or a subtance. But if your argument works, then it can’t be a substance.

            Let me reply to two crucial premises in your argument. Premise 1: “for any substance x, if x contingently has property P, then there is a possible world in which there are two copies of x, one of which is P, and one of which is not P.” The second premise follows from substituting x with the universal wave function and P with one of its contingent properties. But is Premise 1 true? I think not. Substitute x with our universe. Doesn’t this instance of Premise 1 lead to troubles? Alternatively, substitute x with some contingent substance and substitute P with the property of existence. Doesn’t this instance of Premise 1 lead to more troubles? 

            For the sake of the argument, let us grant that Premise 1 is true. Follow Premise 2 and conclude that there is a possible world in which there are two copies of the universal wave function, with different properties. Is it absurd? I think not. Here are two reasons.

            (1) Wave functions can superpose. Take the actual wave function Psi_A and modify it (in a mathematically nice way) to Psi_B. Go to another world W, superpose Psi_A and Psi_B and get Psi_C. Psi_C can be the universal wave function of W. Psi_A and Psi_B will still be wave functions, although they are not the wave functions of the universe, for it’s Psi_C that will contain all the dynamical information. Is there a contradiction? I don’t think so. Psi_A is, in the actual world, the wave function of the universe. But since that description is not a rigid designator, it can have different referents across worlds. So in world W, ”the wave function of the universe” refers only to Psi_C, not Psi_A or Psi_B.

            (2) Start with the actual wave function Psi_A. Modify it nicely to Psi_B. Go to another possible world S. In S, there can be two disconnected universes A and B, governed by Psi_A and Psi_B respectively. Thus, in S, the description ”the wave function of the universe” is ambiguous. Depending on the resolution, we either refer to Psi_A or Psi_B. (To be sure, we can do something more fancy and use the description ”the wave function of the possible world.” But I’m sure we don’t want to go there.)

          • Hans Halvorson says:

            Eddy: Thanks for your contributions — you’ve given us a lot to think about.   Let me try one thing in defense of Premise 1 (in my argument that the wave function is not a substance).   You mention the universe as a potential counterexample.  But I would say that the universe is the totality of all things — and cannot be counted as a thing itself.  If the universe were a thing, then there would be another thing that contains the universe, namely the set that contains both the universe and all things in it.  Similarly, when we count the things that exist in a possible world, we don’t count that possible world itself.  (The domain of quantification is not one of the objects that we quantify over.)

          • Roger A. Sawtelle says:

            Prof. Halvorson wrote:

            I do think that states are both “real” and “physical.”  Consider an analogy.  My bicycle is going 15 mph.  The velocity of my bike is “real” and “physical,” but it’s not a “thing.” 

            I agree that velocity is real, but how is it physical.  It is part of our universe, but it is not energy/matter.  Velocity is time/space, which is relational,and thus “real,” but not physical. 

             Granted the best known equation in physics includes velocity but that does not make velocity physical.  The best known equation makes physics relational and more than pohysical. 

            When we began this discussion you said that your wife was not a robot, meaning I believe that she is more than physical.  Certainly your wife is physical, so she must be more than physical, rather than less than physical.

            I would propose that the primary reasons why your wife is more than physical is because the universe is more than physical.  The universe is not only composed of matter/energy, but also time/space, which is not physical, and meaning/purpose, which is not physical. 

            Humans live in (at least) three overlapping worlds, the world of the physical, the world of the rational, and the world of meaning.  We can study them separately, but they are not separate, and when we look at the world in terms of philosophy, which is synthetic, rather than reductionist, we must take this into account.   

  8. ianful says:

    Let us not forget that quantum mechanics, as well as mathematics and the over-arching disciplne of science is but a model of reality constructed by human minds. It needs only to work for us as far as our capabilities as humans are concerned and nothing more. Our perceptions and understanding are tied to what we have devised, and we increase these in a somewhat cyclic loop. Time and space seem to be mankind’s major preoccupation.

  9. abed.peerally says:

    According to Chen the wave function is a real physical thing. First of all we cannot be so sure about it for at our most elementary level there has to exist something which as the author has indicated represenst a state of being which precedes the organised strucutures like atoms. This is a sine qua non concept if we really hope to elucidate our origin at its earliest and most fundamental stages.The simplest we have so far is the wave function and it is not unreasonable to regard it as a state of being. I have reasons to believe that it is a second order state of creation, a first order state of being,  which emanates from the first order precreation reality which I will in due course describe,.I see how this state of first order of being arose from the first order fuzzty state which cannot at all be described as a physical reality for it existed before photons and gravitation  had their first existence. There is a great deal of sense to believe that there was an act of creation from a superintelligent mind bent on producing a universe with the extraordinary structure and composition we know in addition to our natuyral laws. Quantum mechanics is not our most fundamental physical concept and therefore the wave function too is not our most basic state of being.. There is a more fundamental concept and entity of higher scientiic order for clearly both QM and the wave function cannot on their own elucidate the nature of our various realities including consciousness. We will see that our universe has a fabulous metaphysical (also scientific) origin where there existed what was needed to produce matter and consciousness and the inexorable entropy, which pushes the universe towards its ultimate destiny in  the very distant future

    Regarding Ianful’s comment I think that scientific project is not a myth but the deepest reality of what we are but still very incomplete and we are moving in the direction of knowing our ultimate origin and what our realities mean.

    • Eddy Chen says:

      Dear abed.peerally, thanks for your kind comment. You mentioned that (1) there are other things that QM and our current scientific theory cannot explain, e.g. consciousness, and (2) there may be an ultimate explainer of everything (e.g. a superintelligent designer). I think one can hold (1), (2), and still ask this: what does quantum mechanics tell us about the physical reality? Granting that there can be other equally fundamental things or more fundamental things, e.g. minds, and granting that there can be an ultimate agent who explains everything, we can still inquire into the physical nature of the central object of quantum mechanics, namely the wave function. (If God determines the physical laws, then the physical laws are going to include the Schrodinger equation in quantum mechanics, for all we know, and the central dynamical object is going to be the wve function.) The wave function doesn’t need to be fundamental, i.e. being the bedrock of the world, to warrant our analysis. In so far as such analysis is warranted, we can discuss and disagree about the physical nature of the wave function and whether quantum mechanics suggests that the physical domain contains radical indeterminacy, etc. Hope this helps. 

  10. Roger A. Sawtelle says:

    Dr. Halvorson states that a state is not a thing, but a way of being; and reality is a wave function.   

    He says that there is no disconnect between the quantum world which is subatomic and the macroworld which is atomic and above.  I believe that the evidence indicates otherwise. 

       The fact of the matter is humans live in the macroworld of atoms and molecules.  Water to take a wonderful example comes in many forms and has many qualities and there is no evidence that these are based on different wave functions.  On the other hand these is good evidence that the forms water takes is based on it’s chemical form, 2 atoms of hydrogen and one atom of oxygen bound into a complex/one molecule.

    The “nature” of water is determined by the chemical natural physical form which H2O takes.  Sub atomic particles may be waves, but molecles are things, just as perhaps three atoms of gas unite through oxidation to become a liquid at room temperature.    

    What is real?  Is the internet real?  Is politics real?  Scientists tend to look at science is real and of course it is, but humans live in many other worlds besides the world of science or the world of nature.  In fact we live primarily in many human worlds which has there own laws and ways of doing things.

    We life in many worlds where the laws of which are all different and not universal.  We live in a complex and diverse world where there are different ways to do things.  There is more than one way to skin a cat, my father, trained to be an engineer, used to say.

    Dr. Halvorson looks for answers through physics in the vertical, from the bottom up.  Another way is to look horizonally to see how events and persons on the same plane interact with each other.  Another way to study something is from the top down.  In my opinion rthe bast way to examine something is from as many perspectives as possible.

           I call this relational thinking and I note that the Stamford Encyclopedia of Philosophy online has an article entitled Relational Quantum Mechanics (Fall, 2008) which says that the quantum world is relational.  I quite agree.        




    • Eddy Chen says:

      Dear Roger A. Sawtelle, your idea about the relational way of thinking sounds very interesting and I had a quick look at Laudisa and Rovelli’s SEP article on Relational Quantum Metaphysics. Unfortunately I don’t quite understand that approach. Could you say more about it and how does it relate to the issue about the wave function and perceiving reality? 

      • Roger A. Sawtelle says:

        Dear Eddy Chen,

        Thank you for your response.

        I will try to answer your question, but I am not sure where to start, so I will begin at the beginning.

        Relational metaphysics as I understand it, is based on the fact that existence is relational.  This is different from traditional metephysics which says that existence is based on being, which is not relational.  If existence is relational, then reality must be complex.  Entities must relate to at least another entity to exist or entities must be conplex in order to relate to itself. 

         However existence must also be one, because entities cannot relate to or interact with other entities unless they have sumething in common.  Thus Relational Metaphysics sees reality as being complex/one, both in terms of the whole and individual aspect of reality.

        Now you want me to speak on the question of wave function and perception.  Please excuse me but I am not a physicist by training, as if you haven’t guessed, so I want to make sure I understand your question.  I take it you are speaking in the quantum context. 

        First, it seems to me that physics has resolved the particle/wave duality of matter/energy into a wave at least in the quantum situation.  I do not think that this is the best approach.  I think that it is best to say that matter/energy acts like wave in some situations and a particle in others. 

         In any case Relational Metaphysics recognizes that the quantum world is very different from the macroworld, because a) sub atomic particles are different from atomic and beyond entities.  b) The quantum is governed primarily by the strong force, while the macro world is governed primarily by the weak gravitational force.  c) Since time and space are relational rather than absolute, and the microworld is difference from the macroworld, time and space in the quantum must be different.

          Now while Relational Metaphysics allows for diversity within reality, it also calls for unity within reality.  The problem with other theories is that there is unity or diversity, not both.  This where Noether’s Theorem comes in.  It allows unity in diversity through symmetry and broken symmetry. 

         The question about wave function and perceiving reality.  First of all, I would say that the scientific quest to see the Face of God by discover a basic particle that solves all our problems isw wrong headed.  On the other hand if science would come to the conclusion that the basic structure of Reality is Complex/One as I have indicated this would be an excellent step in working out our problems together with others.

         Second, Humans are able to perceive subatomic particles because they relate within time/space to other particles and atoms.  We know that they have velocity, which is relational.  We know that they have location which is relational.  We just do not know both at the same time, which could be because time and space are different in that world from ours.  This also might explain entanglement.

          Finally if wave function is another same for wave form.  I can go along with that.  In Relational Metaphysics function follows form, rather than the other way around.  We perceive a given thing because we perceive its form whether its is a person, an idea, music, light, or a particle.

        Excuse for the length and the strangness of these thoughts, but I hope this does answer your question.

        Please ask if you have any questions, as I am sure you do.  Thank you for your curiousity and patience.


  11. abed.peerally says:

    I totally with this part of the remark make by Chen in his last comment:

    “but its exact place in our metaphysics and its exact nature is an open and interesting question”.

  12. abed.peerally says:

    I totally with this part of the remark make by Chen in his last comment:

    “but its exact place in our metaphysics and its exact nature is an open and interesting question”.

  13. hussain.hussainsha says:

    electron is a magnetic monopole traveling with the speed of light. At the speed of light electron behaves as magnetic monopole. this is the main secret behind strange nature of quantum mechenics. 

  14. suefein says:

    The author sets up the straw-men Bohm and Everett whom, in my opinion are so easy to knock down. Bohmian mechanics was long ago disqualified by John Bell who proved theoretcially (and was proved later experimentally) that there are no ‘hidden variables’ which Bohn used to circumvent the EPR paradox. it seems to be comong back into fashion, I have not idea why. 

    Similarly the Everettian approach tries to solve the problem of the collapse of the wave function upon observence of a quantum object. But one has to believe that this is a problem, which I don’t. Von Neumann introduced this as a problem and theorists have been struggling with it since. For example in the laborious ‘no cloning’ approach. If the collapse of the wave function is not considered a problem, or whether it is an xiom fo QM or is derived. Then the whole issue of the wave function of the universe fades into the background. the world of quantum partiucles is indded rather different from what one can observe with one’s five senses, but not in the way that this article suggests.

    • Eddy Chen says:

      Dear suefein: Prof. Hans Halvorson’s article is not trying to knocking down Bohm and Everett, and neither are they straw men. John S. Bell’s important inequality and the subsequent empirical violations do not disqualify Bohmian mechanics, for it is explicity non-local. Just recall that how the Bohmian wave function is defined. Everettian Many-Worlds theory is an honest attempt to solve the measurement problem. If you read J. S. Bell’s Against Measurement, I’m sure you can appreciate why the measurement problem is a real problem, which probably threatens the consistency of quantum mechanics. I take Prof. Halvorson to say that even if we adopt the Bohmian approach or the Everettian approach, there are still mysteries in the respective quantum theories, and there are still certain gaps between our perceptions of reality and what the quantum theories tell us. That, I believe, is where Prof. Halvorson’s article ends and where the discussion starts. What is, for example, the nature of the quantum wave function and how does it relate to the ordinary experiences we have? 

      • suefein says:

        Thank you Eddy for your relevant comment. I have read John Bell’s Against Measurement a number of times. In fact I was thinking of writing a popular science article about his “shifty split” however I am too busy to do that at the moment. It is not clear to me why anyone should expect the quantum wave function to relate to ordinary experience any more than we should expect electrons or protons to relate to ordinary experience. The public has heard about electrons and protons to such an extent that they may think that they are part of ordinary experience. Of course they are not. Needless to say, the wave function is more abstract a concept than a proton or electron as they are represented in popular articles. and can not as nicely be “dumbed down”.

        A wave function represents rhe probability density of a particle, for instance, being somewhere, such as near a detector. Bell himself was unhappy with this and proposed a possible solution called a GRW type theory which would predict the density of “stuff”. To the best of my knowledge, the GRW theory has not been followed up as he suggested to solve the wavefunction probability density problem. And there is probably some good reason why.

        Being a great fan of John Bell’s intuition of the nature of Physics and Physics experiments, 

      • Roger A. Sawtelle says:

        Dear Eddy Chen,

         What is, for example, the nature of the quantum wave function and how does it relate to the ordinary experiences we have? 

        This is the question as you say that has been raised.  Suefein and I are saying that that the rules of quantum physics have little or no impact on our ordinary experience of our world.  Why?   Because humans do not live in the microworld of quantum physics, but in the macroworld of Einsteinian physics.

         Prof. Halvorson made it clear from the beginning that he thought that the rules of quantum physics, Shroedinger’s equations, appled to the macroworld as well as the quantum world.  I think that this has less to do with physics and more to do with ontology.  The rules of traditional philosophy do not allow for more than one real world.    

        I pointed out that the quantum world is governed primarily by the nuclear strong force, while the macro world was governed primarily by the gravitational weak force.  We can see that nature of subatomic particles is different from atoms and molecules.  It follows that quantum time and space are different from macro time and space, because Reality as we know it is relational. 

        Thus measurement involving time and space in the quantum world is very different from that in the macro world.  Traditional mataphysics says that the macro world is governed or determined by the microworld.  If they are two separate worlds, governed by two sets of rules, which they seem to be, that is not true.

        The macroworld is built on the microworld, but it is not determined by it.  This is a blow to materialists and to physicists, but it is the truth.  However this is primarily a blow to traditional philosophy which is based on Being, rather than Relationships, and is the cause of the confusion that prompts this question. 

        I hope that this discussion does not get cut off prematurely by a fast approaching artificial deadline.

  15. suefein says:

    This is an addition to my original comment, which I only learned afterwards was going to be reviewed.

    I just wanted to clarify an important point about the Bohmian expressions for quantum mechanics. Supposedly Bohn had achieved what Einstein required in that he expressed QM in term of “hidden variables”. However it has been proved that Bohm’s hidden variables can not be local. That being the case, they do not satisfy the requirement of being deterministic variables of the classical mechanical type for portraying quantum events, so vainly desired by Einstein..

    And, in another addition  , I would like to mention that when a quantum mechanical particle is “detected”, it’s equation of state simply becomes entangled with the detector’s equation of state. Such a system is much too complex for meaningful quantum mechanical expression.  But the difficulty in expressing the wave function of electron+detector does not mean that an expression for the wave function of the universe must be invoked. 

    Scientists have not yet succeeded in producing cold fusion in a laboratory. But this lack does not evoke all kinds of hand-waving similar to that induced by the difficulty of expressing the wave function of electron + detector.

    I hope I have expressed myself more clearly.  Thank you.

  16. abed.peerally says:

    Quoting from Halvorson latest remark:

    But I would say that the universe is the totality of all things — and cannot be counted as a thing itself.  If the universe were a thing, then there would be another thing that contains the universe, namely the set that contains both the universe and all things in it

    I believe I could have the same fate as Bell for his paper was published in an obscure journal. Re the last comment by Halvorson which has been very categorically expressed. In my deepest of scientific opinion the universe is a subset of something which is philosophically and scietifically a greater reality. I am not speaking about a mind or God. It is not possible that such an incredibly and colossally structured thing could be totally independent of some other structure which is simply a greater reality.

    • Hans Halvorson says:

      Dear abed.peerally,  I don’t think that we disagree.  I was only warning against speaking of the totality of all things as if it were also a thing.  For doing that runs the danger of set-theoretic paradox.  I have no problem with the idea that the physical universe is only a part of a larger whole.

  17. Roger A. Sawtelle says:

    Einstein is famously quote as saying, “The most incomprehesible thing about the universve is is comprehensibility.”  This is actually a paraphrase, but it is still true.  The discusion is based on the question is Reality real or subjective? with the followup, do we live in a determinate or indeterminate Reality?

    I would suggest that Reality is both real and subjective, both determinate and indeterminate, because these are false dichotomies set up by the Western dualistic model of reality which does understand the true nature of existence.

     Humans are able to comprehend the universe because the universe is basically relational and our minds are relational.  We can therefore build relational models for a relational world in our minds which allowed us to comprehend what is going on in both natural world(s) and human world(s).  

    A world is a place that is governed by it own rational ralationships, like an ecological niche.  It had internal relationships which govern the physical, floral, and animal partipants of that niche.  It also has wxternal re4lationships that govern how that niche relate to the world in general and neighboring niches.  All of these relationships determine the existence of the inhabitants of the niche and how we comprehend what they are. 

      The quantum, subatomic world is an important aspect of reality with its own constituents- subatomic particles, its own environment- the strong nuclear force, and because it is relational, its own space and time based on these relaities.  Because the quantum world is relational just as humans and the macroworld are relational, we can perceive to some extent how it works, even though it takes special tools to do this.  Yet we should not expect the quantum world to be like our world because it is different relationally.       



  18. abed.peerally says:

    Thanks Hans for making the totality issue clear. I agree with you. At creation of the universe there was an additional very critical physical and philosophical reality. I see not other physical which we humans could understand beyond that points. In terms of metaphysical realities beyond our understanding there might well be a vast ocean but I dont think we can do any meaningful propositions maybe because our history of science and knowledge is still in its infancy. Just consider that a few years before Einstein published his Brownian motion paper the world was not sure that atoms and molecutes existed. Some even declared that the belief in particles in the fabric of nature was pure fantasy.

  19. Nicolaidis says:

    Prof. Halvorson gave us a full description of the “quantum weirdness”. In his introductory text he opted for those solutions, where reality is expanded or redefined in order to accommodate the quantum facts.

    In another direction it was noticed, as early as 1936, by Neumann and Birkhoff  that the quantum real needs a non-Boolean logical structure. Thus we have to abandon the Aristotelian logic and turn into a novel system of logical syntax. Recently we have suggested [A. Nicolaidis, Categorical Foundation of Quantum Mechanics and String Theory, Int. J. Mod. Phys. A24: 1175-1183, 2009] that the relational logic of Charles Sanders Peirce, the founder of American pragmatism, may serve as the conceptual foundation of Quantum Mechanics. Within this relational architecture, the notion of a thing as a thing does not exist. A thing does exist to the extent that it is related to other things and the ensemble of these relations defines thing’s existence.

                We should view Quantum Mechanics as a “laboratory philosophy” and accept the invitation to reinvent the meaning of concepts and their operational implications.


    Argyris Nicolaidis

    Aristotle University of Thessaloniki