Qualia/Zombie Scenarios and Schrödinger’s Cat: Analogous Thought-Experiments?

The philosopher David Chalmers once discussed Erwin Schrödinger’s well-known thought-experiment. Chalmers did so in order to compare what he himself is doing to what Schrödinger did way back in 1935. More specifically, Chalmers compared his qualia and zombie “scenarios” to Schrödinger’s cat. He argued that they too “bring out various plausibilities and implausibilities”.

(i) Introduction

(ii) David Chalmers on Schrödinger’s Cat

(iii) Chalmers’ Thought-Experiments (or “Scenarios”)

(iv) David Chalmers on Conceivability

(v) Schrödinger’s Cat Again

Could David Chalmers’ qualia and zombie scenarios even become part of any flesh-and-blood experiments? In more basic terms, should Chalmers use the word “experiment” about his own qualia and zombie scenarios at all?…

Yes!

A thought-experiment isn’t a physical or concrete experiment — the clue is in the name. And Chalmers himself stresses the fact that his primary concern is “conceptual possibility” (or “conceivability”), not flesh-and-blood experimentation…

Yes, Chalmers is a philosopher, not a scientist.

All that said, Erwin Schrödinger’s own thought-experiment never became an actual experiment either. In other words, it has never been carried out on a cat or on any other “classical” object. That said, successful experiments involving superpositions of “relatively large objects” have been performed. (Relatively large, but not even the size of a neuron.) [See note 1.]

So what did Chalmers have to say about Schrödinger’s Cat?

David Chalmers on Schrödinger’s Cat

Chalmers wrote:

“Perhaps it is useful to see these [zombie an qualia] thought-experiments as playing a role analogous to that played by the ‘Schrodinger’s cat’ thought-experiment in the interpretation of quantum mechanics.”

Chalmers then explained this analogous role in the following way:

“Schrödinger’s thought-experiment does not deliver a decisive verdict in favour of one interpretation or another, but it brings out various plausibilities and implausibilities in the interpretations, and it is something that every interpretation must ultimately come to grips with.”

Chalmers finally concluded:

“In a similar way, any theory of consciousness must ultimately come to grips with the fading and dancing qualia scenarios, and some will handle them better than others. In this way, the virtues and drawbacks of various theories are clarified.”

In this case at least, Schrödinger’s thought-experiment about a cat was deemed by Chalmers to be “analogous” to his own qualia and zombie “scenarios”. Yet, prima facie, it’s hard to spot anything analogous here other than that all these examples are… well, thought-experiments.

Chalmers’ Thought-Experiments

David Chalmers isn’t naïve about the arguments against his own modal theorising. For example, way back in 1995, Chalmers once happily stated the following:

“The mere logical or metaphysical possibility of absent qualia is compatible with the claim that in the actual world [there is no such thing]. [ ] Mere intelligibility does not bear on this, any more than the intelligibility of a world without relativity can falsify Einstein’s theory.”

Yet, as we’ll see in a moment, “logical or metaphysical possibility” is still very important to Chalmers — despite his prefix “mere”.

What’s more, elsewhere in the same paper Chalmers wrote:

“But it is implausible that fading qualia are possible, and it is extremely implausible that dancing qualia are possible. It is therefore extremely implausible that absent qualia and inverted qualia are possible.”

On a positive reading, it can be argued that it was right and proper that these possibilities (or though-experiments) be considered — even if, in the end, they were ruled out for the “actual world”. After all, how can we rule these possibilities out (or in) unless we firstly tackle and analyse them?

So, despite Chalmers pre-empting many of the counterarguments, logical possibilities are still fundamental to almost all his philosophical work. [See note 2.] Relevantly, some of his possibilities are ruled in, rather than ruled out.

More specifically, the philosophical notion of conceivability is at the very heart of much of Chalmers’ work.

David Chalmers on Conceivability

Without (philosophical) conceivability, Chalmers’ arguments against physicalism — and in support of the possibility of philosophical zombies, inverted qualia, dancing qualia, absent qualia, etc. — wouldn’t get off the ground in the first place.

In terms of zombies scenarios (i.e., not qualia scenarios), Chalmers himself says that

“the question is not whether it is plausible that zombies could exist in our world, or even whether the idea of a zombie is a natural one; the question is whether the notion of a zombie is conceptually coherent”.

To Chalmers, then, “the notion of a zombie” is “conceptually coherent”.

However, let the English philosopher Philip Goff put the case-for-conceivability in more technical terms.

Firstly, Goff expresses his view about the importance of conceivability (leading to possibility) in this way:

“If P is conceivably true, then P is possibly true.”

So is a cat being both alive and dead at one and the same time “conceivably true”? It depends on what, exactly, is conceived. More clearly, what is it to conceive of the same cat being both alive and dead at one and the same time?

Goff then expresses his position in possible-worlds jargon:

“If P is conceivably true (upon ideal reflection), then there is a possible world W, such that P is true at W considered as actual.”

Or, less technically, Goff actually refers to Chalmers when he says that

“Chalmers holds that every conceivably true proposition corresponds in this way to some genuine possibility”.

Thus, if it’s “conceivably true” that the same cat be both alive and dead at one and the same time, then there is a possible world W in which that cat is both alive and dead.

It’s not clear, here, how shifting this issue to a “possible world” negates the problem we have with the psychological notion of conceivability.

Oddly enough, according to many-worlds theorists, the alive cat and dead cat are indeed in two different worlds — if not in two possible worlds. That is, this superposition would actually occur in a multiworld - it’s not a (mere) possibility. (Such physicists believe that the alive-and-dead-cat superposition would be actual if the experiment were ever successfully carried out.)

Schrödinger’s Cat Again

Erwin Schrödinger himself never believed that a cat could be both alive and dead at one and the same time…

In basic terms, Schrödinger intended his thought-experiment to illustrate the bizarre nature of the Copenhagen interpretation of quantum mechanics. Indeed, Schrödinger took it to be a reductio ad absurdum.

Chalmers, too, sees himself as considering various logical possibilities, and (as it’s often put) seeing where they lead.

Oddly enough, Schrödinger can be seen as actually arguing against taking outlandish possibilities (in this case, superpositions) seriously. After all, aren’t there literally innumerable possibilities that can be — or even must be — considered? Of course, it can now be argued that some possibilities are (well) more possible than others. They may also may be more interesting, relevant, useful, scientific, etc. than others. And all that may apply to Schrödinger’s cat, as well as to Chalmers’ zombie and qualia scenarios.

Ironically enough, Schrödinger concocted a thought-experiment (which is about the logical possibility of a cat being both alive and dead) to advance his case against the possibility of a particle (i.e., not a cat) being in various superpositions within quantum experiments.

All that said, it can now be acknowledged that both Schrödinger’s and Chalmers’ thought-experiments do indeed (as Chalmers put it earlier) “bring out various plausibilities and implausibilities”. And, surely, that’s a good thing for both physics and philosophy.

Notes:

(1) Here are two examples:

“Two distinct types of experiments — both of them carried out by several groups independently — have shown that vast numbers of atoms can be placed in collective quantum states, where we can’t definitely say that the system has one set of properties or another. In one set of experiments, this meant ‘entangling’ two regions of a cloud of cold atoms to make their properties interdependent and correlated in a way that seems heedless of their spatial separation. In the other, microscopic vibrating objects were maneuvered into so-called superpositions of vibrational states. Both results are loosely analogous to the way Schrödinger’s infamous cat, while hidden away in its box, was said to be in a superposition of live and dead states.”

(2) For example, in David Chalmers’ brilliant book, The Consciousness Mind (1996), there are comments and arguments about logical possibility and conceivability on almost every page. Indeed, this was the book which jumpstarted Chalmers’ career.

Dennett Quines Qualia: A Bitter Taste Is Not a Quale

 What is it for a lemon to be “objectively bitter”? According to the philosopher Daniel Dennett (who died in April), it’s “to produce a certain effect in the members of the class of normal observers”. To Dennett, then, bitterness is a relational property. That basically means that a specific instance of a bitter taste is not a quale.

Daniel Dennett demanded that bitterness be objective (or intersubjective). And it can only be objective if it’s somehow behaviourally expressed by the class of normal observers.

Yet even if there are examples of uniform overt behaviour (such as verbal reports), do we learn anything about bitterness itself via such behavioural responses? Don’t we, instead, just learn about how people react to bitterness?

The qualiaphile argument will be that uniform reactions to bitterness aren’t themselves bitterness. So this is almost equivalent to arguing that the throwing of a ball isn’t the same as the smashing of a window. In other words, the throwing of a ball resulted in the smashing of a window, just as the tasting of something bitter leads to a certain effect in the members of the class of normal observers.

Moreover, it’s possible that the same piece of food could have a uniform “certain effect” even if it tastes differently to each person tested. Or, alternatively, something that tastes the same can have different certain effects in the class of normal observers…

So does this mean that Dennett was fusing (or conflating) cause and effect here?…

Possibly not.

How could investigators (or laypersons) know that the same piece of food tastes differently to different people, or that it tastes the same?

Dennett argued that we could only know this with the help of overt behaviour, as well as by noting physiological changes…

These standard philosophical possibilities (e.g., a piece of food having a uniform “certain effect” even if it tastes differently to each person tested) will have been rejected by Dennett simply because they’re all unscientific in nature. He might have told us that we have no way of knowing if these possibilities are ever realities. So, if that’s the case, then such possibilities are merely idle from a scientific — if not a philosophical — point of view…

But hang on a minute here.

Haven’t qualiaphiles — and many others — simply assumed that uniform reactions to bitterness aren’t themselves constitutive of what bitterness is?

What is the remainder which qualiaphiles believe is being left out?

The quale that is bitterness?

What is that?

More importantly, what is this bitter quale that is something more than the verbal reports, reactions, physiological changes, etc. of human persons?

Isn’t such a quale an example of Ludwig Wittgenstein’s own beetle-in-a-box?

Well, if the quale of bitterness is private, directly apprehensible, atomic, intrinsic (i.e., non-relational), exhaustive, ineffable, incomparable, and incorrigible, then it pretty much seems to be a beetle in a box.

[All this partly depends on whether Dennett’s characterisation of qualia — or his account of what qualiaphiles take qualia to be — is the only one available or possible. In fact, there are alternative approaches. See my ‘Did Daniel Dennett Believe that Qualia Are Real?’ in which Owen Flanagan’s alternative take on “the way things seem to us” is tackled.]

Daniel Dennett’s Wittgensteinian Position

The American philosopher Alvin I. Goldman expressed Dennett’s position on these possibilities when he says that Dennett’s

“claim is that there is no way to distinguish between these competing stories either ‘from the inside’ (by the observer himself) or ‘from the outside’, and he appears to conclude that there are no genuine facts concerning the putative phenomena experience [or differences] at all”.

This reiterates Dennett’s Wittgensteinian point that there are no facts, data… or anything available about the intrinsically private. In other words, we can know nothing of other people’s qualia — as least as qualia are seen by qualiaphiles. And, on an another Wittgensteinian theme, if we can’t know anything about other people’s qualia, then we can’t know anything about our own qualia either.

To be clear.

Qualiaphiles deem qualia to be private… things. Public language, on the other hand, is intersubjective. Yet we use a public language to communicate supposedly private qualia.

If a quale were genuinely private, then how would we know that other people were referring to the same thing which we refer to (say, the bitterness of a particular lemon)? To us (if not to them), then, other people’s qualia would be like beetles in a box. That’s partly why Ludwig Wittgenstein concluded that our language for sensations (if not qualia) isn’t only public: it must also refer to public items.

To sum up.

A particular quale (e.g., the bitterness of a lemon) can’t be a beetle in a permanently-closed box. If it’s in any kind of box, then it’s in an open and publicly-accessible one. Thus, the named “object” (i.e., the quale) must “drop out of consideration as irrelevant”.

Yes, but qualia are real!

Despite all the above, there must still be a sense that qualia are indeed private. This seems to be (literally) self-evident.

For example, if I don’t communicate my experiences of qualia with either linguistic or physical behaviour, then no one else would know that I’m experiencing the bitter taste of a lemon. However, I’m still experiencing this case of bitterness. Thus, only I know that I’m tasting a lemon which is bitter. Therefore, this bitter quale is private.

Moreover, surely there’s more to qualia than our knowledge of them. They must have both an ontological and an experiential status…

The problem is that (as Wittgenstein himself argued about sensations) as soon as we say anything about qualia (especially when using the jargon of philosophy — and the term “qualia” is itself jargon!), then they become (for other persons, and even for oneself) public things…

What’s more, this means that such things aren’t qualia at all!

Moreover, many philosophers will deem the very idea of a quale-in-itself suspect.

Does that idea even make sense?

Does it serve any purpose?

Conclusion

Yet, again, isn’t it possible that one can accept that qualia have no factual or scientific status at the very same time as accepting that they are… well, real?

It’s here that Dennett might have asked the following question:

If qualia have neither scientific nor factual status, then exactly what kind of status do they have?

What is the answer to that question?

A Pythagorean Reality: Are Quantum Systems Purely Mathematical?

 

“A quark is a purely mathematical construct. It has no meaning apart from its mathematical definition. The properties of quarks — charm, colour, strangeness — are mathematical properties that have no analogue in the macroscopic world we inhabit.”

— John Horgan [See source here.]

“[If] this electricity-field strength here in physical space corresponds to this number in the mathematical structure for example, then our external physical reality meets the definition of being a mathematical structure — indeed, that same mathematical structure.”

— Max Tegmark [See source here.]

“This mode of observing nature [i.e., mathematical physics] in an unforeseen manner vindicated the Pythagorean faith.”

— Werner Heisenberg [See source here.]

(i) The Quantum State

(ii) The Wave Function and Observables

(iii) Schrödinger’s Equation

Opening note:

I’m not a physicist, and the following isn’t a physics paper. It’s a philosophical essay about an important aspect of quantum mechanics. This means that some of the details about quantum states, the wave function, etc. may not be very sophisticated or detailed. However, hopefully that doesn’t matter too much in that this lack of sophistication doesn’t impact on the general philosophical point being made.

The Quantum State

Physics literature has it that there’s something before the wave function: the quantum state. The wave function is a “mathematical description” of that state. (More correctly, it describes “the quantum state of an isolated system”.)

Yet, as intuitively seen by a non-physicist, there seems to be some ambiguity here.

Firstly, take this account:

“In quantum physics, a quantum state is a mathematical entity that embodies the knowledge of a quantum system.”

Note the words “a quantum state is a mathematical entity” in the passage above. If readers take the word “is” as the “‘is’ of identity”, then we must have the following:

a quantum state = a mathematical entity

A quantum state is a mathematical entity. However, a mathematical entity isn’t always a quantum state. So the equation above isn’t symmetrical (or invertible).

All that said, this still means that there’s little room for interpretation here: a quantum state isn’t (to pre-empt words from the next quote) “a sub-microscopic [physical] system”.

Now take this account:

“A sub-microscopic system (a sub-atomic particle or set of sub-atomic particles moving under a force field or exerting a force on each other) is described by a ‘quantum state’ (or just ‘state’) which is a list of physical properties of the system that can be measured simultaneously.”

Note the words “a sub-atomic particle or set of sub-atomic particles moving under a force field or exerting a force on each other”.

So, in the two quoted passages above, distinctions are made between a quantum state and a quantum system. The question now is:

Is the quantum system itself mathematical?

The simple way around this is to argue that a “set of sub-atomic particles moving under a force field []” is itself a mathematical entity. Alternatively, it can be argued that the mathematical entity (i.e., the quantum state) describes such a sub-atomic system.

Perhaps this is a difference which doesn’t make a difference!

Perhaps a set of sub-atomic particles moving under a force field [ ] never has any reality (or existence) which is separable from the particular mathematical entity which describes it.

So, again, can it be argued that the mathematical entity and what it describes are one and the same thing?

[As already seen in the opening quote, Max Tegmark believes that they are one and the same thing.]

The Wave Function and Observables

The word “representation” (i.e., not the word “description” used in the quoted passage above) is often used in quantum mechanics too. [See here.] However, this time it’s used about the wave function, not the quantum state itself.

Here a given set of observables is represented. That is, the wave function represents a quantum state.

Yet surely it can’t all be about the mathematics…

Or can it?

There is a Pythagorean take on all this.

Observables

A neo-Pythagorean (or even some physicists) would say that observables (or “experimental observations”) are as mathematical as the quantum state itself. That’s primarily because observation in these quantum contexts is nothing like, say, observing the cat next door or even observing a neuron under a microscope…

One is even tempted to say, then, that the word “observable” shouldn’t be taken too literally.

In more basic terms, all talk of “observables” in quantum mechanics is replete with numbers and mathematical terms. (Such as “operator”, “gauge”, “Hilbert space”, “linear algebra”, “vectors”, etc.)

All that said, it’s clear that physicists do indeed observe many things when they carry out their experiments. The thing is, they just don’t observe (to return to the earlier terms) “particles”, “spin”, “forces”, etc. Of course, they do observe phenomena which (in a manner of speaking) point to particles, spin, forces, etc. Yet such things are still mathematical entities.

The Wave Function

Now we need an account of the wave function. Here’s one:

“In quantum physics, a wave function is a mathematical description of a quantum state of a particle as a function of momentum, time, position, and spin. The symbol used for a wave function is a Greek letter called psi, 𝚿.”

Here again (i.e., as with the previous account of a quantum state) we have the words “mathematical description”. We also have a reference to a “particle”. What’s more, the words “a quantum state of a particle” suggest that the particle itself is mathematical. After all, haven’t we already established that a quantum state is purely mathematical? Thus, a quantum state of a particle must be purely mathematical too.

So the fact that the (everyday) word “particle” is used here doesn’t seem to change that…

In addition, when readers see the words “momentum, time, position, and spin”, then they must remember that these things are mathematically described too. In other words, they’re part of the whole mathematical entity that is the wave function.

So, again, are momentum, time, position, spin, etc. purely mathematical entities? More accurately, are they the mathematical parts of a wave function which is itself a purely mathematical entity?

To recap.

We have a mathematical description (i.e., the wave function) of a mathematical entity (the quantum state), as well as references to the particles, spin, forces, etc. within a quantum system.

Let’s focus on a particle.

What kind of reality (or nature) does a particle have without either the quantum state or the wave function?

No reality (or nature)?

If we return to representation.

What Is Represented?

Surely where there’s a representation, then there must also be something which is represented.

Some quantum theorists argued that the wave function must have a physical (or “objective”) existence. [See here.] More famously, Albert Einstein argued — more generally — that a complete description of reality should refer directly to a physical time and space. [See here.]…

But hold on here!

There’s a difference between stating that the wave function itself has a physical reality, and stating that the wave function describes phenomena which have a physical reality.

Another way of putting this is to say that even though the wave function is purely mathematical (i.e., abstract), that which it represents (or describes) isn’t purely mathematical.

Now, to come at this Pythagorean puzzle from a slightly different angle, let’s bring in Schrödinger’s equation.

Schrödinger’s Equation

As with the earlier (rather basic) accounts of the quantum state and wave function, now take this account of Schrödinger’s equation:

“The Schrödinger equation is a partial differential equation that governs the wave function of a quantum-mechanical system. [ ] The Schrödinger equation gives the evolution over time of the wave function, the quantum-mechanical characterization of an isolated physical system. [ ] The equation predicted bound states of the atom in agreement with experimental observations.”

So we have the following:

Schrödinger’s equation → the wave function → quantum state → an isolated physical system

Here again, laypersons need to know if the quantum state → an isolated physical system part of the above tells us that the righthand side of this arrow is just as mathematical as everything that came before (i.e., Schrödinger’s equation and the wave function).

Firstly, physicists have the (or a) wave function, and only then do they use Schrödinger’s equation. More relevantly, this mathematical equation “describes and governs the wave function”. Yet that wave function is itself mathematical (i.e., it’s a mathematical function).

In a strong sense, then, maths is describing maths. Or, less strongly, one part of maths is describing another part of maths.

As already stated, the word “describe” is often used to explain what both the wave function and Schrödinger’s equation do — i.e., not what they are. So it’s not as if the wave function simply is what it is, and only then does Schrödinger’s equation describe and govern it. Instead, something that’s already mathematical (i.e., the wave function) is then described and governed by something else which is mathematical (i.e., Schrödinger’s equation).

Finally, the cream on this Pythagorean cake is that the “isolated system” (made up of particles, forces, etc.) which is described (or represented) is mathematical too.

So, despite the reality of observables, it’s maths all the way down when it comes to the micro-physical systems of quantum mechanics.