A quick note on aspects of physicalism and philosophy of consciousness.
The background: most philosophy contains deeply subjective opinions, it is not science, but we can apply logic and other principles we might call “rationality” of some type, to inform and correct our thinking. (This is just to say what I write is just opinion, but I am also honestly trying to gain some kind of truth about things.) When one is trained in physics, or other hard sciences, it is natural to seek a physicalist (i.e., materialist, even emergentist) explanation for the world (no need to define “the world” too precisely, it is just what we sense around us and imagine to really exist beyond ourselves and immediate senses).
Having been trained as a physicist I share these innate desires to explain the world using just physics. But nothing can proceed from absolute nothingness. So there are unexplainable things about reality that could easily be conceived to go beyond physics. The practical question is what aspects of reality can be explained by physics? The less practical (but still meaningful) question is that although no doubt things beyond the physical universe cannot be explained by physics, are there actually any such things, and if so, what the heck are they? Some metaphysical computer and meta-programmer running our universe as a simulation in their CPU? (A nice modern metaphor, but utterly facile and impractical as a basis for any useful metaphysics.)
Having said all that, the great lesson of science is that it pays to try to explain as much as possible within the confines of physics. You are not doing your mind justice if you think otherwise. However, physics is by definition a study of objective phenomena. Whenever subjective reality enters physics debate we lose the capacity to do science and aspects of the debate become philosophical, and cannot be settled unless by cordial agreement between parties! And such agreement is never universal. And to the extent it cannot be universal it is probably not scientific (science, if nothing else, seeks agreement between quasi-rational thinkers — a social aspect of science to be sure, but inescapable, science is a social phenomenon, even though the models created by science have abstract platonic “life’ of their own, independent of social thinkers.) That is why I say it is “debate” and not scientific inquiry and exploration. One can apply principles of logic and science to inform such debates, but if the subject is inherently subjective, there is no way, by definition, that physics can settle the matter. Although simplistic, the old philosophical “colour qualae” arguments suffice to illustrate what this means: colour of objects is an objective reality we can quantity with measurements of wavelengths of light, and we can objectively observe a person perhaps experience colours by gently probing their brain. But there is also a subjective aspect to the experience of what philosophers define as “colour qualae,” and of course more generally to numerous distinct categories of qualia (feelings and mental impressions of sounds, smells, abstract mathematical insights, pain, regret, joy, and all sorts).
Physics cannot ever explain the subjective aspects of such experiences. This is definitional, it is not debateable. Philosophers can argue all day about whether there are any subjective phenomena to explain, some claim there are not, so the problem dissolves, and physics can be causally complete. Others, including myself, disagree, and we think subjective mental phenomena are real, in some sense more real than any objective reality (without having to commit to Idealism).
Physicalists seek to explain such subjective phenomena reductionistically, together with emergent principles. The problem is, they can only ever (in principle!) explain the outward objective aspects associated with what the conscious person is presumably experiencing, the neural states, the behavioural response probabilities, and the like. None of this can ever be an explanation of the subjective qualae themselves, because the science is entirely objective, and ceases, by definition, to be useful science when it becomes subjective.
Now plenty of dumb philosophers (who have enormous IQ’s no doubt, and big egos) will tell you this just means qualae do not exist, they are illusions, stories the brain is somehow telling itself (but what is this “self”? — they never say, they only say ‘self’ is a collective complex system, which is no explanation for subjective experiences.).
Now that I’ve taken up all the words I originally wanted to “spend” on this post, I will cut to the chase and make my note.
Operational Non-Physicalism for Qualia
It was a thought I could not recall having read or heard anywhere else. It is one of those cringe blends of philosophy of mind and quantum mechanics, which I would normally seek to avoid like the plague (I think in general physicists have nothing more useful to say about consciousness than anyone else). But this note did seem fairly useful and important, because it is fairly simple and comprehensible and does not really employ any magical thinking or future physics speculation. The thought is that there is a way to appreciate (I am not sure if this is the right word, but let me go with it) the irreducible incorrigibility and inherently non-physical nature of consciousness. Which is by a kind of gedankenexperiment: imagining we can probe someone’s brain to gather all the necessary information to extract the subjective content (whatever that might mean) of their qualae and then transfer it to anyone else’s mind so they can experience the exact same subjective feelings — not the objective nerve impulses etc., but the raw phenomenal feel of conscious qualia. Imagining we have some maximally efficient neural probing and then transmittance apparatus that can do all this. We now have at least two, maybe three, impossible problems that physicalism cannot ever solve:
- There is still no way the subjective knowledge of “what it is like,” (q.v. Thomas Nagel) to have had the experiences of the person who is the subject here, can be objectified, can be shared, can be communicated to anyone else. We cannot hook up all people into this apparatus so they all get to know of the qualia. This is a hard measurement constraint. But it is not fatal to soft physicalism, because soft physicalism does not require that we can practically all share the qualae, it just requires that we could in principle, to whoever wants to put the receiver on their head.
- It is a fatal flaw in hard physicalism: the concept that everything is objective reality. (Soft physicalism admits there could be non-objective aspects of the world, but it is still all physics. The non-objective phenomena might be panpsychic primitives or what-have-you.). Hard physicalism entails that everything can be explained without reference to subjective observers. This is a basic foundational principle in physics. If you start admitting laws of physics depend upon observers, then you’ve lapsed into philosophy and metaphysics. It is certainty acceptable to do so, but you are then denying physicalism.
- But further, (and here is the grounded concept of this “quick note”): the mere act of probing the person’s brain and “extracting” their qualae, could be such a violent action that it destroys the useful information, leaving only the physical bits/quibits that might in principle be able to transfer the qualae impressions to a second person, but not without generating a kind of mental firewall.
The firewall here is literally a heating, a massive increase in entropy, burning up the people in the experiment if it proceeded. Anyone who knows a bit about engineering can appreciate the concept: all information processing produces waste heat unless it is perfectly reversible. But the laws of physics do permit perfect reversibility, this is just equivalent to no information loss. The thermodynamic irreversibility in classical physical processes is a kind of entropy increase, a loss of accessible information, not a loss of fundamental information. The so-called irreversible process are thus only irreversible in the sense they are so darn complicated to actually reverse them would require an enormous amount of energy input (or technically, negative entropy), meaning if one does not want to destroy the surrounding system, a massive amount of waste heat has to be dumped somewhere cool.
Note there is no paradox here. If a firewall forms because you are trying to exceed information processing capacity of the universe, you will be prevented from carrying out the process. You are operationally prevented one way or another.
The qualia transfer firewall is of course only a conjecture. It is also heavily drawing upon some quantum gravity analogies, which I do not intend to be anything but analogies!
A Diversion on Information Loss
Let me spell these out a bit. First, the idea an experiment has to be so invasive that it disrupts the system, so that precise information cannot be obtained, is a universally accepted aspect of quantum mechanics. Heisenberg’s uncertainty principle. There is no way around it. The question is whether something analogous might apply to efforts to do such mind reading? If so, then even soft physicalism would be not the metaphysics of our world.
Remember, we are not talking here about conventional mind reading, the type of thing where objective knowledge of “what someone else is thinking or dreaming” can be gained, by either hypnosis, psychology, or otherwise. That sort of knowledge is objective and utterly uncontroversial, it should be possible to do such mind reading routinely to some extent in the future. It is no different than asking someone what they are thinking, and then them giving you an honest reply in speech or writing or however.
The second thing to note, is the firewall analogy. Firewalls of this type derive from black hole physics. The rough idea (for I want to be succinct) is that in order to extract information from the Hawking radiation evaporated off a black hole (in order to preserve the laws of physics, no less) many theorists presume a firewall would form at the horizon of a black hole, burning to a crisp any objects falling inwards. The paradox is that this violates another deep law of physics: Einstein’s equivalence principle, and/or black hole complementarity. A distant observer, say Alice, sees her friend Bob falling into the black hole, but she never sees him cross the horizon due to time dilation, while Bob himself does find himself falling in, totally, and eventually hitting the singularity. These two views are consistent because of complementarity: Alice can say Bob never fell in, and his state is preserved on the horizon, albeit scrambled, but she also knows physics and thus would agree that Bob should see himself fall in. No contradiction. She just never sees the light from Bob once he falls in, which is just a banal physical constraint, not an information paradox.
The first leg of the paradox is that when the black hole evaporates, all the information about Bob would seem to be lost, since thermal radiation is supposed to be random. The second leg is that physics would not be possible if the information is actually lost, so the Hawking radiation cannot be random and has to be correlated with the information that fell into the black hole. The third leg is highly technical and takes dense mathematics of quantum field theory to explain, but the gist of it is that if the Hawking radiation is correlated with all the information that fell into the black hole, at some point, roughly when half the black hole has evaporated, there must be such a high temperature at the horizon that a firewall is unavoidable. And this clearly appears to violate complementarity, which says that in-falling observers are unharmed, they just “see” a smooth horizon and nothing strange, except the gravitational tug of the black hole and the tidal distortion effects (which produce some weird lensing effects, but totally expected if the person is a physicist who has studied general relativity!).
The resolution of this paradox which seems most generic, and plausible, has come from quantum information complexity theory, and is the (mathematically pretty rigorous) idea that the information is not lost, and a firewall does not form; but that if any outside observer had the computing capacity to ever retrieve all the information, to do so, they would have to perform such complicated probing of the black hole horizon that they would find they would be unable to avoid forming a firewall at the horizon. But it is their act of trying to retrieve the information from all the Hawking radiation which creates the firewall. If they leave well enough alone, then no firewall is formed, and physics is safe from paradoxes.
The very interesting (I’d say awesome and fascinating) thing about this resolution is that Alice can perform the measurement on the outgoing Hawking radiation far from the black hole (well after it has evaporated) but to extract the information she still needs to have set-up conditions in the past which would create the firewall and fry Bob to a crisp. This is no paradox, because now even Bob agrees he is burned up! It is Alice’s damn fault now. She should have left Bob alone to fall into oblivion.
(If they do perform the measurements, then there is again no paradox, since all observers would agree if Alice does make the measurements then a firewall does form.)
The awesome thing about this is the way in which the laws of physics permit Alice to in principle retrieve the information. She must make use of entanglement between outgoing Hawking radiation (photons) and the in-falling photons comprising the information sucked into the black hole (but by complementarity preserved on the horizon). This is not the awesome thing yet. The awesome thing is that compatibility of general relativity and quantum mechanics appears to require that the entanglement is equivalent to spacetime topology, to be precise, to the existence of wormholes! In fact, the modern view is that entanglement is a wormhole. (There is now even popsci jargon for this: “ER=EPR” or Einstein-Rosen equal Einstein-Rosen-Podolsky.) This unifies quantum mechanics and spacetime geometry (gravity) in a way never before imagined*, and elegantly, perhaps far more elegantly than the previous best attempt at a unification, known as String theory.
*[although, I have to say Mark Hadley, myself, and a few others had imagined something like ER=EPR way back in the mid 1990’s, but, you know, if you don’t have the skills and the academic cred, you won’t get any claim to priority, which is rough, but fair enough. Hadley did however publish a few good papers on this, and called it “QM from GR” — quantum mechanics from general relativity. He deserves some claim to priority over Lenny Susskind, truth be told. Although Susskind and co. are going in the opposite direction: “GR from QM,” which I think is the wrong direction, but time will tell. Susskind’s ideas in collaboration with Juan Maldacena are however brilliant and original, they made use of gauge/gravity duality, which Mark Hadley did not have available, and Hadley did not figure out the ER=EPR connection, though perhaps he should have!]
Yet another fascinating thing about this black hole physics is that Bob can obliterate the firewall by sending just a single thermal photon ahead to disrupt the firewall. The black hole firewalls are thus incredibly unstable. One single thermal photon is sufficient to cause a ripple in the Planck length scale firewall on the horizon plummeting all the firewall energy into the singularity, leaving Bob happy to fall across the horizon unharmed. This means there is a tug of war over information between Bob ad Alice. To extract the information from the Hawking radiation Alice has to perform such an incredibly complicated measurement, it is generally regarded by most experts that no human being would have the ability to do the experiment, it is extraordinarily complicated. One can liken it in similarity to the problem of perfectly reassembling a broken and fried up egg. You’d need to retrieve all the information in the smoke of your frying pan, and the heat that escaped from the fried egg — we are talking possible in principle, but impossible in practice. Only for the black hole physics information retrieval it would be like having the power to reconstruct perfectly billions of fried eggs, back to chicken wholeness.
Back to philosophy of mind.
All of the above conundrums about black hole information loss derive ultimately right back to Heisenberg’s uncertainty principle. We cannot make measurements without disturbing systems. Our measurements do no destroy information, but they do make certain types of information impossible to access. Information is never destroyed, but it can become inaccessible to our probes. If we make a momentum measurement on a system, we lose the ability to extract precise position information. We do however gain momentum information, and so globally information is preserved.
Although it is only a conjecture, I hypothesize something analogous (though not at all the same physics) could occur if we try to perfectly read someone’s mind so completely that we could transmit their mental qualae to someone else. We might discover that this is impossible, not grandly metaphysically, but mundanely operationally. We might thus find in the future, when neuroscience is advanced enough, that mental qualae cannot even in principle operationally be communicated. To my mind, this would be a marvellous scientific “proof” of a sort, that physicalism is not the metaphysics of our universe.
Orthodox materialist philosophers often forget this aspect of science. Science is capable of learning about It’s own limits. While it is not ever possible for science to claim all reality is physical reality (because a physical science cannot possibly definitively comment on metaphysics) it is possible that science can claim (or discover) that some things cannot be physical. This is similar to the power of “existence proofs” in mathematics. Sometimes it is impossible to construct mathematical objects, but one can prove they must exist.
In the physical sciences there are no such analytical proofs, because physics is based on empirical experiment, not axioms. But in physics we can formulate axioms and test out their consequences, and although this is an entirely different meaning to “proof” than the meaning used in pure mathematics, there are philosophical similarities. A good experiment is a lot like a “physical proof,” and can colloquially be thought of as such.
In physics we also have both certain kinds of existence and non-existence proofs (“no-go” theorems). There is physical proof that the speed of light is a universal limit. There is proof of conservation laws under given conditions. Ultimately all such physical proofs are based on experiment, which is qualitatively utterly distinct from classical mathematical proof. (Modern mathematics is slowly branching out into empiricism too, and probabilistic proof methods, thanks to computer experiments and advances in understanding of probability theory.) Nevertheless, there is similarity: both kinds of proof use certain basic logical primitives. Higher mathematics and physics alike are built on top of mathematical logics of one kind or another.
What most physicalist philosophers also seem to regularly dismiss, or ignore, is that there is no a priori (nor a posteriori, to my knowledge) reason why all truth should be encompassed within confines of mathematical logic. One has to be careful about using Gödel’s theorems to assert this sort of claim, because those theorems are technical and specialized to a narrow realm of mathematics (axiomatic mathematics) and do not apply to the general activities of flawed human socialized mathematical exploration (which admits all sorts of inconsistencies and fallacies, all of which ideally have to later be removed somehow under the straight-jacket of an axiomatic system). Regardless of Gödel’s results, the whole notion of truth transcends logic, as Alfred Tarski pointed out. (In mathematics one deals with proof, not truth. Every mathematical proof is merely a possible truth in some abstract world, but nothing more.)
The Mental Firewall
Operational non-physicalism with regard to mental qualae is a new idea to my mind that I have not encountered elsewhere before. The mental firewall conjecture is the hypothesis that any attempt to operationally extract some person’s mental quale and transmit them into some other conscious being’s mind would be operationally such a complicated procedure it would create enough energy to form a firewall, thus destroying the access to the information one is trying to transmit. To finish up this quick note, I want to re-emphasise the mental firewall conjecture involves classical processes, it does not rely upon Heisenberg uncertainty, although I think the HUP would only strengthen the case. The physics basis for this no-go theorem conjecture on ultimate mind reading, or (mind-transferral more accurately) is the physics of information complexity, not quantum theory.
What modern quantum theory has to say on the matter is however pertinent, because qubit information is exponentially greater than classical information stored in bits. The possible relevance to the mental firewall conjecture is that in order to confirm a transfer of mind, the second person has to be in some general eigenstate of more or less singular mental awareness, to report the specific qualae they’ve received. That means qubits have to decohere into classical bits, forming entanglement with the experiment/laboratory. This is how the mental firewall would form in the quantum theory. In a semi-classical description the mental qualae firewall would form due to basic entropy increase.
One Over Epsilon 