trepanningThis piece in the Atlantic raises a question we have touched on before: anaesthesia. How do we know it works, how do we distinguish it from amnesia, and how much does it matter? What is supposed to happen is that when we get an anaesthetic injection, or gas, we simply stop feeling pain; possibly we stop feeling anything. It is certainly more complicated than that: the drugs used by doctors may simply stop us feeling pain – we more or less know with a local anaesthetic that that’s sort of what happens – but they may also, or alternatively, stop us remembering, or caring about, the pain; they may also merely stop us moving or complaining. Some of the drugs used by anaesthetists apparently do only one of the three latter things, with no direct influence on the pain experience itself.

This matters most obviously when things go wrong, and in the middle of a surgical operation a patient resumes consciousness while remaining paralysed, experiencing all the terrible pain of being cut open without being able to give any sign of it. Because of the memory-erasing effects of some of the drugs used we cannot be sure how often this happens, but it is accepted that sometimes it does.

This is one of those areas where the apparently airy-fairy disputes of philosophy suddenly get real.  A number of people are sceptical in principle about the reality of the self, of consciousness, and of subjective experience: but I think you need to be quite bold to stick to scepticism when it involves dismissing pain on the operating table as a mere conceptual confusion, something we need not be too concerned about.

There is, however, little agreement about some fundamental issues. Does it matter if I feel terrible pain, but then forget about it completely? I’d say yes, but a friend of mine takes the opposite view: if he doesn’t remember it he considers that as good as not having had the experience in the first place. Of course I would have minded at the time, he says, but that’s not what we’re talking about; we’re talking about whether I should mind now. Ex hypothesi, if I’ve forgotten, my mind is in exactly the same state as if I never had the pain, and it’s incoherent to say I should worry about a non-existent difference.

I have to concede that my point of view opens up many more problems. Since memory is fallible, there might be lots of forgotten pains I should be worried about; but if I have a false memory of a pain that never happened, is that also a cause for concern? It’s possible to be in a state of mind in which one feels a pain but somehow does not mind it: but what if I start minding about it later? What if I forget that I didn’t mind? What if I did mind but the pain was actually illusory? What if I felt the pain unconsciously? And what if the memory then became conscious later? Or what if I felt it consciously but have only an unconscious memory? Do animals feel pain in the same way as we do? Do plants? If a drug dials my level of consciousness back to monkey level, dog level, chicken level, lizard level, ant level – does pain still matter? If I feel pain while operating on a protozoan mental level, does it matter more when I remember it on a fully human level? Do imaginative people suffer more (as, apparently, red-headed people tend to do)?

This may all sound stupidly speculative, but the questions are genuine and we’re talking about whether I’m in agony or not. It would be great if we could bring all this out of philosophy zone and into science, but there are problems there too. The Atlantic article recounts difficulties with the BIS monitor, supposed to provide a simple numerical reading for the level of consciousness based on electroencephalograph readings. Perhaps it’s not suprising that the BIS has been questioned: an electroencephalograph is hardly cutting edge brain technology. A more fundamental problem is that it has no known theoretical basis: the algorithm is secret and the procedure is based entirely on empirical evidence with no underlying theory of conscious experience. Providing sound empirical evidence of subjective experience is obviously fraught with complications.

Step forward our old friend Giulio Tononi, whose theory of Phi, the measure of integrated information and hence, perhaps, of consciousness, is ideally suited to fill the conceptual gap. With Phi in one hand and modern scanning technology in the other, surely we can crack this one? I don’t know whether the Phi theory is really up to the job: if it’s true it might tell me why consciousness occurs in the brain and how much of it is going on, but it doesn’t seem to explicate the actual nature of the pain experience, and that leaves us vulnerable because we’re still reliant on the fallible reports and memories of the patients to establish our correlations. Could we ever be in a position where the patient complains of terrible pain and the doctor with the Tononi monitor tells them that actually he can prove they’re not feeling any such thing?

Perhaps we can imagine a world where the doctor goes further. Great news, he says, we’ve established that you’re a philosophical zombie: although you talk and behave as if you have feelings, you’ve actually never felt real pain at all! So no injection for you – we’ll just strap you down and get on with it…


  1. 1. Roy Niles says:

    This reminds me of a theory where military interrogators argue that it’s OK to severely torture prisoners if you plan to kill them anyway. That theory being that once they’re dead they won’t remember the pain. And I suppose you could extend that thought to concluding that since we’re all destined at some time to die, we might as well stop worrying about causing any painful thing, since none of us in the end will remember it at all.
    On the other hand we live for the moments where we find our purposes in the need to feel good, other’s purposes found in hurting us not withstanding.

  2. 2. Kevin Kim says:

    Is there a such thing as “illusory pain”? Dr. William Vallicella argues forcefully that “a pain’s esse IS its percipi.” I’m inclined to agree: if you think you’re experiencing pain, then you’re experiencing pain. The source of the pain might be illusory, but the pain itself cannot but be real.

  3. 3. Peter says:

    Kevin – yes, I think most people would agree that while you can wrongly believe that you see a chair you can’t wrongly believe that you feel a pain, this being a rare example of infallibility to stack up alongside Descartes cogito (if you accept the cogito). I would have said so myself until last year.

    But Eric Schwitzgebel has argued that there’s more scope for error than we think, and I found his account generally pretty convincing.

  4. 4. Eric Thomson says:

    I have thought I felt a pain in my stomach, but it turned out to be hunger.

  5. 5. Vicente says:


    you can wrongly believe that you see a chair

    I believe not, wouldn’t it be: you can wrongly believe that there is a chair because you see a chair, or you incorrectly labeled the mental image you saw as a chair. But the image you experienced was that, whatever it was.

    You could wrongly believe that there is something wrong with you because you feel pain, true, or you could feel pain induced by psychological suggestion and wrongly believe there is some physical damage or many things… and there is placebo and nocebo….etc…

    There is no doubt that “senses are unreliable”. This is a different issue.

    But the direct phenomenal INNER experience, we are having at a precise instant, is what it is, irrespective of its relation with “reality” or its origin.

    Now, how do we name a particular experience, e.g. stomach hunger driven upset? stomach pain? that is a different issue.

    In Schwitzgebel’s examples like: “my wife can rate my emotional state better than myself” there is a trick, he breaks the instantaneous nature of the experience, he has to make a time and personal detachment from the experience, to make partial approach to it, and with some latency.

    The global experience is what it is, infallible. The experience assessment can be many things, and of course there is scope for error in it.

    I don’t see why you find Schwitzgebel’s approach so compelling.

  6. 6. Arnold Trehub says:

    Vicente: “The global experience is what it is, infallible. The experience assessment can be many things, and of course there is scope for error in it.”

    I agree with Vicente.

    If there is phenomenal pain during an abdominal operation under general anesthesia, there must be an interoceptive sensory response to the stimulation of a pain receptor. It seems to me that this would necessarily result in bursts of afferent discharge that we should be able to monitor electrophysiologically. Also, if this were the case, I don’t see how it would be detected by Tononi’s qualiascope.

  7. 7. Arnold Trehub says:

    Addendum to my above comment:

    If bursts of neuronal activity in pain regions were temporally correlated with changes in skin conductance and electro-ocular rem activity, this would be good evidence that the pain was consciously experienced under anesthesia.


    Storm, H. Changes in skin conductance as a tool to monitor nociceptive stimulation and pain. *Curr Opin Anesthesiology (2008): 796-804.

    Mashour, G. A. Dreaming during anesthesia and sedation. *Anesthesia Analgesia * (2011): 1008-1010.

  8. 8. Eric Thomson says:

    Experiencing X and judging (or believing) that one has experienced X are different. The latter is clearly fallible, and that is the relevant point (Anton-Babinsky syndrome (blindness denial) may be a striking example (though interpreting this is actually tricky), but I know from personal experience that judgments about experiences are fallible).

    I’m not sure it even makes sense to say that experiencing X is fallible, or infallible. That seems a category mistake, like saying a stone is fallible or infallible. A stone is not fallible, but that doesn’t imply it is infallible. To be in that semantic ballpark is to be a propositionally structured representation, and it isn’t clear at all (indeed, it seems likely false) that experiences are propositionally structured representations.

  9. 9. Eric Thomson says:

    OTOH a picture could be said to be fallible or infallible, and that isn’t propositionally structured. But we aren’t talking about how well an experience depicts the world, but our judgments about the experience itself. So we come back to my first paragraph in the previous.

  10. 10. Jorge says:

    Peter, it seems you and I play similar mind games with our colleagues. I too had a similar discussion with one of my coworkers, where I proposed the following deal:

    Dr. Evil will strap you to a chair, and torture you relentlessly for 3 days, then give you a drug that will eliminate all memory of the experience, permanently. He will pay you $50,000 if you volunteer. Do you take the money?

    He said he would, while I would never take this deal. Nonetheless, I had a very difficult time explaining exactly why it was a bad deal. The best way to get someone to ‘intuit’ my perspective was to use a surrogate: give them $50,000 if a loved one gets strapped to the torture chair and then has their memory erased. All of a sudden, the moral issue is sharpened.

  11. 11. Roy Niles says:

    The moral issue was sharpened? Come on, it just became a different moral issue. Deciding to let someone treat you immorally is quite different from deciding to have someone else immorally treated. It’s a false dilemma. You gave permission for immoral acts, and your loved one not only didn’t but had no choice.

  12. 12. Jorge says:


    The idea was that the individual justification for taking $50,000 is that the memory-erasing treatment somehow makes the pain “not real” or “not matter”. While you are correct in saying that making the choice for someone else adds a complication, it was still interesting to see how quickly the flaw in the original individual reasoning was revealed by asking for a surrogate. If the pain “isn’t real” or “doesn’t matter” after memory deletion, why should you care WHO goes into the torture chair?

  13. 13. Roy Niles says:

    But the memory erasing treatment can’t erase that fact that you did feel a torture that your tissues will have been effected by even if your memory isn’t. (I won’t ague that this is a silly thought experiment in any case since memory erasure can’t be presently counted on to happen.)
    More importantly, anyone who can empathetically feel the prospective pain of a loved one needing to occur will instinctively want them to avoid the occasion, regardless of whether the feeling can be later turned somehow to an unfeeling.
    So yes, we should care if anyone goes to the torture chair, and especially someone close to us, because we have to care. In theory, we accept that they might forget the pain, but we know we won’t forget our empathetic memory of it.
    And further you can’t realistically take the chance out of the experiment that the torture itself would kill the friend or relative. Would we see that as acceptable pain erasure also?
    And I repeat that it’s in the end a false dilemma. In either case the prospective pain would matter.

  14. 14. Jorge says:

    Roy, you do understand that thought experiments in philosophy tend to ignore a lot of technical and pragmatic issues for the sake of making a point right?

    You posted:
    “the memory erasing treatment can’t erase that fact that you did feel a torture ”

    That’s the issue under discussion. In the original post Peter wrote it as “…a friend of mine takes the opposite view: if he doesn’t remember it he considers that as good as not having had the experience in the first place…”

    I would tend to agree with you, which is why the way I try to persuade people who agree with Peter’s friends is by using a surrogate: pain is real even if the memory is erased, which is why you wouldn’t want to see a loved one tortured (and memory erased) in this way.

    The issue is far from settled.

  15. 15. Roy Niles says:

    Yes, I do understand that thought experiments in philosophy tend to ignore a lot of technical and pragmatic issues for the sake of making a point. That’s why a number of these experiments are silly. But I still addressed the point it was attempting to make, right?
    A point which you didn’t quite get if you’ve simply concluded that the “pain is real” even if the memory is erased. I think the question was something like, is the pain still real, etc.

  16. 16. Richard Bennett says:

    Is it possible that the “mode of experience” for a philosopher such as yourself is substantially different than the average persons?
    By that I mean to ask whether “thinking about thinking” is itself such a fundamental factor in what is being experienced that the thinking itself can change the experience from one of immediacy to something that is better characterized by what we commonly call thought, rather than pain.
    I guess what I’m trying to say is that experience is just experience, but thought about that experience is a much more worthwhile and interesting pursuit.

  17. 17. Peter says:

    Richard –

    It seems possible. It certainly seems to be the case that thinking about a sensation affects the experience, so that arguably we can never really know for sure what an unintrospected experience is like.

    It is said that one way of dealing with pain is to think about it; by concentrating on the details of the experience and trying to get them clear we can apparently stop the pain actually hurting. Dennett, I think, tested this theory on a visit to the dentist and found that although thinking about the detailed phenomenology of the pain did in some sense detach him from the pain, he found it such an effort to keep up that after a few minutes he chose to suffer the pain instead!

  18. 18. Callan S. says:

    I guess the philosophical zombie part is a joke. But I’ll bite anyway!

    I don’t get why these examples are one sided?

    “Good news, you’re a philosophical zombie, so you never felt real pain! So we’ll get started”

    “Wait, doesn’t that make you a philosophical zombie as well?”

    “Hmmm, oh yeah, I forgot!”

    “So…do you like the not real pain of knives going into you?”

    “Hmmm…you know what, I don’t like that not real pain! That not real pain is quite painful!”

    “So I might skip on the not real pain then?”

    “Oh! I see, we do have something in common, just as before the idea of philosophical zombies we had something in common – it’s just now we have a different understanding of the same thing we have in common! But actually I’m evil and the whole philosophical zombie was just a ruse…”


  19. 19. Niko says:

    This may be a little late but I would still like to add my two cents.

    In this whole discussion about pain there hasn’t been much discussion about what pain is. And I haven’t seen anything about detecting it in patients beyond brain scans or from their memories either.

    Both seem very relevant and can imo get us a lot closer to an answer than speculative thought experiments. Physically speaking pain is a result of electrical signals arriving at the brain and being processed there. We don’t necessarily need to know what exactly happens at the line joining consciousness and brain, we can learn a lot just looking at the physical part of the process.

    It stands to reason that the electrical signal or the brain process could be disrupted in such a way as to not feel pain. In fact it seems like the best explanation for the effect of local anesthetics and pain killers.
    Therefore it is a reasonable assumption that if such drugs are given together with drugs that put the patient to sleep or lose consciousness some other way, they will not experience pain.

    Furthermore, to see whether someone is experiencing pain, we don’t need to look at brain scans either. Because the sensation of pain is part or the result of a process in the brain, we can look for other phenomena that are associated with the process. Such as increased heart rate, muscle tension or change in breathing.
    So even for anesthetics that are bound to knock out the patient, it is a reasonable to assume that no pain is experienced, even if they should somehow regain consciousness.
    The physical process associated with pain has a number of other effects associated with it as well, if none of these occur then why should the sensation of pain?

    PS: I realize anesthetics might not always be 100% effective, so don’t take my use of the phrase “no pain” to literal, it could also be heavily reduced pain.

  20. 20. Arnold Trehub says:

    Niko, see comment #7 above and the two papers referenced.

  21. 21. PhiGuy110 says:

    BTW, Tononi’s chapter on pain in his book Phi is a bone-chilling must-read. It features a “torture artist” called “The Master” who uses a brain-machine interface to torture his prisoners and discover the “perfect pain.” But, he gives them an elixir so that they don’t remember any of it (as is being discussed in the post). It’s a strange idea; as Tononi writes in the book, “What kind of world is this?”

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