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What it is like to have been a zombie
Philosophical zombies (as opposed to the ones in the movies, which are slow-witted, bloody and broken people with a crazed and single-minded desire to eat normal people) are hypothetical creatures used in thought experiments to elucidate what we mean by the term "consciousness." They are supposed to act just like humans but lack internal experience. David Chalmers defines them thus: "A zombie is physically identical to a normal human being, but completely lacks conscious experience. Zombies look and behave like the conscious beings that we know and love, but 'all is dark inside.' There is nothing it is like to be a zombie." (

Derek Allen objects to the concept, saying it makes no sense. ( In particular he objects to the phrase "There is nothing it is like to be a zombie." I agree that the phrase "what it is like to be " is problematic, but we all know what it is trying to get at. If one has a conscious experience one can talk about it in hopes of getting one's listener to understand how it feels, how it appears or manifests itself, to the one talking about it. What is it like to eat ginger candy? Well it is a bit like eating ginger, but sweeter. It is a bit like eating sugar but far more pungent. And so forth.

The thought experiment about zombies claims that zombies have no conscious experience: nothing appears to them, they have no feeling of anything, no perception or sensation of anything. Hence, of course, they cannot describe or indicate to anyone how the world appears to them because it doesn't.

From my own first-person autobiographical experience I can provide some information that may throw light on that claim, for I have been a zombie.

My memory of having been a zombie is that I was sitting in the dentist's office about to undergo a painful procedure. A nice lady brought me a small pill and a glass of water, and I swallowed the pill and went back to reading my magazine. Then my wife was guiding me out of my car, which was parked in my garage, and into my house, where I clumsily stumbled into bed.

I have no memory whatsoever of the interval between reading the magazine after swallowing the pill and being in my garage. I'm told that I responded to instructions to get up and walk to the dentist's chair, to open my mouth and turn my head just so, and so forth. In response, I'm told, I did in fact walk to the chair, open my mouth and turn my head. After the procedure I was told to get up and sit in a wheelchair and then to get out of the wheelchair and into the car, which I did. I'm told that when I walked I rather lurched and had to be guided. My wife grabbed my belt from behind to prevent me from falling over or bumping into something. But I have no memory of any of that.

I cannot tell you how the world appeared to me when I was a zombie. As far as I know now, nothing appeared to me. But that seems implausible, because I did in fact respond to instructions, so I must have heard them. And I did in fact sit in the chair, so I must have seen it. I suppose to do a true experiment we would have to administer the drug -- Versed, a trade name for Midazolam ( -- to a willing and informed subject and then ask them to describe what they see or feel. Would someone like to take that on as a bit of experimental philosophy?

I'm not sure what this means philosophically except to note that memory seems to be an essential component of being conscious. I would appreciate your comments.

What it is like to have been a zombie
Reply to Bill Meacham
Hi Bill

I have given part of my reponse on the other thread.  Here I'll just say that you seem to be talking about a case of amnesia.  But not remembering what one did for a certain period is common enough. I gather some drunks do it quite a lot.

In any case my objection to the "zombie" thesis is that it is nonsensical - i. e. vacuous and meaningless.  So I couldn't comment on whether you were a "zombie" or not, because I sinply do not know what the proposition means.



What it is like to have been a zombie
Reply to Bill Meacham
Is memory a necessary condition of consciousness? I'm arguing not:

An inability to recall or report an experience would not rule out consciousness during it, unless you define consciousness as the integration of all experiential events.

But then events are not always immediately integrated. Witness 'flashbacks' which are an attempt to integrate lost or forgotten experiences. In fact, most emotional events are never completed in the moment but take time to integrate. So I would not argue for integration as a necessary condition of consciousness.

Also, some experiences are timeless, such as archetypal images. In fact, "memory" seems too blunt a concept to employ at times, with its reliance on a time that is somehow found in external events. Kant might object to casting internal events in the mould of an independent, transcendentally real Time.

Work by Stan Grof in the 60's using LSD showed that experiences could be recalled even when they occured under deep anaesthesia. Otherwise, lost experiences are first remembered through their emotional charge, often with physical accompaniment. Imagery may then follow. You might find this happening to you. I don't think for a moment you were blank during these events, more a slowness to retrieve.

What it is like to have been a zombie
Reply to Bill Meacham
Wikipedia says Midozolam is commonly used "for inducing sedation and amnesia before medical procedures" and less commonly for anaesthesia. I've heard of a similar clinical use of drugs before, and wondered about it. The first big question is whether you were (a) actually unconscious during the procedure, or (b) in a state of reduced, or perhaps even full consciousness, but have forgotten the experience because of the amnesic effect of the drug. Unfortunately we don't have the evidence to settle this unless someone was sitting beside your during the procedure asking the right questions.

Do you know why your dentist choose Midozolam in preference to conventional 'freezing?' In another medical case I heard about, the suggestion was that an amnesic agent was preferred to anaesthesia because the doctor wanted the patient's unimpaired subjective reports during the procedure (a painful one) as useful feedback. From the doctor's point of view, amnesia is as effective as anaesthesia in that either one effectively forestalls later patient complaints and possible lawsuits. I would love to know if these drugs really work that way, because, if they do, it would generate interesting philosophical examples. If you had to go back to the dentist, knowing that you would endure an agonizing procedure, but also that you would forget it completely and be perfectly content, should you rationally dread the experience?

You say that because you responded to instructions, you must have heard them, and since you sat in the chair, you must have seen it. But modern neuroscience has cast doubt on the simple model that says consciousness is required for what would normally be considered a conscious response. On the one hand, we have Libet's timing experiments which seem to show that consciousness is far too slow for that model to work; if presented with stimuli requiring a rapid response (e.g. hitting the brake when a pedestrian steps out in front of our car), we respond first (in about 0.2 sec.) and become conscious of it later (in about 0.5 sec.) Drugs may be capable of selectively knocking out the consciousness function, but preserving the initial response. On the other hand, we have phenomena like blindsight. Patients with damage to the visual cortex may lose the experience of seeing half of their visual field. If a researcher holds up a ruler on the patient's 'blind' side and asks how it is oriented, horizontal or vertical, the patient replies, "I don't know - I can't see it!" But if required to guess the orientation, these patients get it right with about 99% accuracy. Also, if instructed to reach out and grab the ruler, they do so smoothly and accurately, without fumbling, correctly orienting the hand so as to grasp the ruler! Blind-sight is possible because there are many visual processing centres in the brain, not all of which are, like the visual cortex, available to consciousness.

What it is like to have been a zombie
I actually went back for a second procedure and declined the midazolam. I was given a local anaesthesia and had some discomfort but no pain. And I had (I'm told) local anaesthesia the first time as well.

I take your point about consciousness not being necessary for certain responses and behaviours that seem to indicate some taking into account of the environment. I wonder if the same could be said for second-order activities such as evaluating one's performance on a task or making moral judgements about one's own behaviour. I suspect not.

I did a quick Google search on "Midazolam experiment" and found a few interesting citations.

Rats seem to like it: "... the present experiments indicate that midazolam is reinforcing in naive rats given unlimited access to the drug ...." (

It has different effects on different kinds of memory: "Performance on an implicit [memory] task (perceptual facilitation in identifying degraded pictures and words) was relatively unimpaired by midazolam, whereas performance on an explicit task (recognition memory) was severely impaired." (

I do wish someone would ask a person under the influence of midazolam to describe what they feel, think, see, hear, etc. It would be quite fascinating.

What it is like to have been a zombie
Reply to Bill Meacham
I cannot make headway with the idea that consciousness is not necessary for certain responses. Even if we note that there is a circularity hanging on "consciousness" and "response" and replace "response" with "movement" then we must be reminded that under the principles of science consciousness is neither necessary nor not (contingently) necessary for movement, but necessarily cannot affect matter at all.

As I pointed out earlier, in the 60's experiments run by Stan Grof at the Esalen Institute people could recall their experiences from operations when they were in deep anaesthesia, and not merely while they were semi-aware. Of course, it would not be productive to ask what their experiences were while under.

There is a danger of claiming too much for the brain sciences. Their anthropomorphism and animism (as arises in, for example, speaking of response rather than movement, and the idea of a consciousness function) veil the epistemological vacuum that emerges from their reductionist enterprise. Philosophers beware.

What it is like to have been a zombie
Sorry, I am having a bit of trouble with this.

First of all what does "contingently necessary" mean? Perhaps I am showing my ignorance, but the two words seem contradictory.

Second, you say "... under the principles of science consciousness... necessarily cannot affect matter at all."  What principles of science are you thinking of?

Third, I thought it might be an open question of whether and in what way conscious experience can influence matter.  Why do you say consciousness "necessarily" cannot influence matter?

I take your point about memory of what happened under anaesthesia. But in my case I was not under anaesthesia.  I was under a drug that impairs memory.  I assume that the neurological effects are different.

What it is like to have been a zombie
Reply to Bill Meacham
I suspect the conscious state under midazolam is not that different to being in a dream which is a state of consciousness which may or may not be remembered and which may or may not have at times certain motor correlates (eg moving eyes) but which is without doubt full of images and feelings and quite different to any notion of being an experience-deprived Zombie.

What it is like to have been a zombie
Reply to Bill Meacham
Yes, if I may repeat my point so I can work from it. I wrote:
under the principles of science consciousness is neither necessary nor not (contingently) necessary for movement, but necessarily cannot affect matter at all.

I was trying to be precise but generated a confusion. But my point is still well made.

There are two descriptions of necessity at work. 1) The contingent necessity that makes the rabbit be behind this tree if it is not behind that tree, and 2) the logical necessity that makes it impossible for the colour or image of the rabbit to be behind any tree. 1) has objects of the same ontological type, and 2) has objects of different ontologies. Necessity must be couched in terms of ontologies.

Consciousness is, I hope everyone will agree, not a player in a (purely physical) description of movement. This isn't because consciousness is not necessary for movement in certain (contingent) cases. Nor is it because consciousness is necessary for movement in certain (contingent) cases. Rather, it is because consciousness necessarily cannot be a player in any physical description whatsoever. 

The principle by which science claims that consciousness cannot affect matter at all is more a mission statement based on the unrestricted privilege granted to empirical, physical, objects. The idea that "mind affects matter" simply is not countenanced by science, and if in some nook or cranny we find it so countenanced, we also find no empirical evidence.

There are two causalities at work "in the head". This is because there are two ontologies (object behaviours) at work. One is physical, empirical, measurable, reciprocal - where A affects B and B affects A. The other is non-physical, not measurable, non-reciprocal  - where A affects B but B does not affect A. It is for this reason that we say that consciousness does not cause movement. We do not have the power to spark the neurons of our brain by thought alone.

With reference to the term "response": objects of consciousness (like colours, sounds, intentions) identify movement to be a response. They do not cause it to be a response. On the other hand, a physical description can only identify movement. Responses are not physically measurable, not because of any physical contingency, but because there are no physical parameters that can distinguish between a response and a movement.

What it is like to have been a zombie
Reply to Bill Meacham

On 2011-12-29, Bill Meacham wrote:

I suppose to do a true experiment we would have to administer the drug -- Versed, a trade name for Midazolam ( -- to a willing and informed subject and then ask them to describe what they see or feel. Would someone like to take that on as a bit of experimental philosophy?

Hi Bill,

I read with keen interest your experience with Midazolam, as I have been taking Midazolam orally for the past six years prior to undergoing dental procedures. I feel obliged to point out that drug dosage, age, weight (body mass), overall health, the route of administration, and sensitivity to benzodiazepines are important factors when weighing the possible effects of Midazolam on a subject. I am regularly given 7ml/14mg of Midazolam prior to dental work and am able to converse with staff, answer questions and remain self-reflectively aware (i.e., aware of my awareness) throughout the procedure. Higher doses of the drug would no doubt increase its sedating and amnesiac effects, and impair my cognitive and somatic faculties. Having said that, I can tell you a little about the altered state it produces at a dosage of 7ml. And yes, as a Midazolam user, I would call it an altered state. 

The most prominent feature of this altered state is my sense of time. For example, 5 days ago I underwent a dental procedure that entailed having my tooth prepped for a crown. The procedure lasted an hour and a half in real time, but I had no sense whatsoever of how long I had been sitting in the operatory when all was said and done. The procedure seemed to have gone rather quickly. This perceptual anomaly appears to be one of the effects of the drug on timekeeping functions [that] are governed by the basal ganglia and the right parietal cortex (Daily University Science News, 

I might add that an overall feeling of drowsiness produced by the drug blunts perceptual acuity, however much one may still be aware of what is going on and aware of being aware. Forgetfulness is another feature of Midazolam. On a few occasions I have recalled snippets of dialog I had with the dentist while I was under the influence, that did not surface to my conscious awareness until hours after the fact, when the Midazolam had worn off. Such occurrences usually produce in me a feeling of perplexity, followed by the need to fit these details back into the experience as it actually happened in real time, which simply cannot be done. 

Midazolam decreases the hyper-awareness that accompanies states of high anxiety, which is why it is a favored drug of dentists for skittish patients. There is no question that it helps to ease one into a state of relaxedness, as it depresses the central nervous system. From your description of your zombie-like experience, it appears that the dosage of Midazolam you were given did a colossal smackdown on your central nervous system. I am curious to know the dosage you were given, which should be in the chart notes of your dentist.

What it is like to have been a zombie
Reply to Bill Meacham

In my opinion, Dennett's definition of a zombie as " physically identical to a normal human being, but completely lacks conscious experience." is quit silly, and obviously absurd (i.e. falsified) for most people, as many here have pointed out.  So discussing such is a complete waste of time, and most people will justifiably not take you seriously.

Material Property Dualism predicts a different kind of zombie is possible.  To best understand what such would be like let me describe the following.  Let's imagine someone has an 'out of body experience' (or maybe a drug induced phenomenal trip) where they experience a color they've never experienced before in their life.  Let's say they call this color grue.

Even though you and I can talk very intelligently about grue, until you have experienced that color, you are a grue 'zombie'.  At least until we discover the neural correlate of such, and then can reliably reproduce the same in our brain - then we'll not longer be a grue zombie.  And clearly, the neurons that are enabling you to talk about grue intelligently, before you experience it aren't anything like the neural correlate that are responsible for true grue - so whatever it is - surely it is very physically distinquishable.

fundamental dualistic 'quale' or quality information can't be represented 'abstractly', unless you know how to property interpret it - back to the directly experienced original.  Abstracted knowledge, such as the word grue, doesn't matter what is representing it, as long as you know how to map it back to it's intended meaning.  However, absent such proper interpretation - abstracted information is zombiesh.  Given the right interpretation, it can do and behave, any way you want it to, and whatever is representing it - even if it is phenomenally like something (maybe we incorrectly think of it as being some kind of green blue until we experience the real thing), doesn't matter, again, unless you know how to properly interpret it.

OH, and I don't think you were a zombie, just because you can't remember doing the things you did under anesthesia.  I predict Quale had to be a big part of all that - even though you just don't remember such.  True zombies can remember the word grue, and talk about such, even if they haven't yet experienced true grue.  No memory is required, you just have to be able to experience grue, together with redness, greenness... and know that grue is not anything like all those qualities.

Brent Allsop