May 17 2012

What Is Consciousness? Another Reply to Kastrup

I hadn’t planned for this topic to take over my blog this week, but it happens. Judging by the comments there is significant interest in the issue of consciousness, and Kastrup and I are just getting to the real nub of the argument. So here is another installment – a reply to Kastrup’s latest offering. First, however, some background.

Materialism, Dualism, and Idealism

Philosophers of mind, such as David Chalmers, now recognize three general approaches to the question – what is consciousness? Materialism is the view that the mind is what the brain does. This is often stated as the mind is caused by the brain. Some commenters took exception to this phrase, saying it implies a dualist position, that the mind is its own thing,  but I disagree. The brain is the physical substance, while the mind or consciousness is a process that emerges from the brain. A dead or deeply comatose brain has no mind, so they are manifestly not the same thing. Language here is a bit imprecise, but I think the phrase – the brain causes the mind – is an acceptable short hand for the materialist position.

Dualism is the position that consciousness is something separate from the brain and not entirely caused by it. It may be a separate property of the universe (property dualism) or be something beyond the confines of our material universe. Whatever it is, it does not reduce to the firing of neurons in the brain, which cannot, in the opinion of dualists, explain subjective experience.

The third position, the one that Kastrup holds, is idealism – the claim that consciousness is all there is and the physical universe, including the brain, is a manifestation of consciousness. Kastrup uses the metaphor of a river, where the flowing water is consciousness. The material world is like a whirlpool in the stream – the whirlpool has a definite existence in time and space, you can point to it and say, “there it is,” but it is comprised entirely of the stuff of consciousness.

I am an unapologetic materialist. I think the mind is entirely explainable as a manifestation of the brain’s biological function. The brain is thinking and feeling meat. I am not emotionally invested or tied to this conclusion. It would be quite cool if we were  living in a computer simulation or there was some other deeper layer to reality that would allow my consciousness to survive the death of my brain. I have simply found no compelling evidence for such a conclusion. Show me compelling evidence and a logical argument and I’ll buy it – but I’m still waiting.

This does not mean, of course, that I can explain exactly how the brain generates the subjective experience of consciousness. It is important to separate the question of how the brain causes consciousness from if the brain causes consciousness. The evidence for the brain as the sole cause of the mind is, in my opinion, overwhelming. The how is a bit more tricky. I personally am on the fence between two materialist positions. One position is that the “hard problem” of consciousness, as Chalmers calls it, is really a non-problem – it is simply made of all the easy problems of neuroscience. We are making good progress in figuring out the neural correlates to the different aspects of conscious experience – motor planning, executing motor functions, primary and secondary sensory processing, visual processing, etc. The more abstract functions are more challenging, but we are making steady progress. It’s possible that once we solve all these individual questions there will be nothing left – in other words, our subjective experience will be made up of all the subsets of consciousness without the need for there to be any other process that is itself consciousness. In this view consciousness is simply the real time processing of sensory input and internal communication and monitoring.

It is also possible that there is some other function within the brain that is essential to consciousness that we have not yet identified. There are theories about the “global workspace” – a distributed network in the brain that is like the central command center. Right now I think this is an open question, and I know neuroscientists of either view. Either way, it’s all still brain function.

Another compelling reason to accept the materialist paradigm of neuroscience is that it has been and continues to be extremely successful. In science theories are judged not only by how well they fit the data, but by how useful they are as predictive models – and the materialist position that brain function is the mind has been fantastically successful.

There does not appear to be any intrinsic limit to our ability to map and alter anything considered to be part of our subjective experience. Damage or alteration to the brain can change your sexual identity, your moral decision making, your personality, your ability to even think about the world. Patients with non-dominant hemisphere strokes, for example, often have what is called neglect – they do not know that the left half of the world even exists. There is no model inside their brain for the left half of their body or the world, so they cannot even think about it.

Non-materialists often dismiss this as mere correlation, but that is not fair, in my opinion. The correlation is incredible, and predictive. To give just one more example, synaesthesia is the phenomenon of different sensory modalities mixing together, so synaesthetes will smell color or perhaps perceive numbers as having a physical texture. There is evidence for more robust neural connections and activity between the relevant brain areas in synaesthetes. That is a pretty compelling neural correlate.

Further still, the arrow of temporal correlation, which should go from cause to effect, seems to go from brain activity to subjective experience. Studies so far show brain firing happening prior to awareness of the subjective state.

Yet another reason I currently accept the materialist paradigm is that there is no independent evidence for anything else – for a consciousness separate the brain. There is no evidence as to what consciousness would then be, and how it interacts with the brain. Dualism and idealism are just inventing a massive mystery to explain what they perceive as another mystery, and they don’t really accomplish anything. In this way non-materialist notions of consciousness are very much “god of the gaps” arguments. They are identical, in my opinion, to vitalism – the notion that there is a life force. Non-materialists start with the sense, the gut feeling, that consciousness is something different than physical matter. If you read the comments to Katrup’s articles or my previous entries on this topic, or if you read dualist articles you will read this over and over – subjective experience is not material. They then proceed from that premise. This, however, is just a failure of language or imagination, not the materialist paradigm. They then essentially invent a mysterious magical consciousness that does not need to obey the laws of physics to explain consciousness. They also, therefore, are confusing unexplained with unexplainable (with regard to consciousness).

Vitalists, likewise, felt that living things had to be fundamentally different than non-living things. Life could not just be what you get when you add together all the little things that biology does. There had to be something more, some life energy which is its own thing. They then used the vital force to explain any process not currently explained by biology. Over the centuries, however, biology was eventually able to tackle all the basic functions of life. Eventually there was simply nothing left for the vital force to do. It was not so much proven wrong and rendered unnecessary – not even wrong. I believe that dualism/idealism is in the midst of suffering a similar fate.

Kastrup’s Latest Reply

With that as background, let’s go on to Kastrup’s latest reply. I will ignore any tedious further discussion about form or tone, and simply address the key points that he is trying to make.

He writes (italics are my prior writing that he is quoting):

“The problem, from a scientific point of view, is that the notion that the brain modulates consciousness becomes operationally inseparable from the notion that the brain causes consciousness, at least in terms of the experimental relationship between brain function and mental function.”

This is clearly untrue. The modulation hypothesis predicts that there are subjective mind states that do not correlate with objective brain states. Such prediction is invalid under the causation hypothesis.

I guess I was unclear in my statement above. I added the caveat, “at least in terms of the experimental relationship between brain function and mental function,” specifically to account for claims of consciousness separate from brain function, but I can see that this was not sufficient. My point was that the brain as modulator hypothesis is a convenient way of explaining away all the neural correlates to consciousness, but adds nothing in terms of predictive ability or even as an explanatory model. What Kastrup is saying is that the brain as filter theory predicts imperfect correlation, but I don’t see why this would be true.

What this formulation does do is set up a situation in which any anomaly in our data (imperfect correlation) can be interpreted as evidence for the modulation hypothesis. This is a very weak “prediction” – that there will be anomalies in the data. Of course there will be. The brain is horrifically complex, and our current tools for imaging brain function are relatively crude. This is really just another version of Egnor’s argument that imperfect correlation is evidence of dualism – it isn’t – it just reflects the limits of current technolgy and neural models.

In other words – the modulation hypothesis is unnecessary. It adds nothing to the materialist paradigm in terms of explaining or predicting how brain function will correlate to subjective experience. It adds an additional element of consciousness separate from brain function – a massive new assumption that is not justified. The best the non-materialists have is anomaly hunting – looking at current research and then focusing on studies that show imperfect correlation or some aspect of brain function that is difficult to explain with our current models. They are exploiting the leading edge of research where data is preliminary and uncertain and using it as if it were a solid and verified premise.

Further, I don’t buy the modulation hypothesis explanation for the correlates we do see, including the temporal relationship of brain activation preceding awareness. How, for example, does modulation explain synaesthesia? You have to contrive a notion of modulation, again, that completely replicates the findings of strict materialism.

Kastrup continues:

“There doesn’t seem to be anything coming from outside the brain – but worse, the concept is completely unnecessary. It is sliced away cleanly by Occam’s razor.”

This is acceptable only if one ignores the wealth of evidence for the existence of mind states uncorrelated to brain states. Novella seems to dismiss all evidence related to, for instance, Near-Death Experiences (NDEs),

This, of course, is the real crux of the matter – is there evidence for consciousness separate from brain function? I maintain that there is not. NDEs are a good example. The evidence for NDEs is mostly anecdotal. Whenever a controlled look is taken at NDEs there is no evidence that consciousness is occurring while, for example, the brain is not functioning. What we have at best are memories reported after the fact – after a long period of recovery (you don’t just wake up from a cardiac arrest). During the recovery period they may form memories that are dream-like and they may interpret them as occurring during the cardiac arrest, even though they formed later. Also, during many NDE situations brain activity is not entirely lost, there are bursts of activity in different parts of the brain. Further NDE-like experiences (there is a range of experiences that are referred to as NDE) can be triggered by certain drugs, like ketamine. All of the components of NDEs can be generated by brain activity.

Kastrup and I both agree that we don’t have space in this current debate for a full treatment of the NDE issue. My point, however, is simple – NDEs can be explained as brain experiences. At the very least we have to admit that the issue of NDEs is highly controversial. This is not like plate tectonics or genetics – it is not reasonable to use NDEs as if they were an accepted or solid scientific premise. They are not. In my opinion, the interpretation of NDEs as non-material is an unnecessary and fringe interpretation. Kastrup, however, wants to use it as an established premise. This is unreasonable.

About this he further writes:

My point is this: Though Novella is entitled to hold any opinion he wishes regarding the evidence available for uncorrelated mind states, the evidence is substantial enough (in the form e.g. of myriad peer-reviewed scientific publications, like van Lommel’s article in The Lancet, to mention only one example) that reference to it in any debate about the  mind-body problem is legitimate; it’s a legitimate point of contention. To claim otherwise is to dismiss the validity of the peer-review process, which, for obvious consistency reasons, would force Novella to equally dismiss the other scientific results he uses to justify his positions. So I do not grant Novella’s claim above, which I consider arbitrary and incorrect.

I completely disagree. First, peer-review is not sufficient to establish scientific legitimacy. Much of what finds its way into the peer-reviewed literature is crap, and much of it may be good science but turns out to be wrong. What is more important than just passing the peer-review bar is what happens next – when the scientific community assesses the science. It is premature to cite NDEs as evidence for anything. They are, at best, an anomaly yet to be explained, although I think they have been adequately explained. Kastrup is simply wrong about the role of peer-review – it is not sufficient to establish legitimacy. NDEs are not a valid premise for his position – they do reveal the weakness of his position.

As as an example of my point, there are many peer-reviewed publications, even in respected journals, that deal with topics generally rejected by the scientific community.  Homeopathy is a great example. It is demonstrably absurd and wrong, and yet proponents can make the same lame legitimacy argument by citing publications in respected peer-reviewed journals and the occasional scientist who supports it. None of this adds up to homeopathy being legitimate, and I would not accept it as a premise to pronounce the demise of materialism.

The Psilocybin Study

Kastrup continues to make much about a recent study of the effects of psilocybin on the brain. This is another example of him exploiting new and controversial research as if it establishes a solid premise, and he continues to misinterpret the study. For the record, despite his complaints I have read all of the articles he linked to on this topic, I just did not find any of it cogent or compelling. But let me address his specific points in detail.

For background, psilocybin is a psychedelic drug that causes surreal hallucinations. Previous studies have found that the drug increases activity in certain parts of the brain. The new study that has Kastrup so excited found that psilocybin decreases activity in certain parts of the brain, and found no increase. Kastrup maintains this study (if confirmed) disproves the materialist paradigm because it breaks correlation between brain states and mental states. His arguments, however, are hopelessly superficial and naive of modern neuroscience – and I am not the first neuroscientist to point this out.

Here is Kastrup’s full discussion of the issue. He argues that decreased brain activity cannot explain the intense experiences associated with psilocybin use within the materialist paradigm. His arguments all seem to hinge on a false assumption (although he tries to deny this) –  that the intensity of the subjective experience relates to the raw neuronal activity in the brain (the proportionality argument).

First I need to emphasize that this one study, an fMRI study, is insufficient to establish that there is no increase in any type of brain activity anywhere. This type of imaging infers brain activity by looking at a subset of metabolic processes. PET scanning looks at brain activity through different metabolic processes. Prior PET studies did show increases in brain activity with psilocybin. From the existing evidence we might conclude that some processes increase while others decrease – or we have to say that we have confilicting evidence and therefore we don’t currently know what the answer is. Again – hardly appropriate to take as a premise for changing science as we know it.

But let us assume that the new study is correct and psilocybin only decreases brain activity. The neuroscientific interpretation of this is that it is reducing the modulation by one part of the brain on other parts of the brain. This is changing net subjective experience. Since processing that is involved with higher order reality testing is inhibited, it’s no suprise that reality-bending experiences result. These experiences are only “intense” because they are so unreal. This does not require increased neuronal firing. In fact, reality testing and the higher cognitive functions are much more demanding than the more primitive processing that happens in the evolutionarily older parts of the brain. When the processing-intensive frontal lobes are reduced or removed from the equation, an overall lower amount of brain activity could result in wierd psychedelic and emotionally “intense” experiences. This in no way breaks the materialist predictions of correlation.

Kastrup argues that if the above explanation were true, then we would expect one of three things: First, we may see increased activity in the disinhibited areas of the brain. This is not necessarily the case, however. The activity might be the same, but since it is no longer being modulated and modified by reality testing centers the net experience can be very different.

Also – to clarify a point I made in my previous reply to Kastrup – I was not arguing that proportionality never exists when looking at brain function. My point was that proportionality does not necessarily exist in every case, and so the absense of proportionality does not break materialist correlation. There certainly is increased brain activity correlating with increased subjective mental activity, but this simple magnitude correlation does not hold when we are talking about the interaction among the various brain regions.

Kastrup further argues that if the brain regions responsible for the psychedelic experiences are not increasing their activity, then they must have been active all along, but, he argues, this makes no sense. Why would such hallucinations being going on in our subconscious all the time? He writes:

Therefore, the second scenario implies that unfathomable ‘sci-fi’ fantasies are subconsciously playing themselves out in our brains on a regular, on-going basis. What evolutionary advantage could this possibly have?

Not necessarily, but also it is not unreasonable that, in essence, fantasies are going on in the background all the time. Our brains are pattern recognition machines, and there is a vibrant internal conversation going on within our brains all the time. We are aware of only a small amount of what goes on in our brains. So if one tiny part of this comes into our awareness because it is no longer be crowded out by processing-heavy reality testing, that makes perfect sense. Further, the elements that make up those fantasies could be active all the time but don’t manifest as narratives because they are filtered by reality testing modules. Once disinhibited, however, they contribute to our conscious narrative.

This relates somewhat to Kastrup’s third point of rejection – he rejects the notion that activity in the fantasy-generating parts of the brain are active but not coalescing into coherent activity, but then once disinhibited they do. This is a bit of a straw man, based upon a simplistic understanding of brain function. He writes:

Even if we leave aside the fact that postulating such an unknown mechanism is quite contrived, this third scenario still implies that the brain activation signatures of unfathomable and mind-boggling psychedelic ‘trips’ are indistinguishable from ordinary, subconscious ‘noise.’ How reasonable a hypothesis is this, in light of the paradigmatic assumption that experience is brain activity?

I think Kastrup vastly underestimates the subconscious “noise” that is going on in the brain during normal activity.  There is a large amount of both psychological and neuroscientific evidence for the conclusion that there is a great deal of subconscious processing, including generating lots of noise. We attend demonstrably to a very small portion of this activity. Our brains select small portions of both sensory input and our internal communication to weave into a highly constructed narrative we experience as our stream of consciousness. Altering this stream significantly without changing overall brain activity makes perfect sense.

Kastrup has simply demonstrated his own naivete regarding the complex brain interactions that make up our conscious experience. His arguments all hopelessly fail for this reason. He is using preliminary and contradictory evidence as a premise, combined with false assumptions about proportionality and the meaning of things such as ‘intensity’ of experience, and then combining it with demonstrably wrong gut feelings about what is reasonable to assume about brain function.


Kastrup ends with this:

“He should at least exhibit a little tiny bit of humility when confronting neuroscientists about neuroscience”

Truths and arguments stand on their own or fail on their own. Either way, they are not determined by authority, otherwise we would still be living under the notion that the Earth is the center of the universe.

Kastrup did not give my complete quote, I actually wrote:

He should at least exhibit a little tiny bit of humility when confronting neuroscientists about neuroscience (which he does also here  – apparently I am not the first neuroscientist to call his understanding of neuroscience “naive”). This doesn’t mean we’re right and he’s wrong, but it should at least give him pause. I know I get very concerned about my own understanding of a topic if experts in the field contradict me.

I specifically added the caveat because I knew that Kastrup would reply exactly as he did, but apparently that was not enough to dissuade him. The cheap shot was just too tempting, so he ignored what I wrote and did not include it in his quotation.

It is also interesting that he is now arguing that authority is not a reliable guide to correctness, while above he was enthusiastiacally citing peer-review and prestious journals as a source of scientific legitimacy.

I, of course, agree with his conclusion. Arguments stand or fall on their own. I think I have demonstrated that Kastrup’s arguments fail at many levels. He relies upon preliminary or controversial claims as solid premises. He misunderstands the current synthesis of our neuroscientific understanding of how the brain works and how brain functioning relates to consciousness.

Our experience of reality is demonstrably constructed by the brain. When you alter the underlying brain function, you alter that construction. People can be made to feel as if they do not control their own limbs, or that they have extra limbs, or that sound has a color, that parts of the world do not exist, that their spouse has been replaced by an imposter, or that they are one with the universe. We can do all this by poking around in the brain.

Psychological manipulations can make you miss “obvious’ events occuring right in front of you. Optical illusions are dramatic misperceptions of reality that can not only be correlated with brain activity they can be convincingly explained by specific information processing that happens in identifiable locations within the brain.

The obvious conclusion from all of this is unavoidable – our brains actively construct our subjective experiences.


Kastrup has written a reply. I am not sure it is worth another reply by me – I will decide later. He really only makes one point, represented here:

The fallacy here is that Novella talks merely of ‘intensity,’ while conveniently ignoring the other hallmarks of psychedelic experiences: Their structurecoherenceunfathomable complexity, and the fact that they are often described as “more real than real.” (see Rick Strassman’s study at the University of New Mexico’s School of Medicine, described in his book The Spirit Molecule). Novella is creating a straw-man by subtly, yet massively, under-characterizing the experience, and then casually explaining such under-characterization away.

He describes the psychedelic experience over and over again as a “peak” experience. This is just more neuroscience naivete on his part. He gives no operational definition of what “peak” means (seems like just another way of saying “intense”). He doesn’t address my points – I think he didn’t really get them.

Psychedelic experiences are so emotionally mindblowing because they are outside of our everyday neurological experiences. They can be life changing in part because they challenge our concept of reality They reveal how constucted our reality is by deconstructing it. It may seem “realer than real” because reality testing is not functioning, telling your brain that something is not real. None of this  implies that there has to be more neuronal firing going on.

Kastrup also acknowledges my point that there is a lot of background noise in normal wakeful consciousness, but then seems to think this supports his position. He just doesn’t seem to get it.

There is nothing “peak” about psychedelic experiences. They are just really different from what we are used to, because our brains are functioning differently. Some processing-intensive modules are out of the mix, like reality testing. So reality is constructed differently from anything we experience in normal wakefulness. Of course these are intense and life altering.

The bottom line is that Kastrup is making a god of the gaps argument. He can’t make sense of the psilocybin research, so he is using it to support his metaphysics. His declaration that materialism is dead is premature.

Like this post? Share it!

187 responses so far