Near-Death Experiences on TV

Why quantum coherence cannot explain the NDE

Sceptic Magazine 17(1), Spring 2004, pp. 8-10

On 5 February 2003 I appeared in a BBC documentary “The Day I Died”. Afterwards, Chris French, of the UK Sceptics, asked me to write an article about it for the Sceptic magazine to explain the quantum theory of consciousness so enthusiastically presented there.  In fact this programme had upset me very much for its biased and dishonest reporting, so I was glad to have the chance to write about it.

I never should have said yes. I’d promised myself I wouldn’t do any more “renta-sceptic” slots, and here I was appearing on one of the worst ever TV shows on NDEs. So how did it happen?

The producer, Kate Broome, told me that “The Day I Died” would take the science seriously, that there would be a searching exploration of the whole topic of consciousness, and that this programme would be entirely different from its predecessors. So I believed her. She and her BBC team came to my house and we did a very interesting and enjoyable interview. We covered not only the physiology of NDEs, but theories of consciousness, the reasons why quantum theories of consciousness fail, the nature of self and why NDEs might be genuinely mystical experiences without being evidence for life after death.

Then I saw the advance advertising: “NDEs used to be the domain of parapsychology, but now research by some scientists and medics is daring to suggest the impossible – that NDEs are evidence that the mind can live on after the brain has stopped functioning…”. Different from its predecessors? Hardly. Popular? Of course. This is what every previous NDE programme has claimed, and this is what most people already believe.

In the end, as anyone who watched the programme will know, “The Day I Died” was just an updated version of all the myriad shows that have gone before.  Some of the new cases were excellent, and the interviews with NDErs were fascinating, but the science was not. Peter Fenwick and Sam Parnia described their recent research and their belief that it proves the independence of mind. Renta-sceptic said her usual pieces about tunnels, lights and how they are constructed in the dying brain (they could have cut them from interviews I did ten years ago instead of carefully extricating them from what I wanted to say this time).

Finally they got to consciousness. With clever computer graphics and Horizonesque hype they explained that brave scientists, going against the reductionist grain, can now explain the power of the mind to transcend death. It all comes down to quantum coherence in the microtubules. And to make sure the viewer knows that this is “real science” the ponderous voice-over declared “Their theory is based on a well established field of science; the laws of general relativity, as discovered by Einstein.”

This was where my fury erupted. As I wrote to the producer afterwards “it is dishonest to present a completely unworkable and mysterious theory as though it were real science, and to dress it up in the trappings of real science, as you did with Hameroff’s theory. It may be true that you “were very clear to point out that is not proven” but pointing out that it is not proven is not the same as pointing out that it (a) does not make sense (b) does not fit with lots of reliable evidence about the brain (c) is rejected utterly by most scientists and philosophers who know about it.” And there is no way they could claim ignorance since I had explained, in the interview, the many problems with the theory.

So, in case you are wondering, why can’t quantum coherence in the microtubules explain consciousness and the NDE?

The theory first appeared in The Emperor’s New Mind by mathematician, Sir Roger Penrose (1989). Penrose argues that when mathematicians have conscious insights they are not doing ordinary computations such as might be carried out by a computer or a neural network. Instead they must be capable of handling non-computable functions. He accepts that our brains are completely controlled by physics of some kind but, he claims, it needs to be an entirely new kind of physics.

Penrose explains that there are two levels of explanation in physics; the familiar classical level used to describe large-scale objects, and the quantum level used to describe very small things. The trouble starts when you move from one to the other. At the quantum level superposed states are possible; that is, two possibilities can exist at the same time, but at the classical level either one or other must be the case. So when we make an observation at the classical level, the superposed states have to collapse into one or other possibility; a process known as the collapse of the wave function. Penrose argues that all conventional interpretations of the collapse of the wave function are only approximations, and instead proposes his own theory of “Objective Reduction”. This new process is gravitational but non-local in nature. This means that it can potentially link things in widely separated areas, making large-scale “quantum coherence” possible. Although this can only happen when the system is isolated from the rest of the environment, Penrose suggests that this might happen inside the brain – but where?

It was the American anaesthesiologist, Stuart Hameroff, who suggested that the answer might lie in structures called microtubules. He had come across evidence (subsequently found to be invalid) linking microtubules to the abolition of consciousness in anaesthesia. He reasoned that microtubules might therefore be necessary for consciousness. This was the idea that gave rise to the Penrose-Hameroff theory explained so enthusiastically in “The Day I Died”.

Microtubules are, as their name suggests, tiny tube-like proteins. Hameroff and Penrose (1996) proposed that their shape and the spiral structure of their walls might mean that quantum effects within them could be kept reasonably isolated from the outside, making quantum coherence possible. But why is this relevant to consciousness? Hameroff argues that the real problems for understanding consciousness include the unitary sense of self, free will, and the effects of anaesthesia, as well as non-algorithmic, intuitive, processing. All these, he claims, can be explained by quantum coherence in the micro-tubules. Non-locality can bring about the unity of consciousness, quantum indeterminacy accounts for free will (see Dennett 2003 for reasons why it cannot), and non-algorithmic processing, or quantum computing, is done by quantum superposition. As for NDEs, on “The Day I Died”, Hameroff explains that when the brain stops functioning, the information in the microtubules is not lost. Rather it leaks out into the universe at large and then continues to hang together by quantum coherence. This, he claims, can explain how the conscious self can be experienced as hovering above the body.

So how good is this explanation? We can begin with consciousness itself, which is conventionally equated with subjective experience. The “Hard Problem” of consciousness (Chalmers 1996) is to explain how subjective experience can arise from (or perhaps be) the objective activity of brain cells. Penrose and Hameroff’s theory has nothing whatever to say about this. If quantum computing does occur in the brain this would be very important, but it only adds another layer of complexity to the way the brain works. So we must still ask “How does subjective experience arise from objective reduction in the microtubules?” The strange effects entailed in quantum processes do not, of themselves, have anything to say about the experience of light or space or pain or colour or time.

One of the strengths of the theory is supposed to be that it accounts for the unitary sense of self, but nothing in the theory explains how to get from interacting quantum effects to the feeling that “I” am a continuing self who makes decisions and lives my life. Also, as we have seen, the theory requires that the quantum process is isolated from the rest of the environment, but a hovering self during an NDE would not be.

Several commentators have pointed out these, and many other problems. Many conclude that the theory just replaces one mystery (subjective experience) with another (quantum coherence in the microtubules)? Even people renowned for their unconventional thinking have rejected it outright, such as computer engineer and futurist Ray Kurzweil (1999). But the most devastating critique is made by philosophers Rick Grush and Patricia Churchland. They take Penrose’s argument step by step, and demolish each one.

An obvious problem is that microtubules are not specialised structures confined to brains: they occur in almost all cells of the body, in both animals and plants, and are involved in supporting the cell’s structure, in cell division, and in transporting organelles within the cell. It is true that some anaesthetics affect microtubules, but many others do not, even though they obliterate consciousness. Also drugs are known that damage the structure of microtubules but appear to have no effect on consciousness, and there is no evidence that microtubules are implicated in other major changes in consciousness, such as sleep-wake cycles.

Concerning the physics, Grush and Churchland argue that microtubules cannot provide the conditions of purity and isolation required by Penrose’s theory, nor could effects be transmitted from one microtubule to another as is required for explaining the unity of consciousness in the way Penrose requires. In addition the theory provides no explanation of how the quantum effects could interact with effects at the level of neurons, neurotransmitters and neuromodulators, when the microtubules are supposed to be isolated from their environment.

Grush and Churchland (1995) conclude that “… the argument consists of merest possibility piled upon merest possibility teetering upon a tippy foundation of ‘might-be-for-all-we-know’s… we judge it to be completely unconvincing and probably false.” (Grush & Churchland 1995 p 12). Churchland puts it even more strongly: “Quantum coherence in the microtubules is about as explanatorily powerful as pixie dust in the synapses.” (Churchland 1998, p 121).

They also ask why such a flimsy theory has proved so popular. Perhaps, they suggest, it is because some people find the idea of explaining consciousness by neuronal activity somehow degrading or scary, whereas “explaining” it by quantum effects retains some of the mystery.

Whatever the reason, the TV show proved equally palatable, and if the producers’ aim was popularity then they certainly succeeded. Most viewers want to believe in life after death and they like to see “evidence” that confirms their traditional dualism.  I accused the producers of making a dishonest programme and misleading viewers, accusations they strongly denied. Kate Broome replied that “I think we tried to at least to suggest that there are other ways of looking at this subject other than in a reductionist way”. Yes, they did. It’s just that every previous programme on NDEs has done exactly the same, giving viewers the answers they want rather than trying to find out the truth. Although we may never get to see it on TV, the real science of NDEs is much more exciting than quantum coherence in the microtubules.


Chalmers, D. (1996) The Conscious Mind, Oxford, University Press

Churchland, P.S. (1998) Brainshy: Nonneural theories of conscious experience. In S.R. Hameroff, A.W. Kaszniak and A.C. Scott (Eds) Toward a Science of Consciousness: The Second Tucson Discussions and Debates. Cambridge, MA., MIT Press, 109-124

Dennett, D.C. (2003) Freedom Evolves, New York, Penguin

Grush, R. and Churchland, P.S. (1995) Gaps in Penrose’s toilings. Journal of Consciousness Studies, 2(1), 10-29

Hameroff, S.R. and Penrose, R. (1996) Conscious events as orchestrated space-time selections. Journal of Consciousness Studies, 3(1), 36-53 (also reprinted in Shear, J. (Ed) 1997, Explaining Consciousness – The ‘Hard Problem’, Cambridge, MA, MIT Press, 177-195)

Kurzweil, R. (1999) The Age of Spiritual Machines, New York and London, Texere

Penrose, R. (1989)  The Emperor’s New Mind, London, Vintage