Conscious Entities

This paper  by Pais-Vieira, Lebedev, Kunicki, Wang, and Nicolelis has attracted a great deal of media attention. The BBC described it as ‘literally mind-boggling’. It describes a series of experiments in which the minds of two rats were apparently melded to act as one.

Or does it? One rat, the ‘encoder’ was given a choice of levers to push – left or right (in some cases a more rat-friendly nose-activated switch was used instead of a lever). If it selected the correct one when cued, it got a reward in form of a few drops of water (it seems even lab rats are not getting the rewards they used to these days). Some of the rats learned to pick the right lever in 95% of cases and these went on to the next stage where the patterns of activation from their sensorimotor cortex as they pushed the right lever were picked up and transmitted.

Meanwhile ‘decoder’ rats had been fitted with similar brain implants and trained to respond to a series of impulses delvered in the same sensorimotor area by pressing the right lever. In this training stage they were not receiving impulses from another rat, just an artificially produced stream of blips. This phase of training apparently took about 45 days.

Finally, the two rats were joined up and lo: the impulses recorded from the ‘encoder’ rat, once delivered to the brain of the ‘decoder’ rat, enabled it to hit the right lever with up to 70% accuracy (you could get 50% from random pressing, of course, but it’s still a significant improvement in performance). In one pointless variation, the encoder and decoder rats were in different labs thousands of miles apart; so what? Are we still amazed that electrical signals can be transmitted over long distances?

A couple of other aspects of the experiments seem odd to me. They did not have a control experiment where the signals went to a different part of the decoder rat’s cortex, so we can’t tell whether the use of the particular areas they settled on was significant. Second, they provided the encoder rat with incentives: it got water only when the decoder rat got it right. What was that meant to achieve, apart from making the encoder rat’s life slightly worse than it already was? In essence, it encourages the encoder rat to develop effective signals: to step up the clarity and strength of the neural signals it was sending out. That may have helped to make the experiment a success, but it also detracts from any claim that what was being sent was normal neural activity.

So, what have we got, overall? Really, nothing to speak of. We’re encouraged to think that the decoder rat was hearing the encoder’s thoughts, or feeling its inclinations, or something of the kind, but there’s clearly a much simpler explanation baked into the experiment: it was simply responding to electric impulses of a kind that it had already been trained to respond to (for 45 days, which must be the rat equivalent of post-doctorate levels of lever-pushing knowledge).

Given the lengthy training and selection of the rats, I don’t think a 70% success rate is that amazing: it seems clear that they could have got a better rate if, instead of inserting precise neural connections, they had simply clipped an electrode to the decoder rat’s left ear.

There’s no evidence here of direct transmission of cognitive content: the simple information transferred is delivered via the association already trained into the ‘decoder’. There’s no decoding, and no communication in rat mentalese.

The discussion in the paper ends with the following remarkable proposition.

 …in theory, channel accuracy can be increased if instead of a dyad a whole grid of multiple reciprocally interconnected brains are employed. Such a computing structure could define the first example of an organic computer capable of solving heuristic problems that would be deemed non-computable by a general Turing-machine. Future works will elucidate in detail the characteristics of this multi-brain system, its computational capabilities, and how it compares to other non-Turing computational architectures…

Well, I’m boggling now.

I have been reading about the Brain Preservation Foundation (BPF), which hopes that chemical and other methods, including a refined version of plastination, will enable brains to be preserved with such fidelity that memories, personality, and even identity can be preserved.

This may well seem reminiscent of the older cryogenic preservation projects which have not always had a good press over recent years, though they still continue to operate and indeed have refined their processes somewhat. But although the BPF also has a vision of bringing people back to life after their natural death, it is in many ways a different kettle of fish. It does not itself offer any kind of service but merely seeks to promote research, and it does not expect to see a practical system for many years. In addition, it makes its case and addresses objections in a commendably clear and thoughtful way – see for example this blog post by John M Smart, co-founder of the BPF. Perhaps this is partly also to do with its impressive panel of advisors, which includes such names as Chalmers, Seung, and Eagleman, to mention only a few.

I have some reservations about the project, which fall into several categories; there are general concerns about the practicality of preservation, doubts about personal identity, and doubts about the claimed social value of letting people have a prolonged or renewed life; but there are positive factors, too.

There are clearly a lot of technical issues involved in preserving a brain (often said to  be the most complex object in the universe) in all its detail, most of which I’m not competent to assess.  I think the main general practical issue (if this counts as practical) is that although you might get a quite different impression from the popular press, we still don’t really have a really clear idea of how the brain works – so in preserving it it’s hard to know whether we’re getting the right features. Clearly we would want the neuronal structure preserved in fine detail; but we keep finding out more about such matters as the incredibly complex sets of neurotransmitters that make the system work, about electrical interactions, and about the actual and possible role of astrocytes. If we’re optimistic we may feel we’re close to a working picture, but then we felt like that about genetics until the human genome was sequenced, and it’s now becoming increasingly clear that we didn’t know the half of it. Even without considering whether there might after all be something in the Penrose/Hameroff theory of unknown quantum mechanics operating in microtubules, or in similar ideas from outside the mainstream, there is a lot to think about. Of course the BPF can justly say that it is well aware of these issues , that  they only reinforce the need for more research, and that working on preservation could well be a good way of pushing that research forward.

I think it’s conceivable that there are also problems waiting to be discovered at a deeper level and that the brain can’t even theoretically be ‘frozen’ in working shape – particularly if mental activity turns out to be inherently dynamic. This could happen in a couple of general ways.  First, the brain could be like a zero-gravity box full of bouncing and colliding balls. You can’t halt the activity in such a box and restart at an arbitrary point: you have to start at the point where the balls were thrown in. Second, the brain could be like the old astronomical clocks which were geared together in such a way that they could not be reset; if they ever ran down and stopped, the only way to put them right again was to rebuild them. If either of these issues affects the brain, then it could not be restarted from its state at the last moment of consciousness, but only from some earlier state which might be a few minutes back, a few weeks, or in the worst case, the moment of birth! Now most of us would not mind losing just the last few minutes of our life if it meant we could then live on indefinitely, but even if that’s all it amounts to, recreating that earlier viable state from the later one we had preserved might be extremely difficult – if that’s the game we’re in.

The good news on that is that all the empirical evidence suggests there is no such problem. People have come back from states in which brain activity had apparently run down very close to zero without any major long-term problem: so we can probably afford to be optimistic that a stopped brain is not a dead brain ipso facto.

More of a problem (perhaps) is the BPF’s hope that preserving the brain might preserve personal identity. The philosophical literature on personal identity stretches back many centuries and I seem to remember that my own earlier self had some sophisticated views on it. As an undergraduate I think I developed a kind of morphic neo-nominalist position which dealt with nearly all the issues; but over the years I have become a caveman and my position now is more or less:  see this? this rock – rock is rock – what your problem? To put it another way I think brute physical identity is essential to personal identity.

I’m aware, of course, that the atoms and molecules of our body are constantly changing – but so what? Why should we think reality resides at the most micro level? Those particles barely have identities themselves; they’re more than half-way towards being mere mathematical constructions. People always say there’s a good chance we’re all breathing the odd molecule of oxygen that was once in the nostrils of Julius Caesar, but how would we know? Can you label a molecule? Can you recognise one? Can you even track where it goes? If I put three on a packing case, can you pick out the one you chose earlier? Isn’t it part of the deal that two protons have identical attributes, apart from their spatial co-ordinates? They’re not so much things as loci. Does talking about the same/different molecule, then, mean anything much? No, reality does not reside exclusively at the molecular level and I rest my case instead on the physical identity of certain neural structures, irrespective of their particle content. We are those critical neurons, I think.

Now you might think that the BPF is off to a flying start with me here, because instead of proposing to upload my mind onto magnetic media, they’re aiming to preserve the echt physical neurons. But I do not think they are optimistic about the prospects of literally restarting the self-same set of neurons: rather they adopt a ‘patternist’ view in which it’s the functional pattern of your mind that carries your identity. I doubt that: for one thing it seems to mean there could be as many of you as there are copies of the pattern. However, the strange thing is, I don’t think the majority of people will actually care: rightly or wrongly they’ll be just as happy with the prospect of a twin – really a kind of hyper-twin, far more like you than any real-life twin – as they would be with their own identity. Hey, they’ll say, I’m not really the same person I used to be ten years ago anyway, any more than you are the same person as that callow young morphic ne0-nominalist. Perhaps when we are in the unprecedented situation of being able to copy ourselves our conception of identity must naturally change and loosen, though as we ontologists say, the idea certainly gives me the willies.

There’s another deep problem in becoming immortal: I might run out. As it is, old people sometimes seem to repeat themselves or get stuck in a groove. Perhaps there comes a natural point when really you’ve said and thought everything important you’re ever going to say and think, and any further lifespan is just going to be increasingly stale repetition. Perhaps the price of acquiring a really fresh lot of mental plasticity is, frankly, being a new person. I have once or twice met older people who, while fit and mentally agile, seemed to feel that the job of their life was basically complete, and while they didn’t specially want to die, there wasn’t really that much detaining them any more, either. It’s a common observation, moreover, that old people sometimes seem to repeat themselves or get stuck in a groove.

I don’t really know how far the idea of people ‘running out’ is true or how far failing memory and appetite for fresh exploration might simply be the product of waning vigour and physical energy, of a kind the BPF might hope to rectify (if rectification is the appropriate term). However, it does seem likely that even if it were true different people would run out at different stages, and probably few of us have completely exhausted our potential by the time we’ve done three score and ten.  George Bernard Shaw took the view that three hundred years would be about the optimum lifespan, and it does feel like a comfortable benchmark: so even if there are natural limits to how far we should go on, it might be good to have the option of another couple of centuries.

That brings us on to the social benefits which the BPF suggests might accrue from having older minds around. They suggest that these older minds would be liberal and enlightened, and a force for progress, [Correction: John M. Smart has very courteously pointed out that the BPF doesn't suggest this at all. I don't quite know where I picked up the idea from, but I apologise for the error] which seems to fly in the face of many generations of experience, which is that old people tend to be increasingly conservative. Old scientists whose theories have been refuted don’t usually give them up: they merely die in due course, still protesting that they were right, and make way for a new generation.

If one comes from a culture that reveres certain ancestors, the the prospect of being able, as it were, to bring back Benjamin Franklin to put the Supreme Court right on a couple of points about the Constitution might look pretty appealing; but how many subjects are the oldies going to be experts on?  You may think now that you’re a pretty hip grandpa for understanding Facebook: in fifty years, are you going to have any grasp at all of what’s going on in a society mediated by electronic transactions on systems that haven’t even been conceived of yet?

The good news here is that if the BPF is right, future generations will be able to take the old people out and put them away again as required like library books. Your future life may turn out to be a series of disconnected episodes several hundred years apart. You may find yourself now and then waking up in worlds where your senatorial views on certain matters are valued, but don’t count on having the vote, if such a thing still exists in recognisable form.

All in all, it can’t be bad to reward research, and it certainly can’t be bad to think about the issues, which the BPF also does a good job on, so I wish them plenty of luck and success.

Dan Dennett confesses to a serious mistake here, about homuncular functionalism.

An homunculus is literally a “little man”. Some explanations of how the mind works include modules which are just assumed to be capable of carrying out the kind of functions which normally require the abilities of a complete human being. This is traditionally regarded as a fatal flaw equivalent to saying that something is done by “a little man in your head”; which is no use because it leaves us the job of explaining how the little man does it.
Dennett, however, has defended homuncular explanations in certain circumstances. We can, he suggests, use a series of homunculi so long as they get gradually simpler with each step, and we end up with homunculi who are so simple we can see that they are only doing things a single neuron, or some other simple structure, might do.

That seems fair enough to me, except that I wouldn’t call those little entities homunculi; they could better be called black boxes, perhaps. I think it is built into the concept of an homunculus that it has the full complement of human capacities. But that’s sort of a quibble, and it could be that Dennett’s defence of the little men has helped prevent people being scared away from legitimate “homuncular” hypotheses.

Anyway, he now says that he thinks he underestimated the neuron. He had been expecting that his chain or hierarchy of homunculi would end up with the kind of simple switch that a neuron was then widely taken to be; but he (or ‘we’, as he puts it) radically underestimated the complexity of neurons and their behaviour. He now thinks that they should be considered agents in their own right, competing for control and resources in a kind of pandemonium. This, of course, is not a radical departure for Dennett, harmonising nicely with his view of consciousness as a matter of ‘multiple drafts’.

It has never been really clear to me how, in Dennett’s theory, the struggle between multiple drafts ends up producing well-structured utterances, let alone a coherent personality, and the same problem is bound to arise with competing neurons. Dennett goes further and suggests, in what he presents as only the wildest of speculations, that human neurons might have some genetic switch turned on which re-enables some of the feral, selfish behaviour of their free-swimming cellular ancestors.

A resounding no to that, I think, for at least three reasons. First, it confuses their behaviour as cells, happily metabolising and growing, with their function as neurons, firing and transmitting across synapses. If neurons went feral it is the former that would go out of control, and as Dennett recognises, that’s cancer rather than consciousness. Second, neurons are just too dependent to strike out on their own; they are surrounded, supported, and nurtured by a complex of glial cells which is often overlooked but which may well exert quite a detailed influence on neuronal firing. Neurons have neither the incentive nor the capacity to strike out on their own. Third, although the evolution of neurons is rather obscure, it seems probable that they are an opportunistic adaptation of cells originally specialised for detecting elusive chemicals in the environment; so they may well be domesticated twice over, and not at all likely to retain any feral leanings. As I say, Dennett doesn’t offer the idea very seriously, so I may be using a sledgehammer on butterflies.

Unfortunately Dennett repeats here a different error which I think he would do well to correct; the idea that the brain does massively parallel processing. This is only true, as I’ve said before, if by ‘parallel processing’ you mean something completely different to what it normally means in computing. Parallel processing in computers involves careful management of processes which are kept discrete, whereas the brain provides processes with complex and promiscuous linkages. The distinction between parallel and serial processing, moreover, just isn’t that interesting at a deep theoretical level; parallel processing just a handy technique for getting the same processes done a bit sooner; it’s not something that could tell us anything about the nature of consciousness.

Always good to hear from Dennett, though. He says his next big project is about culture, probably involving memes. I’m not a big meme fan, but I look forward to it anyway.

This 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…

Back in November Human Rights Watch (HRW) published a report - Losing Humanity – which essentially called for a ban on killer robots – or more precisely on the development, production, and use of fully autonomous weapons,  backing it up with a piece in the Washington Post. The argument was in essence that fully autonomous weapons are most probably not compatible with international conventions on responsible ethical military decision making, and that robots or machines lack (and perhaps  always will lack) the qualities of emotional empathy and ethical judgement required to make decisions about human lives.

You might think that in certain respects that should be fairly uncontroversial. Even if you’re optimistic about the future potential of robotic autonomy, the precautionary principle should dictate that we move with the greatest of caution when it comes to handing over lethal weapons . However, the New Yorker followed up with a piece which linked HRW’s report with the emergence of driverless cars and argued that a ban was ‘wildly unrealistic’. Instead, it said, we simply need to make machines ethical.

I found this quite annoying; not so much the suggestion as the idea that we are anywhere near being in a position to endow machines with ethical awareness. In the first place actual autonomy for robots is still a remote prospect (which I suppose ought to be comforting in a way). Machines that don’t have a specified function and are left around to do whatever they decide is best, are not remotely viable at the moment, nor desirable. We don’t let driverless cars argue with us about whether we should really go to the beach, and we don’t let military machines decide to give up fighting and go into the lumber business.

Nor, for that matter, do we have a clear and uncontroversial theory of ethics of the kind we should need in order to simulate ethical awareness. So the New Yorker is proposing we start building something when we don’t know how it works or even what it is with any clarity. The danger here, to my way of thinking, is that we might run up some simplistic gizmo and then convince ourselves we now have ethical machines, thereby by-passing the real dangers highlighted by HRW.

Funnily enough I agree with you that the proposal to endow machines with ethics is premature, but for completely different reasons. You think the project is impossible; I think it’s irrelevant. Robots don’t actually need the kind of ethics discussed here.

The New Yorker talks about cases where a driving robot might have to decide to sacrifice its own passengers to save a bus-load of orphans or something. That kind of thing never happens outside philosophers’ thought experiments. In the real world you never know that you’re inevitably going to kill either three bankers or twenty orphans – in every real driving situation you merely need to continue avoiding and minimising impact as much as you possibly can. The problems are practical, not ethical.

In the military sphere your intelligent missile robot isn’t morally any different to a simpler one. People talk about autonomous weapons as though they are inherently dangerous. OK, a robot drone can go wrong and kill the wrong people, but so can a ballistic missile. There’s never certainty about what you’re going to hit. A WWII bomber had to go by the probability that most of its bombs would hit a proper target, not a bus full of orphans (although of course in the later stages of WWII they were targeting civilians too).  Are the people who get killed by a conventional bomb that bounces the wrong way supposed to be comforted by the fact that they were killed by an accident rather than a mistaken decision? It’s about probabilities, and we can get the probabilities of error by autonomous robots down to very low levels.  In the long run intelligent autonomous weapons are going to be less likely to hit the wrong target than a missile simply lobbed in the general direction of the enemy.

Then we have the HRW’s extraordinary claim that autonomous weapons are wrong because they lack emotions! They suggest that impulses of mercy and empathy, and unwillingness to shoot at one’s own people sometimes intervene in human conflict, but could never do so if robots had the guns. This completely ignores the obvious fact that the emotions of hatred, fear, anger and greed are almost certainly what caused and sustain the conflict in the first place!  Which soldier is more likely to behave ethically: one who is calm and rational, or one who is in the grip of strong emotions? Who will more probably observe the correct codes of military ethics, Mr Spock or a Viking berserker?

We know what war is good for (absolutely nothing). The costs of a war are always so high that a purely rational party would almost always choose not to fight. Even a bad bargain will nearly always be better than even a good war. We end up fighting for reasons that are emotional, and crucially because we know or fear that the enemy will react emotionally.

I think if you analyse the HRW statement enough it becomes clear that the real reason for wanting to ban autonomous weapons is simply fear; a sense that machines can’t be trusted. There are two facets to this. The first and more reasonable is a fear that when machines fail, disaster may follow. A human being may hit the odd wrong target, but it goes no further: a little bug in some program might cause a robot to go on an endless killing spree. This is basically a fear of brittleness in machine behaviour, and there is a small amount of justification for it. It is true that some relatively unsophisticated linear programs rely on the assumptions built into their program and when those slip out of synch with reality things may go disastrously and unrecoverably wrong. But that’s because they’re bad programs, not a necessary feature of all autonomous systems and it is only cause for due caution and appropriate design and testing standards, not a ban.

The second facet, I suggest, is really a kind of primitive repugnance for the idea of a human’s being killed by a lesser being; a secret sense that it is worse, somehow more grotesque, for twenty people to be killed by a thrashing robot than by a hysterical bank robber. Simply to describe this impulse is to show its absurdity.

It seems ethics are not important to robots be cause for you they’re not important to anyone. But I’m pleased you agree that robots are outside the moral sphere.

Oh no, I don’t say that. They don’t currently need the kind of utilitarian calculus the New Yorker is on about, but I think it’s inevitable that robots will eventually end up developing not one but two separate codes of ethics. Neither of these will come from some sudden top-down philosophical insight – typical of you to propose that we suspend everything until the philosophy has been sorted out in a few thousand years or so – they’ll be built up from rules of thumb and practical necessity.

First, there’ll be rules of best practice governing their interaction with humans.  There may be some that will have to do with safety and the avoidance of brittleness and many, as Asimov foresaw, will essentially be about deferring to human beings.  My guess is that they’ll be in large part about remaining comprehensible to humans; there may be a duty to report , to provide rationales in terms that human beings can understand, and there may be a convention that when robots and humans work together, robots do things the human way, not using procedures too complex for the humans to follow, for example.

More interesting, when there’s a real community of autonomous robots they are bound to evolve an ethics of their own. This is going to develop in the same sort of way as human ethics, but the conditions are going to be radically different. Human ethics were always dominated by the struggle for food and reproduction and the avoidance of death: those things won’t matter as much in the robot system. But they will be happy dealing with very complex rules and a high level of game-theoretical understanding, whereas human beings have always tried to simplify things. They won’t really be able to teach us their ethics; we may be able to deal with it intellectually but we’ll never get it intuitively.

But for once, yes, I agree: we don’t need to worry about that yet.

Sue Pockett is back in the JCS with a new paper about her theory that conscious experience is identical with certain electromagnetic patterns generated by the brain. The main aim of the current paper is to offer a new hypothesis about what distinguishes conscious electromagnetic fields from non-conscious ones; basically it’s a certain layered shape, with negative charge on top followed by a positive region, a neutral one, and another positive layer.

Pockett sets the scene by suggesting that there are three main contenders when it comes to explaining consciousness: the thesis that consciousness is identical with certain patterns of neuron firing; functionalism, the view that consciousness is a process; and her own electromagnetic field theory. This doesn’t seem a very satisfactory framing. For one thing it doesn’t do much justice to the wild and mixed-up jungle which the field really is (or so it seems to me); second there isn’t really a sharp separation between the first two views she mentions – plenty of people who think consciousness is identical with patterns of neuronal activity would be happy to accept that it’s also a neuronal process. Third, it does rather elevate Pockett herself from the margins to the status of a major contender; forgiveable self-assertion, perhaps, although it may seem a little ungenerous that she doesn’t mention that others have also suggested that consciousness is an electromagnetic field (notably Johnjoe McFadden – although he believes the field is causally effective in brain processes, whereas Pockett, as we shall see, regards it as an epiphenomenon with no significant effects).

Pockett mentions some of the objections to her theory that have come up. One of the more serious ones is the point that the fields she is talking about are in fact tiny and very local: so local that there is no realistic possibility of the field from one neuron influencing the activity of another neuron. Pockett is happy to accept this; conscious experience doesn’t actually have the causal role we usually attribute to it, she says: it’s really just a kind of passenger accompanying mental processes whose course is determined elsewhere. She cites various people in support of this epiphenomenalist view, including Libet – she has some interesting things to say about his experiments (but doesn’t note that he too liked the idea of a mental field of some kind).

The new thesis about the shape of conscious fields appears to spring from observation of neuronal structure in the neocortex, and in particular the fact that in its fourth layer there are no pyramidal cell bodies. This is a feature which appears to be characteristic of the parts of the neocortex often associated with consciousness, and it implies that there is a gap or neutral region in the fields generated there, helping to yield the layered structure mentioned above. Pockett proposes a number of experiments which might support her view, some of which have already been carried out.

So what do we make of that? I see a number of problems.

First is the inherent implausibility of the overall theory. Why on earth would we identify conscious experience with tiny electromagnetic fields? I think the attraction of the theory comes from thinking about two kinds of consciousness, more or less the two kinds identified by Ned Block: the a-consciousness that does the work of useful, practical cogitation, and the p-consciousness which simply endows it with subjective feeling. Looked at from this angle it may be appealing to think that the actual firing of neurons is doing the a-consciousness while the subjectivity, the phenomenal experience, come from the subsidiary electric buzz.

But when we look at it more closely, that doesn’t make any particular sense. The problem is that conscious experience doesn’t seem like anything in physics, whether a field or a lump of matter. If we’re going to identify it with something physical, we might as well identify it with the neurons and simplify our theory – dropping the field entity in obedience to Occam’s Razor. Nothing about the electrical fields helps to explain the nature of phenomenal experience in a way that would motivate us to adopt them.

Second, there’s the problem of Pockett’s epiphenomenalism. Epiphenomenalism is very problematic because if consciousness does not cause any of our actions, our reports and discussions about it cannot have been caused by it either. Pockett’s own account of consciousness could not have been caused by her actual conscious experience, and nothing she writes could be causally related to that actual experience: if she were a zombie with no consciousness, she would have written just the same words. This is a bit of an uncomfortable position in general, but it also means that Pockett’s ambitions to test her theory experimentally are doomed. You cannot test scientifically for the existence of a supposed entity that has no effects because it makes no observable difference whether it’s there or not. All of Pockett’s proposed experiments, on examination, test accessible aspects of her theory to do with how the fields are generated by neurons: none of them test whether consciousness is present or absent, and on her theory no such experiment is possible.

While those issues don’t technically prove that Pockett is wrong, they do seem to me to be bad problems that make her theory pretty unattractive.

The first working brain simulation? Spaun (Semantic Pointer Architecture Unified Network) has attracted a good deal of interested coverage.

Spaun is based on the nengo neural simulator: it basically consists of an eye and a hand: the eye is presented with a series of pixelated images of numbers (on a 28 x 28 grid) and the hand provides output by actually drawing its responses. With this simple set up Spaun is able to perform eight different tasks ranging from copying the digit displayed to providing the correct continuation of a number sequence in the manner of certain IQ tests. Its performance within this limited repertoire is quite impressive and the fact that it fails in a few cases actually makes it resemble a human brain even more closely. It cannot learn new tasks on its own, but it can switch between the eight at any time without impairing its performance.

Spaun seems to me an odd mixture of approaches; in some respects it is a biologically realistic simulation, in others its structure has just been designed to work. It runs on 2.5 million simulated neurons, far fewer than those used by purer simulations like Blue Brain; the neurons are essentially designed to work in a realistic way, although they are relatively standardised and stereotyped compared to their real biological counterparts. Rather than being a simple mass of neurons or a copy of actual brain structures they are organised into an architecture of modules set up to perform discrete tasks and supply working memory, etc. If you wanted to be critical you could say that this mixing of simulation and design makes the thing a bit kludgeish, but commentators have generally (and rightly, I think) not worried about that too much. It does seem plausible that Spaun is both sufficiently realistic and sufficiently effective for us to conclude it is really demonstrating in practice the principles of how neural tissue supports cognition – even if a few of the details are not quite right.

Interesting in this respect is the use of semantic pointers. Apparently these are compressions of multidimensional vectors expressed by spiking neurons; it looks as though they may provide a crucial bridge between the neuronal and the usefully functional, and they are the subject of a forthcoming book, which should be interesting.

What’s the significance of Spaun for consciousness? Well, for one thing it makes a significant contribution to the perennial debate on whether or not the brain is computational. There is a range of possible answers which go something like the following.

1. Yes, absolutely. The physical differences between a brain and a PC are not ultimately important; when we have identified the right approach we’ll be able to see that the basic activity of the brain is absolutely standard Turing-style computations.
2. Yes, sort of. The brain isn’t doing computation in quite the way silicon chips do it, but the functions are basically the same, just as a plane doesn’t have flapping feathery wings but is still doing the same thing – flying – as a bird.
3. No, but. What the brain does is something distinctively different from computation, but it can be simulated or underpinned by computational systems in a way that will work fine.
4. No, the brain isn’t doing computations and what it is doing crucially requires some kind of hardware which isn’t a computer at all, whether it’s some quantum gizmo or something with some other as yet unidentified property  which biological neurons have.

The success of Spaun seems to me to lend a lot of new support to position 3: to produce the kind of cognitive activity which gives rise to consciousness you have to reproduce the distinctive activity of neurons – but if you simulate that well enough by computational means, there’s no reason why a sufficiently powerful computer couldn’t support consciousness.

There’s an interesting conversation here with Noam Chomsky. The introductory piece mentions the review by Chomsky which is often regarded as having dealt the death-blow to behaviourism, and leaves us with the implication that Chomsky has dominated thinking about AI ever since. That’s overstating the case a bit, though it’s true the prevailing outlook has been mainly congenial to those with Chomskian views . What’s generally taken to have happened is that behaviourism was succeeded by functionalism, the view that mental states arise from the functioning of a system – most often seen as a computational system. Functionalism has taken a few hits since then, and a few rival theories have emerged, but in essence I think it’s still the predominant paradigm, the idea you have to address one way or another if you’re putting forward a view about consciousness. I suspect in fact that the old days, in which one dominant psychological school – associationism, introspectionism, behaviourism – ruled the roost more or less totally until overturned and replaced equally completely in a revolution, are over, and that we now live in a more complex and ambivalent world.

Be that as it may, it seems the old warrior has taken up arms again to vanquish a resurgence of behaviourism, or at any rate of ideas from the same school: statistical methods, notably those employed by Google. The article links to a rebuttal last year by Peter Norvig of Chomsky’s criticisms, which we talked about at the time. At first glance I would have said that this is all a non-issue, because nobody at Google is trying to bring back behaviourism. Behaviourism was explicitly a theory about human mentality (or the lack of it); Google Translate was never meant to emulate the human brain or tell us anything about how human cognition works. It was just meant to be useful software. That difference of aim may perhaps tell us something about the way AI has tended to go in recent years, which is sort of recognised in Chomsky’s suggestion that it’s mere engineering, not proper science. Norvig’s response then was reasonable but in a way it partly validated Chomsky’s criticism by taking it head-on, claiming serious scientific merit for ‘engineering’ projects and for statistical techniques.

In the interview, Chomsky again attacks statistical approaches. Actually ‘attack’ is a bit strong: he actually says yes, you can legitimately apply statistical techniques if you like, and you’ll get results of some kind – but they’ll generally be somewhere between not very interesting and meaningless.  Really, he says, it’s like pointing a camera out of the window and then using the pictures to make predictions about what the view will be like next week: you might get some good predictions, you might do a lot better than trying to predict the scene by using pure physics, but you won’t really have any understanding of anything and it won’t really be good science. In the same way it’s no good collecting linguistic inputs and outputs and matching everything up (which does sound a bit behaviouristic, actually), and equally it’s no good drawing statistical inferences about the firing of millions of neurons. What you need to do is find the right level of interpretation, where you can identify the functional bits – the computational units – and work out the algorithms they’re running. Until you do that, you’re wasting your time. I think what this comes down to is that although Chomsky speaks slightingly of its forward version, reverse engineering is pretty much what he’s calling for.

This is, it seems to me, exactly right and entirely wrong in different ways at the same time. It’s right, first of all, that we should be looking to understand the actual principles, the mechanisms of cognition, and that statistical analysis is probably never going to be more than suggestive in that respect. It’s right that we should be looking carefully for the right level of description on which to tackle the problem – although that’s easier said than done. Not least, it’s right that we shouldn’t despair of our ability to reverse engineer the mind.

But looking for the equivalent of parts of  a Turing machine? It seems pretty clear that if those were recognisable we should have hit on them by now, and that in fact they’re not there in any readily recognisable form. It’s still an open question, I think, as to whether in the end the brain is basically computational, functionalist but in some way that’s at least partly non-computational, or non-functionalist in some radical sense; but we do know that discrete formal processes sealed off in the head are not really up to the job.

I would say this has proved true even of Chomsky’s own theories of language acquisition. Chomsky, famously, noted that the sample of language that children are exposed to simply does not provide enough data for them to be able to work out the syntactic principles of the language spoken around them as quickly as they do (I wonder if he relied on a statistical analysis, btw?). They must, therefore, be born with some built-in expectations about the structure of any language, and a language acquisition module which picks out which of the limited set of options has actually been implemented in their native tongue.

But this tends to make language very much a matter of encoding and decoding within a formal system, and the critiques offered by John Macnamara and Margaret Donaldson (in fact I believe Vygotsky had some similar insights even pre-Chomsky) make a persuasive case that it isn’t really like that. Whereas in Chomsky the child decodes the words in order to pick out the meaning, it often seems in fact to be the other way round; understanding the meaning from context and empathy allows the child to word out the proper decoding. Syntactic competence is probably not formalised and boxed off from general comprehension after all: and chances are, the basic functions of consciousness are equally messy and equally integrated with the perception of context and intention.

You could hardly call Chomsky an optimist: It’s worth remembering that with regard to cognitive science, we’re kind of pre-Galilean, he says; but in some respects his apparently unreconstructed computationalism is curiously upbeat and even encouraging.

Besides being the author of thoughtful comments here – and sophisticated novels, including the great fantasy series The Second Apocalypse – Scott Bakker has developed a theory which may dispel important parts of the mystery surrounding consciousness.

This is the Blind Brain Theory (BBT). Very briefly, the theory rests on the observation that from the torrent of information processed by the brain, only a meagre trickle makes it through to consciousness; and crucially that includes information about the processing itself. We have virtually no idea of the massive and complex processes churning away in all the unconscious functions that really make things work and the result is that consciousness is not at all what it seems to be. In fact we must draw the interesting distinction between what consciousness is and what it seems to be.

There are of course some problems about measuring the information content of consciousness, and I think it remains quite open whether in the final analysis information is what it’s all about. There’s no doubt the mind imports information, transforms it, and emits it; but whether information processing is of the essence so far as consciousness is concerned is still not completely clear. Computers input and output electricity, after all, but if you tried to work out their essential nature by concentrating on the electrical angle you would be in trouble. But let’s put that aside.

You might also at first blush want to argue that consciousness must be what it seems to be, or at any rate that the contents of consciousness must be what they seem to be: but that is really another argument. Whether or not certain kinds of conscious experience are inherently infallible (if it feels like a pain it is a pain), it’s certainly true that consciousness may appear more comprehensive and truthful than it is.

There are in fact reasons to suspect that this is actually the case, and Scott mentions three in particular; the contingent and relatively short evolutionary history of consciousness, the complexity of the operations involved, and the fact that it is so closely bound to unconscious functions. None of these prove that consciousness must be systematically unreliable, of course. We might be inclined to point out that if consciousness has got us this far it can’t be as wrong as all that. A general has only certain information about his army – he does not know the sizes of the boots worn by each of his cuirassiers, for example – but that’s no disadvantage: by limiting his information to a good enough set of strategic data he is enabled to do a good job, and perhaps that’s what consciousness is like.

But we also need to take account of the recursively self-referential nature of consciousness. Scott takes the view (others have taken a similar line), that consciousness is the product of a special kind of recursion which allows the brain to take into account its own operations and contents as well as the external world. Instead of simply providing an output action for a given stimulus, it can throw its own responses into the mix and generate output actions which are more complex, more detached, and in terms of survival, more effective. Ultimately only recursively integrated information reaches consciousness.

The limits to that information are expressed as information horizons or strangely invisible boundaries; like the edge of the visual field the contents of conscious awareness  have asymptotic limits – borders with only one side. The information always appears to be complete even though it may be radically impoverished in fact. This has various consequences, one of which is that because we can’t see the gaps, the various sensory domains appear spuriously united.

This is interesting, but I have some worries about it. The edge of the visual field is certainly phenomenologically interesting, but introspectively I don’t think the same kind of limit seems to come up with other senses. Vision is a special case: it has an orderly array of positions built in, so at some point the field has to stop arbitrarily; with sound the fading of farther sounds corresponds to distance in a way which seems merely natural; with smell position hardly comes into it and with touch the built-in physical limits mean the issue of an information horizon doesn’t seem to arise. For consciousness itself spatial position seems to me at least to be irrelevant or inapplicable so that the idea of a boundary doesn’t make sense. It’s not that I can’t see the boundary or that my consciousness seems illimitable, more that the concept is radically inapplicable, perhaps even metaphorically. Scott would probably say that’s exactly how it is bound to seem…

There are several consequences of our being marooned in an encapsulated informatic island whose impoverishment is invisible to us: I mentioned unity, and the powerful senses of a ‘now’ and of personal identity are other examples which Scott covers in more detail. It’s clear that a sense of agency and will could also be derived on this basis and the proposition that it is our built-in limitations that give rise to these powerfully persuasive but fundamentally illusory impressions makes a good deal of sense.

More worryingly Scott proceeds to suggest that logic and even intentionality – aboutness – are affected by a similar kind of magic that similarly turns out to be mere conjuring. Again, results generated by systems we have no direct access to, produce results which consciousness complacently but quite wrongly attributes to itself and is thereby deluded as to their reliability. It’s not exactly that they don’t work (we could again make the argument that we don’t seem to be dead yet, so something must be working) more that our understanding of how or why they work is systematically flawed and in fact as we conceive of them they are properly just illusions.

Most of us will, I think want to stop the bus and get off at this point. What about logic, to begin with? Well, there’s logic and logic. There is indeed the unconscious kind we use to solve certain problems and which certainly is flawed and fallible; we know many examples where ordinary reasoning typically goes wrong in peculiar ways. But then there’s formal explicit logic, which we learn laboriously, which we use to validate or invalidate the other kind and which surely happens in consciousness (if it doesn’t then really I don’t think anything does and the whole matter descends into complete obscurity); hard not to feel that we can see and understand how that works too clearly for it to be a misty illusion of competence.

What about intentionality? Well, for one thing to dispel intentionality is to cut off the branch on which you’re sitting: if there’s no intentionality then nothing is about anything and your theory has no meaning. There are some limits to how radically sceptical we can be. Less fundamentally, intentionality doesn’t seem to me to fit the pattern either; it’s true that in everyday use we take it for granted, but once we do start to examine it the mystery is all too apparent. According to the theory it should look as if it made sense, but on the contrary the fact that it is mysterious and we have no idea how it works is all too clear once we actually consider it. It’s as though the BBT is answering the wrong question here; it wants to explain why intentionality looks natural while actually being esoteric; what we really want to know is how the hell that esoteric stuff can possibly work.

There’s some subtle and surprising argumentation going on here and throughout which I cannot do proper justice to in a brief sketch, and I must admit there are parts of the case I may not yet have grasped correctly – no doubt through density (mine, not the exposition’s) but also I think perhaps because some of the latter conclusions here are so severely uncongenial. Even if meaning isn’t what I take it to be, I think my faulty version is going to have to do until something better comes along.

(BTW, the picture is supposed to be Thomas Aquinas, who introduced the concept of intentionality. The glasses are suppose to imply he’s blind, but somehow he’s just come out looking like a sort of cool monk dude. Sorry about that.)

My dear Wormwood,

How delightful that after so long you should again be seeking my counsel! I remain, of course, your ever-affectionate Uncle; but what a tizzy you seem to be in! I suppose it is understandable. Here you are, a junior devil – still only a junior devil, alas – and you find that the soul you have been set to ensnare has suddenly become a leading champion of the Enemy! Eben Alexander, a neurologist of good standing and therefore surely our rightful prey, has had  a near-death experience, and on his recovery has published a book sensationally claiming that he now knows the truth of the afterlife at first hand. Why me, you complain in whining tones, why does it have to be me that gets the Celebrity Christian?

Please compose yourself. As a matter of fact the situation is nothing like as bad as you suppose; in fact I will venture to say that it is excellent. In the first place you talk as though Dr Alexander had undergone a miraculous conversion, but in fact is it not the case that he was always a declared Christian? Of course, we should prefer him not to be a Christian at all, but if it must be so then a Celebrity Christian, I assure you, is the very best kind he could be. Consider, to begin with, the opportunities for that most useful sin, spiritual vanity. I say opportunities, but are we not in fact dealing with a sin which is already fully realised? The symptoms of vanity are bad enough in those people who merely insist on telling one about their dreams; this fellow believes his are a Divine revelation which we must all read about! I hardly think Dr Alexander, in the quiet of his own mind, can suppose himself to be much less than a saint – and then which of the saints could claim to have the further distinction of being a proper scientist? A neurosurgeon, to boot! He surely feels that he has been called to a high and lonely eminence. Apart from its inherently damnable qualities, this vanity will encourage a misplaced feeling of certainty and divert his attention away from the very area – his own failings and imperfections – which most need his attention. And of course it is always especially delightful when a man’s religion is the very thing that helps drag him Hellwards.

In passing we may note that while firm faith is highly adverse to our cause, a feeling of scientific certainty about God and Heaven is very helpful to us. The humans forget that faith can only exist where there is doubt (otherwise why would the Enemy leave them to work things out for themselves in that perverse manner of his?) and forget that if they behave well merely in order to get into a scientifically established Heaven, their acts are self-interested and lack true virtue. Our Lord Below once pointed out to the Enemy how well this all works for us: look, he said; to be virtuous the humans must not be acting for reward, so only someone who doesn’t believe in Heaven can really be good. Only the atheists have an opportunity of disinterested virtue  – and obviously only the believers have faith; so between the two tests virtually no-one can qualify for Paradise. No wonder, he said, that the Pearly Gates stand almost unused, disconsolate angels telling each other hopefully that surely this year a couple of people will get in, while all the time the mouth of Hell gapes and swallows, gapes and swallows, a thousand miles wide every time. I’m not asking you to concede defeat in any humiliating way, Our Father Below explained to the Enemy, all I’m saying is, be realistic – let’s get round a table on this one and see what we can work out? I regret to say, dear nephew, that these very rational and reasonable overtures were summarily rejected.

The second splendid thing about a Celebrity Christian is the scope for humbug. It’s virtually impossible for these people to be completely honest. One of Dr Alexander’s claims to a special status for his revelation is that, uniquely, it was scientifically established that his ne0cortex was entirely inactive throughout the period of his absence; established by neurological investigations and CT scans. Now as a neurosurgeon Dr Alexander must be well aware that even fMRI scans only measure neuronal activity via the proxy of blood flow (albeit it’s a fairly good one), and that CT scans don’t measure it at all, merely looking for damage and possible bleeding. The ‘neurological tests’ we may confidently take to be little more than the observation that he was unresponsive while unconscious. None of this would actually prove that his neocortex was completely inactive. Even if it were, a scientist of Dr Alexander’s standing surely knows the evidence that dreams and dream memories may be generated almost instantly at the point of awakening: they do not have to have occurred in real time. So on two counts it cannot be shown that he was having experiences while his neocortex was ‘dead’. We need not accuse him of direct dishonesty over this; but he clearly isn’t going out of his way to correct any misunderstanding  which might arise and be helpful to his case.

At the same time he realises quite well at some level that in recounting his vision he isn’t telling the strict and literal truth. Does he suppose that those high cheekbones possessed by his female guide were real cheekbones, of real bone with real marrow, fed by real blood with real haemoglobin oxygenated by contact with real air? No: if he thinks about it all (which you should discourage, by the way) he thinks the cheekbones were spiritual, or metaphorical; but he has to keep saying they were cheekbones, because if they weren’t real, why should we suppose he was really in Heaven or that any of it was actual, rather than simply a set of absurd noodlings by a man who was half conscious? Once that gap has opened up between what a man says and what he knows to be the strict truth, the beetle of humbug is in place and we can begin to force the gap wider; keep him thinking that he has to make allowances for what simpler folk can cope with, and within a few years he’ll be thinking of himself as peddling a mere metaphor for a sophisticated truth from which in fact all honesty and semblance of real religion has long since leached away. Any tiny, dangerous fragment of real mystical experience which Dr Alexander may have had will be quite lost under a heap of things he thinks it judicious or appropriate to say or think. It isn’t likely, of course, that Dr Alexander had a genuine mystical experience of any kind, even in a fleeting, momentary form, but it’s just the sort of cheating the Enemy indulges in now and then, letting the little vermin have an uncovenanted fragment of the truth in amongst the falsehoods which they actually sought out for themselves.

Of course you will want to keep Dr Alexander from realising quite how absurd his noodlings are; in this respect I think we can be proud of the work we have done within the education system.  A man  like Dr Alexander can pass right through to the highest level of academic attainment these days without ever reading Plato or encountering any of the classical texts or poetry which might enlarge his cramped imagination. If we were now to reproach such a man for expressing his vision in terms fit only for a child’s comic paper, we need no longer fear that he will apologise and try harder, or even issue a manly rejection of the triviality of our  complaint when set against the importance of his message; no, far likelier he will embark on a gratifyingly silly defence of comics as an imaginative medium and mature art form!

Naturally others, by contrast, can be encouraged to realise in full the absurdity of the noodlings: another great benefit of Dr Alexander’s intervention is the heart it will put into our friends the atheists. If this is the tosh we are up against, they’ll think, we need not work too hard. I dare say Professor Dawkins will allow himself an extra glass of port and perhaps decide he can cancel one or two of his more tedious public appearances. This is all good in two ways: first, of course we like the atheist cause to prosper; but also we like people to relax into their slogans and their easy rhetoric. We like the well-worn clichés. We don’t want anyone impelled to try a bit harder to come up with new ideas on either side.  The last thing we want is for people to be prompted into genuine fresh, open-ended thought; and I’m sure you’ll take good care that never happens with Dr Alexander’s revelations.

Your affectionate Uncle,

Screwtape

Apologies to C.S. Lewis, and to readers who notice that Screwtape’s theological acuity and literary gifts seem to be a bit below his old level. I should add Lewis’s customary warning to readers: Screwtape, like all devils, is an habitual liar and nothing he says should be taken at face value. In passing, it’s worth noting another thing about near-death experiences: materialist champions of artificial intelligence are often accused of wanting to change the meaning of certain words – ‘intelligence’, ‘learning’ and so on – to favour themselves: but it seems that some on the other side are just as bad and want to monkey with the meaning of that simple, homely old word ‘death’!

What about it, though: could our consciousness possibly survive death? There has always been rather strong evidence that consciousness arises from the activity of our brain. Stop the brain with a blow to the head and you get unconsciousness: stop it permanently with a slightly harder blow and you get death. Over the last hundred years or so the correlation has been worked out in more and more detail and the empirical evidence of exquisitely detailed correspondences is pretty overwhelming. Although we don’t yet have a scientific explanation of consciousness, the size and shape of the gap where one might go is becoming clear. In fact, I should say it’s now rather difficult to see how the kind of God envisaged by Lewis could be conscious; never having had to face the challenges of survival on the ancient savannah which presumably shaped the evolution of the human brain, and not having any neuronal apparatus, it’s becoming hard to imagine how He (or Screwtape) could possibly manage it. As a matter of fact I suspect that Lewis and his fellow Inklings had a slightly unorthodox neoplatonic conception of God which they partly kept to themselves; but that’s another subject.

We can arrive at a similar conclusion about our own physicality without being so brutally reductionist. When I sit down and think seriously about what day to day life as a disembodied spirit would be like, I find myself in some difficulty. With no eating, sleeping, walking around or working, I don’t quite know what would be left of my life. Perhaps if there is a spiritual internet I could carry on blogging: surely the discussion of the mind itself is a sufficiently immaterial activity to go on after death? Well, maybe: but my motives for doing it all seem to be based in my animal nature. Curiosity – the way the primate brain goes on demanding to be fed, whereas the feline one obligingly goes to sleep once the stomach is full – is part of it; a vague fear that I don’t basically know what is going on here (anywhere), which no doubt relates to simpler nervousnesses out on that ancestral savannah; the acquisitive pleasure of having ‘got’ something, even if only an abstract argument; they all have their roots in biology and would probably cease to influence my ghost. If so, what would that ghost amount to, and how much would it have in common with the robustly biological animal which pressed the keys to create this text?

It could still be that although our mental life arises from neuronal activity it has a spiritual dimension, but it seems to me that the contest is almost a default win for materialism because traditional dualism barely offers any view as to how spiritual consciousness actually works. An honourable exception is the theory offered by Sir John Eccles with Karl Popper; but their psychons seem to me to mirror neurons a little too closely.

There’s scope for a panpsychist theory whereby our consciousness relapses into its constituent parts after death; but although those parts would still be conscious to some degree it wouldn’t be our distinctive individual consciousness, so to my taste it’s not much better.

What then, about a thoroughly materialist survival? Could the details of our neuronal activity be recorded and then replayed in some suitable medium – or could our neurons gradually be replaced by silicon? I put aside here the Searlian theory that consciousness requires some as-yet unknown special property of neuronal tissue, because hypothetically we can grow artificial neuronal tissue and use that if it’s really necessary. My concerns here are to do with identity. It might be possible to replay an exact copy, but a copy isn’t me; and if I gradually get replaced, won’t I be gradually phased out in a similar way? The fact that I might never know it and might be replaced by a very similar individual is not really enough. I put aside here also the idea that neuronal replacement is theoretically impossible, that the process of neuronal interaction is such that for esoteric reasons it cannot be stopped and restarted or bits replaced; although that’s an interesting hypothesis it doesn’t look as if things work like that.

It does look, though, as if our essential neurons never do get replaced in the normal course of events. We do actually correspond in relatively simple physical terms to a definite set of neurons that last us our whole life; and when they go, we go. Without proving anything absolutely, I think that gives quite a bit of weight to my fears about the effect of substitution on my identity.

It’s not life after death, but what, for the sake of completeness, about just going on as we are: what about getting that same set of neurons to last forever? Let us, as Woody Allen put it, not live on through our work, but live on through not dying. I don’t know why that should be impossible, but I suspect it is. It is noteworthy that remaining young and fit indefinitely should surely have the best possible survival value; yet all the large organisms produced by evolution die. It looks as if we’re up against some fundamental constraint.

My own conclusion is that death is indeed inevitable, final, and definitive. That is an unpleasant prospect, but perhaps when I am grown up I will at last be calm and clear enough about it to be able to tell the assorted merchants of immortality what I think is actually the final truth; one good life is enough.