De La Mettrie's Ghost

Front matter

S GHOST

DE LA METTRIE’

TheS

Contents

Acknowledgements

1 Introduction

4 Free will and free won't 5 Illusions of willing

Chapter 2 | BACK TO BASICS

Free will is primarily a property of consciousness. It is something that we consciously experience ourselves enacting. So what do modern philosophy and science have to tell us about the nature of conscious experience of any type? An enormous amount has been written and speculated on the topic over the last twenty or so years, so let’s take a whistle-stop tour of the main themes — starting with philosophy.

Philosophy We think we know what consciousness is until we try to describe or define it. St Augustine said much the same about time. Perhaps the most widely accepted brief definition derives from a very influential paper by the philosopher Thomas Nagel entitled ‘What is it like to be a bat?’ written in 1974, which was one of the chief triggers for the current surge of interest in consciousness. Nagel’s definition goes: ‘consciousness is that which exists when there is something that it is like to be that thing’. You can pick the definition up in your mind, so to speak, turn it over or look at it back to front, and it still seems quite opaque. But at least, while obviously self-referential in some elusive way, it does not seem entirely circular. The problem with getting at what it means is that one soon gets lost when trying to decide for example what the ‘it’ in ‘it is like’ refers to, or whether the ‘something’ and the ‘thing’ are the same. But then the subjective essence of conscious awareness is hard to put into words, however many one uses.

A more pragmatic definition, used either implicitly or explicitly by a great many people, is: “consciousness is the difference we perceive when we awake from dreamless sleep’. It’s pretty banal, though, and not obviously helpful.

Clearly definitions alone are unlikely to take us far, and we need to look at more detailed discussions. Unfortunately, outsiders may sometimes suspect (rightly) that the opinions arrived at in these arguments are not only confusing but confused, despite the enviable intellectual gifts of many contributors. For instance, it is common for philosophical debates to include what has been called the argument from personal incredulity, i.e. ‘I can’t believe that, so it must be wrong’. Despite the difficult concepts and occasional dubious argument, it is possible to pick out some areas of agreement and to delineate some of the main schools of thought.

The most important area of agreement has to do with rejecting the belief that Cartesian (substance) dualism is a sensible way of looking at the world. In the 17th century René Descartes divided the world into two fundamentally different ‘substances’. There was, he argued, the res extensa of our bodies, brains and beyond, which comprised the material world, and the res cogitans of our intellectual, conscious selves, which was non-material. The last big name philosopher who wrote about consciousness and argued for a division of this type seems to have been Karl Popper!. Almost all now apparently agree that there is only one substance, namely matter or mass/energy, though there are still a few idealists around who suppose that the single substance is not matter but mind. ‘Substance dualism’ hardly ever gets a serious mention these days by professional philosophers, though some religious and other thinkers still go along with Descartes. Except for the remaining idealists, philosophers appear generally to have settled for materialism, but this comes in a wide variety of flavours.

The toughest-minded philosophers of all, now few in number, are the ‘eliminative materialists’. These people say that there is nothing but matter, so it is as pointless to talk about consciousness as it would be to discuss unicorns. We can ignore eliminative materialists, for our purposes, since their stance does not allow them to attach any real meaning to the experience of free will. Slightly less austere are the ‘identity theorists’, perhaps the best known of whom are the San Diego-based husband-and-wife team of Patricia and Paul Churchland. These hold that consciousness simply is the brain in action or, ifnot the whole brain, some particular activity within it yet to be elucidated. To caricature the views of identity theorists only slightly, they argue that there is not much point in talking about consciousness as such. What we should all get on with doing is identifying the brain states which are particular conscious experiences. Some of them, especially those writing in the 1980s, looked forward to a day when, instead of saying to ourselves ‘What a lovely sunset I’m seeing’, we would exclaim ‘My brain is in state WX/36/Z’ (or whatever classification had been devised). This view has softened a little over the last decade or so, due to the realisation that brains/minds are not isolated objects but are embedded in bodies and environments, which greatly influence their experience. Minds are always ‘embodied’3, to use the philosophy parlance. All the same, the notion that particular brain states equate in some way to particular conscious experiences is at the basis of most current philosophy of mind, even though not all agree with the identity theorists that the brain states simply are the experiences.

Daniel Dennett, a prolific and influential writer, looks at these problems from a rather different angle. His 1991 book, Consciousness Explained, had quite an impact, as many people understood him to be saying that consciousness is nothing more than an illusion. They were half right about what he meant, though his argument was more subtle than some of them thought. He was much impressed by empirical findings about visual consciousness, particularly those proving that some of what we feel we perceive is illusory. For instance, we are not aware of the quite large blind spot on our retinas that we all have because the visual system fills in the blank area with a sort of averaged version of its immediate surroundings. Our vision appears seamless to us, and proving to ourselves that we really do have a blind spot takes some effort. It involves drawing two small crosses a few centimeters apart on a piece of paper. The next step is to gaze at one cross, through one eye only, while moving the paper closer to one’s face. The second dot disappears when the paper is at a particular distance. Findings like this, and there are a lot of them, show that the perceptions we are conscious of are constructed by the brain. They are not some sort of photograph of what is out there. Dennett wondered whether other aspects of consciousness might also be illusory to some extent. There is in fact plenty of evidence that this is so, especially in relation to things like the apparent timing of experience. Although at one time he often did seem close to saying that consciousness as such can be regarded as an illusion, he nowadays appears to go along with the common-sense view that consciousness itself is ‘real’ in some sense, even though its content is a construct that can be regarded as illusory.

Other influential lines of thought grew out of the relationship between information and experience. Clearly there is some relationship in that our consciousness contains all sorts of information, much of it about the external world or our own bodies. We know things, but then so does a thermostat — it ‘knows’ whether a room is hot or cold. So what is the difference between our conscious knowledge and what a thermostat knows? The most radical answer to this question is ‘not much’. In this view, aka ‘pan-psychism’, absolutely everything is conscious in some way. One recent suggestion, for instance, is that the photons permeating all matter are aware*. A slightly weaker version of this position is termed ‘property dualism’ (to be distinguished from Cartesian ‘substance dualism’). Property dualists reckon that all matter and/or information has a potential for conscious awareness, which is able to manifest itself in our brains.

‘Dual aspect theorists’, on the other hand, hold that conscious experience is simply what information looks like from the inside. Normally, from a third person point of view, information is just information. In a system capable of taking a first person, subjective view of information, though, that information will be consciously experienced. Dual aspect theory, when combined with ideas about subjectivity or ‘the view from within’ as it is sometimes called, is certainly plausible. But it does share a sort of ad hoc quality with its cruder cousins, property dualism and pan-psychism. It provides an explanation of consciousness that does not really explain anything. This does not necessarily imply that the idea is useless, since much the same could be said about Newton’s concept of gravity. He simply asserted that gravitational action at a distance exists, contrary to all common sense, and this proved a very useful idea. Similarly, the assertion that consciousness is potentially an aspect of information is also seen as useful by some. On the other hand, Newton’s assertion was backed by mathematics and successful predictions of planetary motions. No analogous successes are visible, not even on the horizon, in consciousness studies. It is rather as if, having abolished Descartes’ res cogitans, philosophers on the whole could not quite cope with the consequences. They backtracked to some extent and said in effect: ‘Hey, we haven't really got rid of it. It was just lurking there in matter all the time. All we’ve done is get tid of the ontological separation between cogitans and extensa’. This suggestion does bridge the gap between goings-on in neurons and the vivid world of conscious experience, but it feels just a little too glib.

Does consciousness do anything?

Another theme that preoccupied some philosophers, especially ten or twenty years ago, is absolutely crucial to free will. This is the question of whether or not consciousness is epiphenomenal. An epiphenomenon is something associated with a process which has absolutely no effect on that process. The classic example is the whistle of a steam locomotive, which has no effect on the workings of the engine (except for a tiny power drain). A more up-to-date analogy would be the sound made by a car engine, which is entirely irrelevant as far as powering the car is concerned. Similarly, some have supposed that consciousness is an epiphenomenon of brain function, and can therefore have no effect on it. |

It’s a question that gets less discussion now than in the 1990s, perhaps because people who said ‘yes it is’ and ‘no it isn’t’ were about evenly balanced, in numbers and force of argument. Exchanges of the Tm right!’, ‘No you’re not!’ type quickly make way for more profitable discussions. One of the most cogent contributions to the debates was actually made by a physicist (Avshalom Elitzur), not a philosopher. Elitzur pointed out that consciousness cannot be purely epiphenomenal if only because it causes so much argument about the problems of consciousness! All the same, if people who argued the opposite point of view were right and consciousness is in fact epiphenomenal, any picture of free will anything like the folk psychological version would seem to be completely out of the question.

Identity theorists, who say that consciousness is some aspect of brain function, also say that it is not an epiphenomenon. The brain activity that is consciousness must inevitably be capable of affecting its own future functioning and that of the rest of the brain. Pan-psychists, property dualists and dual aspect theorists are in much the same position, since, from their points of view, it is basically a matter of semantics or relative perspective whether one refers to something as a neuronal event or as an experience. One might wonder whether dual aspect theorists have to agree with this, since they need not refer to physical events in neurons. They can confine themselves to discussing the dual aspects of information, which seems a more abstract sort of thing. But the best general definition of information is due to Gregory Bateson, a noted anthropologist and cyberneticist who died in 1980; namely ‘information is a difference that makes a difference’. The essence of an epiphenomenon is that it does not make a difference. Dual aspect theorists, too, are therefore committed to viewing consciousness as efficacious (i.e. non-epiphenomenal).

People who, like Daniel Dennett, think that consciousness is something a bit like an illusion can argue that it is not efficacious. On the other hand, few of them would deny that consciousness is either a product of, or intimately related to, neural activity of some sort — activity which must itself be efficacious. Therefore, to say that it is ineffective, while what it describes (the neural activity with which it is associated) cannot be so, amounts to little more than a semantic quibble. For all practical purposes, even if - these theorists are right in some abstract sense to distinguish consciousness from its neural entanglements, it must nevertheless be regarded as efficacious. This conclusion about the practicalities holds good unless the distinction between consciousness and brain amounts to some sort of real separability having observable and/or experiential consequences.

There are indeed thinkers, mostly on the fringes of the philosophical mainstream or beyond, who believe that consciousness can be separate from brain in a knowable way. Charles Tart, a US psychologist and parapsychologist, is an especially prominent and sensible advocate of this belief and has written extensively about his reasons for holding it. Some suggest, for example, that phenomena like out-of-body or near-death experiences may be examples of this peeling apart of mind and body. However, if they use experiential evidence of any sort to support their view, they must regard consciousness as efficacious (which they all do, so far as I know). They have to do so because the evidence depends on people’s reports of their experience. Such reports can only be made if all sorts of memory-related and other neural functions come into play. Therefore, even if consciousness is genuinely separated from the brain to some extent in the course of a near-death experience, it must still be able to affect the brain. If it had no effect, we would not know about such experiences because we would have no reports.

In short, the only philosophers who can consistently hold that consciousness is an epiphenomenon are committed to a semantic quibble, devoid of any consequences for all practical purposes. It is unfortunate that a good deal of loose talk about how consciousness may not really do anything has seeped into popular culture, helping to bolster the view that free will is a will-o’-the-wisp. There are all sorts of illusory aspects to the experience of free will, just as there are illusory aspects to any conscious experience, but one of the apparently most formidable philosophical arguments against it is groundless.

So the attribution of epiphenomenality to consciousness turns on precisely what is meant by the term ‘consciousness’. The argument can be made only if consciousness can be distinguished in some meaningful way from all neural activity of any sort. Rejection of substance dualism already makes any such claim distinctly dubious. What finally kills it is that, if the distinction were sufficiently real to allow experiential or other detection, then the argument must be untrue because detection requires that the consciousness in question be reportable in some way. This in turn means that it must have effects on the brain, even if only on memory systems and, via them, on verbal or other motor systems. In fact, as we shall see, it is precisely on memory systems that consciousness has its main impact.

What has philosophy told us?

Contemporary philosophers make many interesting points about consciousness, especially in connection with how it relates to the body it inhabits and the subtleties associated with subjectivity. Practically all agree that our form of consciousness is associated with brain activity. They disagree, often passionately, on whether it can be identified with brain activity, whether it may be some more general phenomenon that the brain taps into, whether the brain generates it in some way, and so on. Nevertheless, if pressed, nearly all accept that, if you have some particular and unique conscious experience, then there will exist some particular and unique neural state or activity that either is the conscious experience, or generates it, or at the very least closely correlates with it. Note that the reverse is not true. Only a small subset of unique neural states are associated with unique conscious states, since most neural activity is unconscious. It takes uniqueness of neural activity plus some other, unknown, ingredient to either be, or be intimately linked with, a unique conscious state. The influential modern philosopher Jaegwon Kim made the same point when he said: ‘Any two things that are exact physical duplicates are exact psychological duplicates as well’. The ‘psychological duplication’ might refer, among other things, to absence of conscious awareness or its presence.

This rather general point provides one of two main foundation stones (axioms) needed for building an adequate concept of free choice. Here it is again, more succinctly:

Any distinctive conscious experience is associated with a distinctive neural state or activity.

This statement, though derived from current philosophical opinion, is actually the basis of most present-day neuroscientific research on consciousness. It is often implicit, but Francis Crick in particular made it explicit. The research programme that he advocated involves looking for the neural activity that is most exclusively correlated with particular visual experiences. It is a programme that still has a long way to go. We can access distinctive experiences simply through introspection — seeing a red wall is a different experience from seeing a blue one, for instance, and people can report this to investigators — but we don’t know enough, or have sufficiently sensitive techniques, to distinguish the two neural states that we assume are directly associated with the two experiences, even though it would probably be just about possible with present-day techniques to tell whether someone was experiencing red or blue by examining their brain activity. Certainly it would be quite easy to tell whether they were seeing a colour or hearing a sound. But the differences we can detect at present may, for all we know, refer to unconscious aspects of perception, not conscious ones. We don’t yet know, in other words, whether the neural activities that we are able to detect are those most closely correlated with the conscious experience itself. So what do (some) scientists think about consciousness?

Neuroscience

Neuroscientific theories are even more varied, especially in their detail, than philosophical ones. It is often not clear how much different theories overlap, or even whether some may or may not be mutually exclusive. But common themes stand out. Perhaps the largest theme, a sort of Amazon among the various rivers of thought, is that consciousness has to do with recurrent, self-referential nerve activity.

Douglas Hofstadter gave the self-referential part of the package a huge boost in his 1979 book, Gédel, Escher, Bach: An Eternal Golden Braid. The book caught the imaginations of numerous people, including many of the brain scientists who were then just beginning to think about what sort of thing consciousness could be. In it, Hofstadter describes the wonders of J. S. Bach’s music, M. C. Escher’s lithographs and Kurt Gédel’s mathematical proof that there are true arithmetical theorems that can never be proved arithmetically. All these seemingly very disparate achievements crucially double back on themselves, so to speak: one part refers to the whole and vice versa. Using a very nice parable about a ‘conscious’ ant colony, Hofstadter implies that consciousness itself relies on similar self-reference. There are two main suggestions as to how this self-reference could occur in the brain.

The suggestion that attracted most attention at first has to do with recurrent loops of nervous activity between sub-cortical centres in the brain and the cerebral hemispheres, called cortico-thalamic loops. Erich Harth’s 1993 book The Creative Loop: How the Brain Makes a Mind gives an especially readable account of this type of model. Anatomists have certainly found these loops and there is evidence that they are important to functions closely associated with consciousness, particularly attention itself. Recently, however, many researchers have relegated such loops to a supporting role. The discovery that, when separate brain areas are dealing with a single percept, such as looking at a friend’s face, their electrical activity is often synchronised? led many neuroscientists to suspect that intra-cortical circuitry might be the basis for consciousness. Cortico-thalamic loops may help other feedback loops to trigger cortical synchronisations. Others, notably the Nobel Prize winner Gerald Edelman, hold that ordinary recurrence is not strong enough to provide the sort of unified basis that consciousness needs. They argue that ‘re-entrant’ nerve activity is required. This involves sets of feedback circuits, in which the information in one set is constantly and reciprocally updated from the information in others.

Another idea that has a lot of evidence going for it is that consciousness is a function of a ‘global workspace’. This is the view that San Diego-based psychologist Bernard Baars, in particular, advocates. The picture here is that lots of specialised, but unconscious, mental modules process information. They constantly compete for access to the hub of a centralised distribution network. The winning modules get to have their information distributed to all the others. This ever-changing, widely shared information is the stream of consciousness in this model.

Many neuroscientists picture consciousness as being divisible into a sort of background, general capacity for conscious awareness, and a variable number of more specific facilities. Self-awareness is always among these. The conscious T tends to be viewed as an amalgam of neural self-models in the brain with aspects of its emotional and stabilising functions. Some single out language as being fundamental to a specifically human capacity for consciousness.

Today’s most popular de la Mettrie concept of the brain likens it to a computer. Descartes himself pictured the brain as an hydraulic machine while, early in the 20th century, people often compared it to a telephone exchange or endorsed Sir Charles Sherrington’s famous analogy with an ‘enchanted loom’. There is a bit less enthusiasm for the computer analogy now than there was ten or twenty years ago, mainly because of the embarrassing discovery that Artificial Intelligence is hard to achieve. Brains can easily do things that are difficult or impossible for computers. Despite recent leaps in technology, recognising individual faces from different angles and in changing light conditions, for instance, is still hard for computers but easy for us. In fairness, even we have trouble recognising faces upside down. The brain, neuroscience now concedes, cannot be very like any of our present-day computers. Nevertheless there must be something in the analogy since both brains and computers process information, while consciousness contains an ever-changing stream of information about all sorts of things, not unlike the data on the screen of a working laptop. There is, therefore, a lot of interest in how the brain encodes information, particularly conscious information.

Nerve cells transmit information to one another by electrical and chemical activity. In many respects the electricity and the chemistry are two sides of the same coin: electrical changes arise from, and influence the movement of, chemical ions. Christof Koch, who worked with Francis Crick for many years, described in 1999 how there are 14 separate mechanisms within individual neurons that could undertake computation. It’s not known how many of these mechanisms are actually important. Nevertheless, individual brain cells are certainly far more sophisticated than the transistors in a computer.

There is another layer of computation over whatever is confined to individual cells. This relates to communication networks between cells. The first transmission mechanism to be discovered, still often viewed as the most important, involves action potentials, all-or-nothing electrical waves that sweep along nerve fibres. These can trigger the release of more than fifty neurotransmitter or neuromodulator chemicals, which may in turn cause an action potential in another neuron or modify its probability of firing. Information is certainly coded in the frequency of action potentials and is probably often also coded in their timing, independently of overall frequency.

Neurons communicate in other ways also. For example, some cells release hormone-like substances into the bloodstream which affect other parts of the brain. Local diffusion of various chemicals can play a part as well. Waves of varying calcium concentration spreading through support cells can affect nearby nerve cells. Nitric oxide, a gas which can diffuse quickly through the brain over short distances, may be important too®. Local electrical fields are probably significant, particularly in affecting the finest nerve endings, called dendrites. Indeed, although cell membranes normally insulate the innards of nerve cells from one another, there are direct electrical connections, called gap junctions, in some places that aid the spread of electrical fields. The densest concentration of these is between dendrites belonging to different neurons.

All these mechanisms relate to how the brain may deal with information. Their connection, if any, with consciousness, is unclear. As we will see shortly, there is only indirect evidence about how the information in consciousness itself might be encoded. It seems unlikely that conscious experience could be directly based on things like the frequency with which some particular neuron fires, since it normally relates to higher level, more integrated, brain functions. That is not to say that the firing of an individual neuron can never register in consciousness, since this probably can happen sometimes. For instance, recordings taken from parts of the brain that recognise particular faces or places show that very few neurons seem to be responsible — and we are of course conscious of things of this sort. Moreover direct electrical stimulation of just a few cells can sometimes produce a conscious experience. All the same, an individual cell can be expected to register by virtue of affecting some extensive property or activity involving many neurons. Few people hold that an isolated nerve cell could be conscious.

Much of what happens in the brain seems to be poised on the borderline between order and chaos. Edge-of-chaos systems have a fractal structure and are widespread in the brain at all sorts of functional levels, from the anatomy of dendrites, through the electrical activity of whole brains, to some aspects of the organisation of cognitions. Systems like this are often very sensitive to small inputs: activity in a single nerve cell can sometimes trigger a big change in the state of the whole system. But it is the state of the whole, or at least of some part of it much larger than the single neuron, that is likely to relate most directly to consciousness.

So it is understandable, against this background, that Walter Freeman and his colleagues, working in California in the 1980s, found evidence that what rabbits are conscious of smelling relates to the pattern of electrical chaos in their olfactory lobes. Freeman gave his rabbits something to smell while measuring the electrical field changes in the parts of their brains that process information about odours. Interestingly enough, the same smell (meaning the same odorant applied to the rabbit’s nose) never gave rise to exactly the same type of chaotic activity twice, though there were more similarities in the activity with the same smell than with a completely different smell. This suggested that rabbits’ consciousness might be encoded in chaotic activity in some fairly direct manner. After all, we ourselves do not have identical experiences in response to identical stimuli — think of the difference between smelling new-baked bread when you are hungry and when you have eaten too much — and maybe rabbits are like us in this respect.

Quantum mind theories

A completely different line of scientific speculation about consciousness is that it might have some quantum theoretical basis. Physicists signed up to the traditional Copenhagen interpretation of quantum mechanics, needed to understand what conscious observers really are, since these play a central part in their theories about matter. Conscious observers ‘collapse the wavefunction’ in the Copenhagen view, resulting in an object being observed in just one of its possible states; they are thus responsible for either killing or reprieving Schrédinger’s famous cat. Other theorists’ felt that quantum field theory might provide a solution to the binding problem: how disparate activities in the brain are unified into a single conscious experience. Yet others had the vague feeling that, since both quantum theory and consciousness are great mysteries, they must be connected.

Interest in quantum mind theories peaked in the early 1990s, probably due mainly to Roger Penrose’s book The Emperor’s New Mind, published in 1989. This is a fascinating popular account of fundamental physics and its possible connections with mind, by a very eminent mathematical physicist who, among many other achievements, worked with Stephen Hawking on the theory of black holes. Today the quantum theories of mind are no longer the hot topic that they were. More physically plausible solutions to the binding problem have been suggested. People are now less interested in the Copenhagen interpretation of quantum mechanics. Conscious observers have largely lost their central role in fundamental physics to an automatic process called decoherence. Furthermore, the growing body of research on quantum computation has made people think it very unlikely the brain could use any such mechanism. It seems far too fragile to survive such a warm, wet, messy environment.

None of these objections absolutely rules quantum theory out of consciousness. That it might have a role is still being actively investigated. One of the main theories® involves quantum effects acting in structures inside neurons called microtubules. Other suggestions are that fields of exotic quantum particles of various types may affect brain function?. Many of these ideas are highly technical and difficult to follow for most neuroscientists, untrained in quantum field theory. It is fair to say that there is no convincing empirical evidence in favour of any of the quantum theories of mind. So far.

What neuroscientists do