Jonathan C.W. Edwards
Conscious experience has been said to be outside of, or alien to, physics, and unexplained in a physical world. However, it is argued here that experience is entirely expected in a physical world that can only be defined by its power to determine patterns of experience. Something physical is something with the type of causal power that can contribute to determining the content of an experience if a subject is present at the right place and time. Physical powers also interact with other physical powers, distant from any given subject, to form chains, and it is these interactions that physics handles mathematically. Nevertheless, actual causation is always defined by reference to determination of experience. The apparent puzzle of why there should be a link between experience and the physical may relate in part to the fact that experience is always immediately causally proximal, always ‘from here’, at least as far as we can ascertain. Proximality, and with it the potential for mentality, cuts across existential/ontological categories. Experience also requires a concept of an intrinsic individual, in order for there to be individual points of view. The practical problem for consciousness studies is to identify intrinsically individual causal units forming proximal event domains that can have appropriate points of view, in human brains or elsewhere, in a way consistent with current physics.
At the centre of debate about the nature of consciousness is the relation between our experience and the world that physics aims to describe – taken by most to equate to the physical world (but see Strawson, 2006). Experience is used here to imply what is commonly called subjective, first person, or phenomenal experience, or ‘feel’, with features that may be called qualia (Nagel, 1974).
It has been claimed that experience is somehow alien to, or outside, physics and that its existence can be considered unaccounted for in a world describable by physics (Chalmers, 1995). However, there is something odd about this claim, since observation, which nobody has encountered in the absence of experience, is the gold standard by which all physics is ultimately calibrated. This suggests a closer relation between experience and physics than popular views of physics allow. A closer relation has been argued repeatedly by philosopher-scientists at least since the sixteenth century and credit has been given for highlighting it to Russell (1927) and, in particular, Eddington (1927), in the introduction to The Nature of The Physical World. In the context of recent attempts to relate experience to specific brain processes it may be helpful to review what it is that physics is actually about, and what we mean by a physical world, before assuming that there is a puzzle to sort out.
Despite Eddington’s reminder of the Enlightenment insight that the nature of the physical world can only ever be something inferred indirectly from its power to determine mental patterns, popular dogma in both philosophy and science was largely ignoring his message by the late twentieth century. (Later chapters of Eddington’s book suggest that even he may have missed the full significance of his introductory remarks.) Philosophy of mind increasingly focused on a debate about the existence of an ‘explanatory gap’ between physics and experience (Levine, 1983). Some denied the existence of such a gap. However, apart from Chomsky (2000), most who did so (e.g. Dennett (1991)) seemed to deny that experience was even something that merited consideration in its own right. Neither side considered experience as essential to a definition of a physical world. Within neuroscience a deflationary approach to experience, as something not meriting study, became widespread teaching, and this has only recently begun to change.
The deflationary approach was billed as the legitimate scientific position. Yet both the physiology of perception and fundamental physics were reinforcing the truth of Eddington’s point – that everything we think we know about the nature of the physical world is based on the phenomenal signs that parts of our brains use to signal to other parts what is going on. The ‘hardness’ of the stone Dr Johnson is supposed to have kicked (Alexander, 2000) is something manifest in a mental event, with a very indirect relation to any events involving the stone.
Definitions of the physical
Those unfamiliar with the debate may consider it obvious what the physical world is – whatever is actually there or has actually happened. But if asked whether an experience of remembering the need to buy groceries actually happened, and is therefore physical, they might backtrack. Strawson (2006) says that we should respect this simple definition and therefore should regard experiences as physical. That may well be a justified stance, but it is not the way many people use the term physical.
Three definitions of the physical are in common usage.
1. The standard dictionary definition: that which we have experience of through sense of touch or sight, rather than from within.
2. The definition used in physics: the natural causal powers, and their instances of manifestation as events, that predictably determine the patterns of our observations/experiences.
3. The intuitive definition as expressed by Dr Johnson: – the concept of stuff that makes a stone prove hard when kicked that proves Berkeley’s idealism wrong: “I refute it thus!”.
As they stand, these all end up as epistemic definitions – definitions in terms of how we can know the physical, and in terms of how it influences experience. That would not, however, capture the motivation for the intuitive definition: that we can expect there to be a more intrinsic, ontological, ‘physicality’, lying behind, intended in 3 and perhaps in 1.
The epistemic nature of definitions might be an artefact of practicalities. Dictionaries might be forced to use epistemic placeholders in the absence of an opportunity for a demonstrative mode of reference as in ‘I refute it thus’. Similarly, a physics definition might be expected to be epistemic because it grounds a method of gathering knowledge. Even recounting Dr Johnson’s claim might have to be epistemic because of being secondhand. On the other hand, the extra ingredient available if we had been at the scene to see the kicking would have been … the way the event influenced our experience.
The elusive intuitive concept of intrinsic physicality is central to the claim that experience might have no place in it, and the possibility of justifying such a concept will be returned to. Before doing so, an attempt will be made to formulate a reasonably watertight version of the epistemic definition made use of in physics and explore some of the implications.
A Formal Epistemic Definition of the Physical
The following definition of physical, as used in physics, is suggested:
The physical world consists of those types of chains of causal interactions (events) that we expect to determine predictable patterns of experience proximally in human observers if placed at specified points in space and time, however indirect or complex the chain back to any particular event of interest.
Understanding of causal interaction has changed as physics has changed but it is intended here in the general sense that we expect certain types of goings on to be followed by other types of goings on in a predictable way. The specification of types of causal chain is intended to make clear that for the mediators of some event to be physical it is not necessary for any human being to observe that event. It is only necessary that the event should be of a type that would be predicted to contribute in a certain way to the pattern of experience of a human subject at the right place and time. For the concept of the physical to be generalised we want a definition not in terms of being ‘knowable’ but in terms of being of a type, token examples of which may be known about under favourable conditions.
The reference to causal chains also implies that there is indeed more to being physical than the power to determine patterns of experience. It includes the power to take part in causal chains. Practical physics is mostly concerned with this ability to form chains. Most physics brackets out the events within human brains that finally determine patterns of experience at the proximal ends of causal chains by calibrating terms against patterns of experience we agree a description of, such as matching an object’s length to a ruler or a time lapse to the position of clock hands. Nevertheless, if we ask what we mean by the power to take part in physical causal chains it remains that we have no answer other than that it is a type of power defined by the chains’ ability to contribute to determining patterns of experience.
Put differently, to be physical can be said to be more than purely mathematical only in the sense that it implies the sort of power that can be expected to contribute to the determination of patterns of experience if an observer is in the right place at the right time. To ‘actually happen’ is to have the potential to influence experience.
In the past there has been discussion about whether to be physical is simply to be ‘observable’, rather in line with the dictionary definition, and, if so, what to do about ‘unobservables’ (see Chakravartty, 2017). Individual electrons might be regarded as unobservable – even more so the gluons of nuclei, or dark matter. These things are posited in physics because they have the power to contribute to determination of our patterns of experience, but how they do that may be subtle. As for dark matter, it may involve inference of existence from mismatch in complex calculations, but that still means that we conclude that dark matter influences our patterns of experience and in a dramatic way.
Moreover, although it might seem that we observe elephants but not electrons, our ‘seeing’ of an elephant is entirely due to detecting electrons. We infer the presence of an elephant from finding more electrons in some places than others. The idea that when we see we directly observe ‘physicality’ does not hold good. Do we see light? When a room is ‘flooded with light’ 99.999% of the light is invisible, despite going right past our noses. Do we just see illuminated walls or do we see a tiny proportion of the light reflected off those walls? There are no simple answers because the verb ‘to see’ has a muddled meaning. It conflates a range of physical processes. Unless we keep hold of the complex pathways involved, we get false arguments.
In a similar vein, it is interesting that the dictionary tends not to define the physical in terms of what we can hear or smell. We have more clues to the indirectness of these modes of knowing and perhaps for that reason they are not as intuitively associated with ‘physicality’. We hear thunder but are not sure what thunder is. We smell stale cigarette smoke where there are neither cigarettes nor smoke… and so on.
Being physical need not equate to ‘observability’ in an intuitive sense, merely to the power to influence patterns of experience in some way. Similarly, the ‘objectivity’ of being able to agree on how we classify our experiences does not detract from the fact that ultimately, when we record observations, we are classifying subjective experiences.
Is there a valid basis for a non-epistemic account of the physical?
We are used to the idea of epistemic definitions as placeholders for more intrinsic ontological concepts. Do we have reason to think that we can have a coherent conception of a more intrinsic nature to the physical beyond being the type of entity or event that can influence our patterns of experience?
The difficulty such a proposal faces is that, however framed, it can only draw on the language of signs used by the brain to conceive a distal world. That is not to suggest that a distal world only exists in experience. We can still believe that there is some intrinsic nature to the physical independent of that language. It is just that any attempt to ’get closer’ to it, like Eddington’s off-target suggestion that matter is mostly empty space, never leaves the language of mental representation. Moreover, there is little motivation for saying it would be surprising for this intrinsic nature to lead to experience. After all, all we know about it is that, at least sometimes, it does.
The more we are drawn to intuitive concepts of the physical the more we are drawn to features of experience. All intuitively ‘physical’ aspects of the world like hardness and heaviness are only known to us as dispositions to produce certain experiences. There is no basis for thinking the world is ‘really hard’ or ‘really heavy’ in another sense. To attempt to consider what something is ‘really like’, without reference to whom it is really like something to, i.e. from what point of view it is like that, is to commit a category mistake. All such attempts are nothing more than imaginings of what the something might be like as an experience for a hypothetical ‘fly on the wall’ subject or perhaps a ‘God’s eye’ or through an imaginary alphascope or gammascope or omegascope. Imagining a proton billiard ball being attracted to an electron is just such a pretence, and like Eddington’s empty space a misleading ‘pseudo-likeness’.
The idea of unknowable intrinsic features underlying dispositions takes us nowhere new. Knowing is recognising the patterns of disposition. We know of no other sort of knowledge that is somehow denied us. Stoljar (2006) has argued that the puzzlement about the association of experience with the physical arises because we know too little about the physical. Perhaps the answer is simpler; in broad terms we know all that needs to be known. Searching for more is simply going around in a loop. The problem may be more that we have an unrealistic conception of knowing.
As a caveat, it may be important not to expect ‘qualia’ to do all the work. To say that any conception of an intrinsic nature of the physical must be framed purely in qualia such as redness and loudness is too restrictive. Amodal perception, such as the sense of the unseen back of a book, indicates that the internal language the brain uses for its concepts goes beyond ‘raw qualia’. Our sense of movement, of the size of things at different distances and of properties like ‘belonging to’ all indicate that our concepts involve abstractions and categorisations beyond raw qualia. Nevertheless, as both Leibniz (1686) and Kant (1781) understood, our conceptions of both ‘secondary’ and ‘primary’ qualities, including space and time, are constructed within. If there is a correspondence to the world in these constructs it lies in some useful partial and indirect isomorphism. Our more complex concepts like ‘object’ or ‘belonging’ might perhaps take us nearer to intrinsic features of the physical world. However, the history of science suggests that these concepts are unlikely to be reliable indicators of fundamental reality. Just like qualia, they may mostly take us away from the intrinsic, into our language of useful representation.
No Need to Mind the Gap
The intuition that behind any description based on knowing there is some ‘intrinsic stuff’ to be found probably relates to the common expectation to find origins of dispositions to influence our experiences by looking inside or ‘reducing to parts’. Science may be seen as typical of this exploration, but reduction to parts may be a significant misrepresentation of what physics does today. You do not find out anything more about the mass of a rock by breaking it up. It remains a disposition to attract the earth or resist force. Similarly, charge on an electrode is not explained by charge on electrons, it is merely described at another scale. Physics tracks causal powers at whatever scale is most helpful. It does not explain powers by reduction.
Put another way, it might seem to be more of a puzzle that events inside my brain might generate the appearance, for whatever is ‘me experiencing’, of a tree falling in a storm than for a tree falling in a storm to generate the appearance of a tree falling in a storm. Physics might seem to explain why a tree falling looks the way it does but not why events inside my brain, involving cells passing messages to each other, should appear as a falling tree to ‘me’. The intuition behind this involves a misconception. Physics provides no such explanation for why the sky appears blue or large things appear large, any more than a dictionary explains why ‘dog’ means dog. In both cases the answer probably lies in some arbitrary quirk of the evolution of nervous systems or language. (There are constraints on what languages are workable but within a wide range.)
All physics does is tease out the mathematical regularities amongst powers to influence our experiences. It assumes, as Leibniz (1714) did, that there are ‘sufficient reasons’ for everything we experience: reasons that determine the regularities we call laws of nature. It gives no explanations as to why the reasons are the way they are, other than pointing out where alternatives entail contradictions. It may suggest that the reason a cork floats is the same as the reason a stone sinks, but it gives no explanation for that reason applying.
It is difficult, therefore, to see how we can complain of an ‘explanatory gap’ between the physical and experience – because there are no explanations to have a gap between. The dispositions of components of the physical world to form causal chains and the dispositions of those chains to determine the content of experience are equally unexplained. Moreover, if we think of the ‘why?’ question in terms of what might make physics and experience fit together in a parsimonious and harmonious way, then we have the opposite of a gap. The one thing that physical components of causal chains have in common is that they can link to patterns of experience. In other words, it is perverse to ask why physical events should give rise to experience. What is called a gap is more of a bridge.
There is of course a gap in our knowledge of the rules governing the way physical events within the brain determine particular patterns of experience; we have no idea of the correlations between proximal interactions and experiential contents, like the taste of peppermint. That, however, is a correspondence rule gap, not an explanatory gap. There may remain a sense that the correspondence is remarkable and hard to conceive a principled basis for. This will be returned to in the final section.
Experience as the proximal
Although I could define the physical as that which could influence my patterns of experience here, we want a more general rule for the relation of the physical to experience such that there can be experiences for others over there.
This raises an issue that may have received too little attention in discussion of consciousness – what counts as here, and its importance to experience. An event may be said to be experiential or mental only to the extent that it is considered as if immediately proximal. My mentality is always here and now. My prior mental events can be said to have been mental when immediately proximal but now are only vicariously mental as recalled elements of a mental event here and now.
The distinction between mental and physical is often considered as if these were properties that obtain irrespective of the point of view of consideration. Yet this is not how we find things. Only the event here and now, immediately proximal, is ever manifestly mental. Being mental is like the referents of words like today and next. Being mental is not an intrinsic property in any usual sense. It may be a relational property but that too may be misleading because an event can be considered to have the same relations to other things whether it is proximal or distal. Perhaps the ‘explanatory gap’ arises simply from a failure to appreciate that this further categorical divide alters the truth values of statements in a way that we cannot afford to ignore.
The distinction between proximal and distal events, or entities, has a lot in common with the distinction between first and third person accounts. In both cases we accept that the same event can be covered by either category, depending on circumstances. The first person/third person distinction is, however, problematic in a number of ways. It may assume enduring entities in the form of persons, which may not equate to proximality. It is also a distinction with no specific link to physics itself, whereas proximal and distal can be defined within physics. Specifically, in this particular context, distal implies causally prior. The physical is that which has the sort of power that can determine the content of an experience to which it is causally prior.
The Scope of Experience Within the Definition of Physical
The crucial difficulty in defining the physical in terms of the power to determine patterns of experience is that although we want to be able to generalize from the experience here, now, to a general rule, by definition, there is no test for experience other than here and now. We could stick with solipsism (or something more extreme in which the only unequivocal experience is this one here, now) but defending solipsism for ‘others’ is rather pointless. We want an account that at least acknowledges experience for others in the discussion, at whatever time or place they may be.
Panpsychism is the next simplest approach, and perhaps the most reasonable, but, being largely untestable, even using circumstantial evidence, it may do no more work than solipsism in helping us to a practical definition of the relation between experience and the physical.
A third option is special pleading for a limited range of events, perhaps most often found in nervous systems, but maybe in all cellular life forms, being the only ones to be associated with experience at least in a form recognizable as belonging to the same category as ours. Experience would then be considered to occur at least where physical causal powers are operating closely similar to those here and now (whether for the author or readers).
The objection to special pleading is that we need some justification for giving certain events special status. If, for instance, we think that experience ‘emerged’ with the emergence of certain biological events then there has to be some justification for such a concept. Detailed discussion is beyond the scope of this text, but modern field theory does suggest that new types of action or event involving novel forms of dynamic relation arise in the context of matter ordered in a complex way (see e.g. Aitchison and Hey, 2004), and biology can provide that order. The collective excitation modes proposed by Craddock et al. (2017) in neuronal cytoskeleton are interesting examples. (This is not related to putative emergence of dynamic properties in complex systems but rather the emergence of new dynamic entities in ordered condensed matter structure.)
The objection to special pleading may, therefore, be accommodated by what might be called an agnostic polypsychic approach. This accepts that the truth of panpsychism is unknowable. It accepts that certain events within biological systems, considered as proximal points in physical causal chains, can be taken as associated with experience. We have reason to think the pattern of any such experience is closely determined by physical causation. We can then propose that there is an unknown spectrum of events involving certain types of causal relation that are associated with an experiential aspect more or less similar to a human experience depending on certain parameters of the physics of the causation of the event.
It might be questioned as to what justifies suggesting that experience should be contingent on the operation of any particular physical causal powers. Two reasons can be given. Firstly, if we have already defined physical causal powers in terms of tendency to determine the content of experience they would seem to be, a priori, the right sort of contextual factors. Secondly, we have a wealth of evidence indicating that the instances of experience reported by human beings correlate, both in content and in terms of presence or absence, in great detail with proximal physical processes in the brain. To an extent, evidence based on reports is problematic because changes in brain physics might interfere with reporting rather than experience. Nevertheless, all sorts of accounts of altered states of experience, including hypnagogic states, dreams, illusions due to sensory deprivation, and various pathological states, suggest that at least the form of experiences is tightly tied to physical processes in the brain.
Note that in this account there is no reference to enduring objects that might be persons or rocks or octopuses: just to events. Physics has moved away from classical concepts of objects and deals with units of action, or in common parlance, events. The occupancy of an electron orbital is an action or event, not a ‘particle’ in the sense of an enduring object. The proposal is that if the final event in a causal chain is of the sort that is associated with experience in human brains then, for the mediators of that causal chain to be regarded as physical, by definition there will be such an experience. If not, we have no reason to judge the notional chain to be physical in a consistent sense.
A Problem for Zombies with Here and Now
The philosopher’s zombie was posited as a means of illustrating the claim by Chalmers (1995) that the existence of experience in association with physical events is somehow unexpected or surprising. The definition of the physical discussed above suggests that it is not. Nevertheless, Chalmers’s claim has been that it is at least conceivable that experience might not have been part of the physical world.
The status of the philosopher’s zombie, considered in terms of the suggested definition of the physical, is quite complicated. The hypothetical zombie, including its brain, in molecular detail, is physically identical in type to a sentient human being, but supports no experiences. That implies that the causal chains that mediate the continued existence of the zombie have the power to determine the content of the experiences of any human being that might wish to study the zombie, via conversation or MRI scan, yet do not have the power to determine the content of experience proximally, within the zombie itself, at the end of causal chains in a brain identical in type to those that determine content of experience for the rest of us.
Can this incomplete power to determine contents of experience count as physical identity as defined by the normal powers attributed to physical processes? The philosopher’s zombie is deemed ‘physically identical’ to us in a sense that invokes power over distant experiences but denies such power over itself. There must be a strong case that it is not reasonable to describe the philosopher’s zombie as physically identical to us (in type) if the defining feature of the physical does not apply within its own domain. If being physical is to be considered grounded in some internal essence then surely, even more so, the first test of that essence would be that it applies to itself, with knock-on effects elsewhere as secondary.
The challenge of the philosophical zombie is said to be that because it is conceivable to have something physically identical to us but without experience such an entity is theoretically possible. However, if physical identity entails having its own experience, by dint of having the powers we call physical, then this claim fails on the grounds of being self-contradictory. A chemical mixture that is 50% oxygen, 50% hydrogen and 50% carbon is not conceivable because percentages are defined as adding up to 100, not 150. A triangle with four angles is not conceivable. In the same way a philosopher’s zombie does not look to be conceivable.
The philosopher might counter this by saying that, OK, the powers of the zombie’s brain are different from those of ordinary physical things, but it is still physically the same. Yet this is no good, because, as indicated, we have no other way to define the physical than in terms of its powers.
Wider Categories of Mental Events
Although there is a widespread use in philosophy of mind of ‘mental’ to imply experiential, the dictionary circumscription of physical allows for a wider range of events to fall outside the physical, and traditionally under ‘mental’. The common usage of ‘mental events’ can include processes that we assume occur within the functioning brain but which are inaccessible to experience, as in the process that presents us with 18 when we ask ourselves what 6 x 3 is. These events are not known to us through our senses. Nor are we directly acquainted with them. Their existence is something we infer.
There is an epistemic difference between experientially mental events and other events that may help to explain why they seem so different, and why Davidson (1970) claimed that experiential mental events cannot be framed in the same way as physical events, even if they are part of the same sort of goings on. In a sense we are only half-acquainted with experiential events because we know of the pattern that is experienced but we have no knowledge of the way in which that pattern influences the behaviour of whatever it is experienced by, because we have no idea what the latter is. In contrast, physical events are described in terms of both an influence and what is being influenced. Predictions are made on the basis of laws of interaction where we know about both components.
Being non-experiential, mental arithmetic-type events resemble physical events epistemically (even if often poorly known) and are treated as such in neurobiological research. The way cells respond to correlations in incoming signals, as shown by Hubel and Wiesel (1959), suggests that we are dealing with ordinary physics. Yet they are also in the broader sense mental. Does the narrower experiential class of mental event overlap with the broader class and to what extent? The most obvious response is that experiential events are those that are immediately proximal to and directly involve whatever biological unit is a human experiencing subject. Mental arithmetic type events are then those events that being within the brain are closely prior to these immediately proximal events but not immediately proximal in themselves. They provide the final inferential or computational mechanisms that result in the signal content that we experience.
In other words, we use ‘mental’ both to cover proximal events in the broad sense of further in than our sense organs and in the more specific experiential sense that appears to be restricted to the most proximal event in a chain.
Mental Events: Continuum or Discrete?
The distinction between ‘experiential mental’ and ‘computational mental’ events begs an important question about events in general within a physical world. Are they discrete or do they form a dynamic continuum? Even the proposed distinction itself is called into question by certain ‘enactive’, ‘extended’ or ‘embodied’ theories of experience in which experience is seen as arising from a chain of interactions not only within the brain but going out into the environment (e.g. Noë, 2006).
What does physics have to say about this? Physics assumes a causal sequence in which there are events that are completed and no longer ‘happening’ once others have started. Traditional physics does not stipulate exactly how we should individuate events – it allows any analysis that proves reliable. In contrast, modern physics holds that events are discrete at the fundamental level – quanta of action. Individual events or actions come into being with a probability of doing so determined by asymmetries in pre-existing universal fields of potentials. Actions are not point-like, as ‘particles’ might be thought to be, but have domains in spacetime that can be of any size. Large scale (individual) actions, moreover, are not ‘built up’ from smaller actions but come into being in response to large scale asymmetries. As mentioned previously, the concept of reduction to parts has always been misleading and is now recognized as such.
How often this fundamental individuation is relevant to biology is a matter of contention, but this does not diminish a useful conclusion that modern physics allows us to draw: events or actions are fundamentally discrete, and whenever steps in a sequence are ascertainable or determinable, they can be considered as discrete. Moreover, only the most proximal ascertainable step is ever necessary to the determination of the pattern of an experience found in an observation. The causal powers of all antecedent steps relevant to this experience are passed on by the most proximal ascertainable influences. This is reflected in the common concept that these events ‘no longer exist’ or at least ‘no longer operate’. The tensed use of ‘exist’ might be considered illusory in a Minkowski block universe but that need not alter its validity in the sense of events in a temporal order not operating simultaneously.
From an empirical standpoint, an event of experience, here, now, does not stretch back into prior events as a continuum. An experience of light reflected off a chair includes nothing about events of nuclear fusion in the sun generating the light. It only tells us about the chair because the brain has learnt that it can assume certain relations are not changing and that it is therefore allowed to infer (in an operational sense) the presence of a chair from comparing a large number of inputs across the retina and across time.
Perhaps most significantly, the experience does not include anything relating to very recent events in the retina, optic nerve, superior colliculi or early visual cortex that are necessary antecedents to the formation of a coherently experienced scene. It is sometimes said that our experience of objects in the world is transparent, but it might be more accurate to describe it as opaque, because all but the final mediating event is unavailable to experience. All we are consciously acquainted with is based on signals indicating the final complex inferences that our brains draw from multiple signals from different sources.
In practice this means that you can get the same experience by replacing prior causal connections with a range of others as long as they lead to the same pattern of final connection. We take this for granted in our analysis of our observations of external events and it is why scientific experiments must be carefully controlled if we want to infer earlier events in a chain from later ones. It is also of crucial importance to the way we consider causal connections inside the brain. If these obey the same rules as events outside brains, then we cannot ascribe to earlier events in a chain effects that operate over and above those of the later events in the same chain which they have caused.
All the evidence we have suggests that the rule that the content of an experience depends only on the last ascertainable pattern of causal connection applies within the nervous system, as would be consistent with the empirical observations indicated above. As far as we know what we perceive visually is more reliably determined by what happens in the retina than what happens at the cornea (there may be a cataract), what happens in the geniculate bodies determines experience more reliably still, what happens in primary visual cortex even more reliably. The detail of what can be tested for may get more limited but as far as we can ascertain all these sensory pathways could be replaced by implants that simulated incoming signals and that no difference in experience would be discernible as long as causal connections to final events of experience are equivalent.
It is interesting to consider what things would be like if the content of an experience was not entirely determined by the immediately prior causal relation. We could expect events in one part of the brain to determine experiences at distant sites or distant times in a way over and above that of the known causal chain of neural connection. A completely new set of dynamic rules would need to be invented, together with some explanation as to why these new rules should apply within a brain. Worse still, it is hard to see how one could avoid an infinite regress in time.
In contrast to this analysis, enactive or extended views hold that experience arises from a complex sequence of events involving motor output and sensory feedback that are somehow fused into the basis of a single event of experience by belonging to an ‘embodied agent’. Yet experiments like those involving the rubber hand illusion show that the boundaries of the putative unifying embodied agent can readily be violated. There is no supernatural ‘personal agency’ to do the necessary event fusion. There is no ‘magical membrane’ (Hurley, 2006) around a human body that overrides the normal rules of physics. We know that, in general, distal events can be swapped around arbitrarily while maintaining exactly the same experience proximally, as long as the proximal signals end up being the same. In this regard, enactive and extended mind theories propose that experience arises from physical events in a way that is incompatible with everything we know about the relation of the physical to experience otherwise. If, as argued, we already have empirically validated rules relating experience to distal causal chains from throughout science then it is very hard to justify grafting on a mechanism that violates these rules.
A Physical Framework That Entails Experience Proximally
In summary, we have every reason to believe that the relation between experience and physical events, however far in to the nervous system we go, obeys a rule that applies in all science – the content of an experience is entirely necessarily and sufficiently determined by the most proximal ascertainable event in a physical causal chain. All prior events operate through the final proximal interaction and any further role would be an overdetermination. Our experience is free of any content arising directly from these prior events, and in particular those within the brain.
This leads to a general view of a world constituted by a network of chains of physical events that entail the possibility of our type of experience, and very likely a range of more or less similar phenomena, for some final proximal event if the level of order of the substrate of the final event is fitting.
All physical events have to earn their physicality through being part of a network of chains of similar events. There is no useful sense in which an isolated event is ‘physical’. To be physical is to be part of a causal network. That network may be describable in terms of a continuum of causal powers expressed in terms of fields of potentials, but it also has to be considered as segmented into individuated events or actions. Without this individuation there is no way to delimit proximality or to explain why one experience has different content from another.
Whether or not we should insist that a true individual event is by definition a quantum of action, precisely as defined in current field theory, may not be easy. In particular, quantisation and individuation of higher order collective modes of action found in condensed matter is not a simple issue. There may be a lot more to learn about identity and higher order modes. This perhaps the area of physics undergoing most rapid change. Nevertheless, both classical and modern physics agree that where events can be allocated to an ascertainable or determinable sequence, they can be considered to be distinct, and therefore individuated. Everything we know so far suggests that the ‘mentality’ of an experience draws its content from a single immediately proximal event and excludes all prior events.
This view of the entailment of experience within the physical itself involves a serious ascertainment problem, not dissimilar to that found in fundamental physics. The study of an individual event is likely to involve perturbations that make it a different event from that which one wished to study. That poses a pretty hard problem if we want to understand how physical interaction translates to qualia in an individual proximal event. But it is a logistic rather than a metaphysical problem. Physics tells us about the rules of connection within causal chains. It assumes those causal chains can determine patterns of experience but so far it has found no methodology for ascertaining the rules of correspondence immediately proximally between physical causation and experiential pattern. The first step in developing such a methodology must be working out what sort of proximal event we are dealing with.
Does A Gap Remain?
The arguments given above make the case for there being no reason to think that experience is unexpected in a physical world, if what we call physical is whatever has the power to influence experience. Nevertheless, there may be good reason to be puzzled, on a different basis. We may have good reason to be puzzled about a proximal correspondence between what appear to be nothing more than mathematical quantities in a handful of dimensions forming geometric patterns and things like emotions, truth, sensory modalities or a sense of identity and belonging.
Even this puzzlement may not be entirely fair. Although quantification of the causal nature of physical events is purely mathematical, as indicated earlier, the physical is something more than mathematical in that it involves the manifestation of mathematical possibilities as actual occurrences. However we portray causal relations, we need to bring in more than pure maths. We have to posit dynamic entities that might causally relate. Where there are relations there are possible concordances and discordances in patterns that could provide a basis for a concept of truth. Where there are individuals there are properties that belong to those individuals. Where there is sequence there is a good case for ‘becoming’ in some meaningful sense. The shift from possibility of an event to an occurrent event requires some sort of idea of necessity, or what Leibniz (1686) called reason, and it is not perhaps too big a jump to relate that to what is considered good or fitting and the possibility that some entity might ‘desire’ that fitting events should be actualized. The problem, of course, is that science has traditionally been agnostic about what fundamental entities such things might be attributed to.
Even bringing in these extra considerations about the physical that might mitigate the sense that it is just too austere to have any principled correspondence with subjective feelings, it remains hard to see how one might expect any correspondence to work in practice. There may be at least one reason why we should not be surprised by things to be obscure in this way; our experiences are mostly representations of events going on elsewhere. Almost everything in a human experience is vicarious. We might therefore expect values to be assigned in a way that does not correspond directly to what might seem likely equivalents in purely causal terms. The sense of disappointment that the ball is going to miss the net is coloured by which side kicked the ball. The usefulness of the evolved human mind almost certainly lies in ways of ‘borrowing’ from the repertoire of physical events to give rise to feelings to suit all sorts of concocted narratives that have evolved because they keep the whole human being alive.
In the final analysis, it would probably be hard to find anyone for whom there is absolutely no sense of perplexity about how the proximal correspondence between physical causation and phenomenal feel could work, even if we can argue that the perplexity is at least in part misguided. As for most other things in science what the correspondence rules turn out to be is going to be an empirical matter, and science has a habit of throwing up unexpected answers. An empirical answer is only going to emerge if we can pin down which proximal events are directly relevant to experience. For some time there has been a trend in neuroscience to shy away from this question but perhaps we are entering an era when it will be taken more seriously.
Aitchison, I.J.R. and Hey, A.J.G. (2004). Gauge Theories in Particle Physics. Taylor and Francis.
Alexander, S (2000) Dr Johnson as a Philosopher. In: Collected Works of Samuel Alexander Ed. Slater, J. Continuum Publishing Group (p119).
Chakravartty, A. (2017) Scientific Realism. Entry in Standford Encyclopedia of Philosophy. https://plato.stanford.edu/entries/scientific-realism/
Chalmers, D. (1997) The Conscious Mind. Oxford University Press.
Chomsky, N. (2000) New Horizons in the Study of language and Mind. Cambridge University Press.
Craddock TJA, Kurian P, Preto J, Sahu K, Hameroff SR, Klobukowski M, Tuszynski JA. (2017) Anesthetic Alterations of Collective Terahertz Oscillations in Tubulin Correlate with Clinical Potency: Implications for Anesthetic Action and Post-Operative Cognitive Dysfunction. Scientific Reports, 7(1):9877.
Davidson, D. (1970) Mental events. In L. Foster & J. W. Swanson (eds.), Essays on Actions and Events. Clarendon Press. pp. 207-224..
Dennett, D.C. (1991). Consciousness Explained. Penguin Books.
Eddington, A. (1927) The Nature of the Physical World. Kessinger Publishing.
Hubel, D.H. and Wiesel, T.N. (1959) Receptive fields of single neurones in the cat’s striate cortex. J Physiol, 148: 574-591
Hurley, S. (2006) The Varieties of Externalism. In: The Extended Mind, Ed. Menary, R. MIT Press.
Kant, I. (1781,2007) Critique of Pure Reason Translated by Weigelt, M. and Müller, M. Penguin Classics.
Leibniz, G.W. (1686) Discourse on Metaphysics. In G.W. Leibniz: Philosophical Texts. Translated by Woolhouse, R.S. and Francks, R. Oxford University Press.
Leibniz, G.W. (1714). Monadology. In Philosophical Works, G.W. Leibniz. Translated by Woolhouse, R.S. and Francks, R. Oxford University Press.
Levine, J. (1983) Materialism and qualia: the explanatory gap. Pacific Philosophical Quarterly 64: 354-61
Nagel, T. (1974) What is it like to be a bat? Philosophical Review 83; 435-50.
Noë, A. (2006). Action in Perception MIT Press.
Russell, B. (1927, 2007). The Analysis of Matte. Spokesman Books
Stoljar, D. (2006) Ignorance and Imagination: The Epistemic Origin of the Problem of Consciousness. Oxford: Oxford University Press.
Strawson, G. (2006) Consciousness and its Place in Nature: Does Physicalism Entail Panpsychism? Ed. Freeman, A. Imprint Academic.
Strawson, G. (2017) Consciousness never left. in The Return of Consciousness, ed. K. Almqvist and A. Haag. Axess Publishing AB.
 ‘It’s true that some twentieth-century philosophers and psychologists, crazed by theory, really did deny the existence of consciousness. Some danced in the behaviourist footsteps of Ryle and Wittgenstein (or rather, their versions of Ryle and Wittgenstein), holding that to be in intense pain is really just to behave in a certain way or be disposed to behave in a certain way. Some said that an orgasm is really just a “sentence in the head” with no sort of conscious feel to it at all.’ (Strawson, 2017)