How qualia can be physical


Dennis Nicholson




A small shift in how qualia are viewed can yield significant gains for physicalism.


What we have immediately available to us as external observers of brain states cannot be the physical realities of those states ‘in the raw’. The physical states themselves and the senses we perceive them through are physically separate things, so what we see and otherwise sense when observing (say) electrochemical activity in a particular group of solid-seeming neurons can only be a sensory impression, physically separate from the thing itself. It is not the actual physical state, which is part of another organism, but an external observer’s experiential perspective on the actual physical state – the reality as known as distinct from the reality as such.


Take it that a quale[1] such as a blue flash or a tinkling sound is an internal observer’s experiential perspective on an underlying physical state – that it, too, is the reality as known as distinct from the reality as such. Take it that, in this case, the experiential perspective is integral to, and materially co-extensive with, the physical state[2] itself; that the quale, perspective included, is really nothing over and above that physical state – an entirely physical thing. Take it, finally, that the physical state in question is known to an external observer as a particular kind of brain state. The position, I shall show, is a useful one. It dispels the notion of an unbridgeable mental-physical gap, resolves difficulties for physicalism associated with Leibniz’s Law, Jackson’s knowledge argument, and Chalmers’ hard problem of consciousness, and provides in the process a possible basis for a scientific account of human experience.


Bridging the gap; Leibniz’s Law


If we assume, contrary to the above, that the quale we experience is a reality ‘in the raw’ rather than a perspective on a reality, and that the same is true of the brain state we experience, the two appear fundamentally different. We find it hard to see how we can fit what we tend to think of as the insubstantial-seeming mental world of qualia into what we tend to think of as the solid-seeming physical world of the fleshy, material brain. Qualia – experiences like blue flashes and tinkling sounds – appear so very different to solid bundles of electrochemically-active neurons that we find it close to impossible to envisage either how a quale and a brain state can be the same thing, or how the two can causally interact. There is an apparently unbridgeable gap between the mental and the physical.  With McGinn (1989), we cannot readily envisage how ‘technicolour phenomenology’ can arise from ‘soggy grey matter’ – or, indeed, how the former can causally influence the latter. These difficulties fall away, however, if we reject this two realities position in favour of the two perspectives position outlined above.  We no longer have two realities too different to be one thing, or be causally related, but two very different perspectives on a single physical state whose underlying cause is the physical state itself.


In this position, there is no barrier to a brain state and a quale being a single physical state. The fact that they each appear too different to be the same thing is not a problem. The differences are in our perspectives (the reality as known), not in the underlying reality (the reality ‘in the raw’). Nor is there a need to explain how a brain state (an external observer’s experience of a physical state in another organism) gives rise to a quale (the other organism’s own experience of it). An experience in one organism cannot reasonably be thought to cause an experience in another. In the two perspectives position, the need is to explain what it is about the underlying physical state that causes one observer to experience it as neuronal electrochemical activity and another to experience it as blueness, or a tinkling sound. We must account for two very different sets of observed characteristics in terms of the physical state that is the underlying cause of each, rather than explain how one set gives rise to the other. The unbridgeable gap disappears[3], replaced by a form of identity theory[4] consistent with Leibniz’s Law.


Leibniz’s Law states that if x is (identical with) y, then any property of x is a property of y. This is a difficulty if we begin from the perspective of the two realities position, for a quale and a brain state are then so unalike that it is hard to see how they could possibly be one thing with a single common set of properties. The difficulty disappears if the two perspectives position is adopted, however. The fact that it is true of a quale that it is non-extended, non-solid, non-located in space, private, and is ‘like’ something (pain, for example) – and that a brain state is none of these things (cf Himma 2005:83) - is not a problem in this position. If, as is claimed, the inner (quale) perspective is integral to, and materially co-extensive with, a physical state known to an external observer as a brain state, we have a single reality with one set of properties. As a physical state underlying a brain state, the reality is a publicly-observable, material, spatially-locatable, physical thing with a discoverable functional role (a tendency to avoid, say). As a state that, physically, wholly encompasses the inner perspective, it is also a privately-observable sensation (pain, say). Contradictions fall away, attributable to limitations in the perspectives. If it is private and painful in one perspective and public and spatially-locatable in the other then, as required by the Law, it is all of these. Earlier identity theories associated with Place, Smart and others had to combat claims of conflict with Leibniz’s Law in just these areas[5], but the two perspectives position is entirely compatible with it. There is one reality with a single set of properties at the heart of the identity claim – a reality that, physically, wholly subsumes experience, bringing it entirely within the bounds of scientific investigation.


Jackson’s knowledge argument refuted


The position is also able to counter Jackson’s knowledge argument, the best known form of which is the 'grey Mary' thought experiment (Jackson 1982, 1986). Mary lives in a black and white room and acquires all of the physical information there is to obtain about the world and all of our visual experiences of it through a black and white television. She must be able to do this, claims Jackson, otherwise the Open University would, of necessity, need to use colour television. However, it seems ‘just obvious’ that Mary will learn something new on leaving the room – she will learn what colours like red or blue are really like. But she had all of the physical information already, so this new information – knowledge of qualia - must be non-physical information. Physicalism – the idea that the world comprises only physical things – is false.


The argument has inspired significant debate over the years[6], and continues to do so [7] despite Jackson’s own recent conversion (Jackson 2003), but its claims are refuted if the two perspectives position is true. If our inner experiences are, as this proposes, perspectives on physical states that are integral to, and materially co-extensive with, the physical states themselves, two things follow. First, that they are knowledge of something physical - experiential physical knowledge (cf. Deutsch 1999); second, that they are perspectives that are themselves (made of) something physical. If the two perspectives position is true – and it is, I submit, a coherent position with a reasonable chance of being correct – the knowledge Mary acquires on leaving her room is physical knowledge that is itself physical; it cannot reasonably be held to refute physicalism. Of course, it, like the knowledge argument, is only a thought experiment. We cannot say that either is true; only that each is plausible. But a plausible thought experiment that shows how physicalism can be true seriously undermines one that supports the conclusion that physicalism must be false. Not only is a contrary case presented, effectively refuting the knowledge argument by showing how physicalism can plausibly be true, but the basis of the argument itself is called into question. If physicalism can be true – and the two perspectives position shows that it can – then an argument that supports the conclusion that it must be false, must be flawed.


Obvious questions arise. Where is the flaw? Why does the argument appear plausible regardless? But the two perspectives position has answers. If it is true, Jackson’s first premise (that Mary acquires all the physical knowledge in her room) can be false, yet appear true. ‘Base feels’ (blue, or tinkling, or hot – the qualities that distinguish qualia from each other), and ‘baseline experience’ (experience itself - the quality they have in common) are really nothing but something physical in this position. We can expect that each of these elements of the inner perspective will have externally observable counterparts[8] able to be identified, labelled and studied by an external observer employing the same scientific methods used to study all other physical things. More, since the associated elements of inner experience ‘just are’ these externally observable counterparts, it should be possible to discover, express, and acquire as complete an account of the physical states that are qualia as we can of any other physical thing we study based only on these externally observable counterparts.


If Mary can acquire such an account in her black and white room – and by Jackson’s lights she can – she will have a close-to-comprehensive scientific account of human experience. She will have knowledge of qualia sufficient to fulfil any manipulative or explanatory purpose evident to an external observer – even to the extent of being able to bring about the occurrence of a given physical state that is a quale, inner perspective and all. It will thus appear possible for the Open University to impart all of the physical knowledge about qualia to Mary. Mary will end up with as complete a knowledge of the physical states that are qualia as she can have of any other thing studied by science. From the two perspectives position, however, she will still have something physical to learn. Jackson’s first premise – and, hence, his conclusion – will be false.


Of course, Jackson himself now argues (Jackson 2003:14-26), in defence of his own conversion to physicalism, that Mary acquires no new knowledge, only a new found ability to represent knowledge she already had in a new way. Two points are worth making about this. First, in the two perspectives position, such a defence is unnecessary – Mary’s new knowledge being no threat to physicalism in this view. Second, it does not seem to be true that she learns nothing new. Mary may well acquire an ability to represent knowledge she already had in a new way, but she still seems to acquire additional knowledge content – new knowledge – by learning what the physical states that occur in herself and others exercising this ability are like[9]. Before, she may have known the knowledge content now represented as blueness, but she did not know blueness itself[10]. She could not have done. The knowledge content that is expressed as blueness, redness, and so on cannot be acquired by someone in Mary’s circumstances. It cannot be expressed or acquired verbally or via diagrams or models, and any attempt to provide illustrative examples will fail; Mary will see only greyscale versions.  The Open University will be able to give Mary accurate accounts of qualia sufficient for most purposes – physical control, intelligent discussion, even explanatory understanding up to a point. However, she will still have something to learn – something key to the resolution of Chalmers’ hard problem of consciousness and to the provision of a scientific account of human experience.


The hard problem resolved


For Chalmers (Chalmers 1995, 1996, 2003) the problem of consciousness – the problem of explaining why blueness or redness is like it is or, indeed, why experience exists at all (why it is ‘like’ anything) - is (almost) uniquely hard. So much so, that we must take experience itself as a fundamental property of the world alongside mass, charge, and space-time to encompass it in our world-view. From the perspective of the two realities position on qualia, Chalmers is right on both counts[11]. In this, mental things like blueness or redness and baseline experience appear so different to physical things like brain states or elements of brain states that we cannot see, either how they can be reducible to such physical things, or how they can be causally related to them. The problem of explaining the experiential in terms of the physical is uniquely hard because there is an apparently unbridgeable gap between the two. This is a significant difficulty if we wish to make experience part of a physicalist world view. An account of human sensory systems in what we regard as purely physical terms in this perspective leaves experience out of the physicalist equation entirely. Since the experiential appears to sit outside of the physical continuum, and to be irreducible to it, we cannot claim of such an account that it explains experience, nor even includes it. It does not deal with it in any way. If we wish to relate experience to the physical in this view, then, like Chalmers, we must ‘add’ experience to our physicalist world-view and create a new synthesis. And since the experiential is apparently so utterly different that the physical we know cannot account for it, taking experience itself as an additional fundamental property of the world alongside mass, charge, and space-time appears to be the best option.


In the two perspectives position this move is unnecessary. The problem of consciousness can be solved by taking the relatively trivial step of mapping the internal observer’s experiential knowledge of baseline experience and the various base feels into a complete account of the physical detail of their externally observable counterparts. There is no hard problem in this view; no unbridgeable gap. Experience does not sit outside of the physical continuum as presently understood in some irreducibly disconnected fashion. Physically, the elements of inner experience are integral to, and materially co-extensive with, their externally observable counterparts; they are one and the same thing. Not only is a complete account of the physical detail of these externally observable counterparts as complete an account of these aspects of the physical states that are qualia as we can have of any other physical thing we study, it is an account that encompasses the whole of the (physical) reality of the inner experiences they entail. The only thing missing from such an account is the knowledge content unique to the inner experiences themselves – knowledge of what blue and red and experience itself are like – everything else is encompassed in what would otherwise be a complete physical account of the whole physical thing. And since these elements of the inner perspective are experiential physical knowledge in this position, they can be mapped into the otherwise complete physical account of their externally observable counterparts as experiential physical knowledge; knowledge that, physically, is itself really nothing over and above these counterparts, and so, can be accounted for in terms of their physical detail. The hard problem is resolved – without the need to challenge physicists’ views on the fundamental properties of the world.


It may seem on first consideration that this does not provide a physical account of the elements of inner experience; that it merely adds experiential knowledge of these elements to a physical account of their externally observable counterparts. In fact, this is all that is required. In this perspective, the elements of inner experience and their externally observed counterparts are one and the same thing, experienced differently. We can consider them different ways of knowing – of representing and labelling – the same physical reality. They are, if you like, the same problem in different guises, and have, perforce, the same solution; one that is to be found in a complete account of the physical detail discoverable by studying them externally. The whole of the physical reality of the internal observer’s ‘guise’ is encompassed and explained by such an account, only the knowledge of what this guise is like to an internal observer is omitted. A full account of the physical detail of the externally observed counterpart of baseline experience should, for example, be able to encompass and explain the fact that qualia are ‘like something internally’ and even the fact that this something is like what it is like and not like something else. The only fact about this aspect of qualia it cannot encompass is the (experiential) fact of what it is like internally – an omission readily resolved by mapping it into the otherwise complete external observer’s account as experiential physical knowledge.


This experiential knowledge is trivial in operational and content terms, but in this perspective a physical account of qualia is incomplete and misleading without it. Experienced blueness is irrelevant to a physical account of a blue cube; it expresses a fact about how humans experience the cube, not about the cube itself. In the two perspectives position, however, experienced blueness is integral to – really nothing over and above - the physical state that is the blue quale. This means that it is characteristic of the physical state itself. Experienced blueness is, if you like, something the physical state does – something intrinsic, the facts about which must be encompassed in any complete view. 


But the facts in question – what blueness and baseline experience are like – can only be expressed and encompassed as experiences. Unless we include baseline experience in our account, we leave out the essential characteristic of a physical state that is a quale, the thing that best distinguishes it from other physical states – experience itself. Even a verbal recognition that the state is ‘like something internally’ fails to encompass the character, extent, and significant nature of the difference between a blue quale and something inert like sand; only the actual experience can fully express and encompass the fact in question. The same applies to the blue character of the quale – only actual experienced blueness fully captures what characterises this quale and distinguishes it from all others; neither words, nor externally observed counterparts encompass the fact in question. Unless we map these actual experiences into our account, it will be incomplete and misleading. Incomplete because, facts about key – even defining – characteristics will be missing. Misleading because it will appear that the physical things we are describing and explaining do not have these inner experiential characteristics; that they only have those observed externally.


A possible basis for a scientific account of human experience


With these experiential elements in place, however, we have, on the face of it, an account that not only resolves the hard problem but also provides a possible basis for a scientific account of human experience. In this perspective, the problem of consciousness – of human experience – is a physical world problem like any other, able to be dealt with in essentially the same fashion. Questions such as why is blue like it is and why does experience exist at all (why is there an ‘inner perspective’ – why is it ‘like’ anything) are no more difficult than any others tackled by science. They can be dealt with by mapping the experiences themselves to the externally observed attribute of the physical state present when they are present and absent otherwise, then accounting for any given experiential characteristic in terms of the detail of the scientifically discovered differences between the physical states that have the attribute and others that do not. A quale will be blue because it differs in discoverable (physical) ways from a red quale, say, or a tinkling sound quale. Experience itself (baseline experience) will be ‘like anything’ because it differs in discoverable physical ways to physical states in the organism and elsewhere that do not exhibit this characteristic. In each case, we will discover the account through the scientific study of the physical state itself. The only barrier to regarding this as the basis of a scientific account would appear to be the need to include experience itself in the account.


Whether this is a problem or not will require deeper consideration than is possible here. Arguably, however, adding experience in this way is not only both necessary and scientifically justifiable (the account is incomplete and misleading without it), it is also innocuous (the information is non-verbal and cannot add to or contradict the assertions entailed in the external observer’s view). In consequence, it is, I submit, reasonable to suggest that the two perspectives position offers a possible basis for a scientific account of human experience.



Alter, T. 2006. The Knowledge Argument. Forthcoming in Blackwell Companion to Consciousness, eds. Schneider, S. And Velmans, M. Available at Knowledge Argument.pdf

Borst, C.V. 1970. The Mind-Brain IdentityTheory. London: MacMillan.

Chalmers, D. J. 1995. Facing up to the problem of consciousness. Journal of Consciousness Studies, 2(3):200-219

Chalmers, D. J. 1996. The Conscious Mind. New York and Oxford: Oxford University Press.

Chalmers, D.J. 2003. Consciousness and its Place in Nature. In Blackwell Guide to the Philosophy of Mind, eds. Stich, S and Warfield, F. Oxford: Blackwell

Deutsch, M. 1999. Subjective Physical Facts. Paper given at conference on The Conscious Mind, University of Buffalo, 1999. Available at

Himma, K.E. 2005. What is a Problem for All is a Problem for None: Substance Dualism, Physicalism, and the Mind-Body Problem. American Philosophical Quarterly. 42(2):81-92.

Horowitz, A. and Jacobson-Horowitz, H. 2005. The Knowledge argument And Higher-Order Properties. Ratio. XVIII:48-64.

Jackson, F. 1982. Epiphenomenal Qualia. Philosophical Quarterly. 32:127-36.

Jackson, F. 1986. What Mary Didn't Know. The Journal of Philosophy. 83:291-95.

Jackson, F. 2003. Mind and Illusion. In Minds and Persons, ed. O’Hear, A. 251-271.Cambridge: Cambridge University Press.

McGinn, C. 1989. Can We Solve the Mind-Body Problem, Mind, 98, 891:349-366.

Papineau, D. 1993. Physicalism, Consciousness, and the Antipathetic Fallacy. Australasian Journal of Philosophy. 71(2):169-182.

Shoemeaker, S. 1999. (and following papers) On David Chalmers’s The Conscious Mind. Philosophy and Phenomenological Research. LIX(2):439-472.

Strawson, G. 1994. Mental Reality. Cambridge, Mass: the MIT Press, Bradford Books.

Tye, M. 1999. Phenomenal Consciousness: The Explanatory Gap As A Cognitive Illusion. Mind. 108, 432: 705-725.

[1] Sensory states are my focus here, but I take qualia to include all mental states, including (with Strawson 1994) thoughts.

[2] One ‘state’, but encompassing further physical detail

[3]Its existence has, of course, been challenged by others - see e.g. Papineau 1993, Tye 1999.

[4] The position is compatible with token identity, but type identity seems the better ‘fit’. Anti-type arguments based on multiple-realizability (Putnam, 1967) seem to me to be challengeable. A quale-type could have a common basis at some physical level, yet still occur in different organismic contexts (experienced blue in two people, pain in different species).  Indeed, experiential (as opposed to just functional) identity might arguably require it.

[5] Borst, 1970 is illustrative and has the original papers

[6] Alter 2006 has a useful summary.

[7] See, for example, Horowitz and Jacobson-Horowitz 2005.

[8] Again, these may encompass further physical detail.

[9] In Jackson’s terms (2003: 26) they (the physical states) are the referent of the demonstrative.

[10] Chalmers 1996: 144-45 makes the same point in response to the ability arguments of Lewis and Nemirow

[11] My aim here is not to counter Chalmers’ arguments as such; only to show that, whilst these two particular conclusions seem an inevitable consequence of the two realities position, neither holds true under the two perspectives position. That said, it is worth noting that Chalmers bases a significant part of his case (cf. Shoemaker 1999 and following papers) on the idea that zombies, physically identical to us but lacking inner experiences, are possible – claiming, in essence, that, since zombies are possible, reductionalist physicalism must be false. My counter to this is that, since the two perspectives position shows that zombies can be impossible - that there is a possible world in which our physical make-up necessarily entails having inner experiences - reductionalist physicalism can be true.