Solving the Mind-Body Problem - The Real Significance of the Knowledge Argument

1 Introduction

In this paper, I examine Frank Jackson�s famous 'grey Mary' thought experiment, first presented in "Epiphenomenal Qualia" (Jackson 1982) in support of his Knowledge Argument against physicalism. I argue that its real significance is not that it shows that physicalism must be false, but that it shows what must be true of the nature of qualia and their relationship to the physical if physicalism is true. In the process, I further suggest that Jackson is mistaken in claiming, in a more recent paper (Jackson, 1998), that his original Knowledge Argument was flawed because it was based on a "false intuition'. In my view, the real flaw lies in formulating the Knowledge Argument in a way that predetermines the outcome in favour of a refutation of physicalism. If we reformulate it so as to remove this flaw, it becomes clear, not only that physicalism can survive Jackson's thought experiment, but also that there is only one view of the relationship between qualia and the physical (between 'mind' and 'body') that will permit it to do so. The point being that, if physicalism is true, this one view of the relationship between qualia and the physical must then be the correct view - the solution to the mind-body problem. Independent support for this conclusion - support from sources other than the Knowledge Argument - is also provided. The perspective on the relationship required to enable physicalism to survive the reformulated knowledge argument is a form of identity theory consistent with Leibniz's Law and appears to resolve the problems posed by:

� Kripke's problem for proposed identities (Kripke, 1980)

� McGinn's assertion that 'We cannot conceive of how technicolor phenomenology can arise from soggy grey matter' (McGinn, 1989)

� Chalmers' 'hard problem' of consciousness (Chalmers 1995)

1 Jackson's Knowledge Argument

1.1 The Argument

This is how Jackson first set out his Knowledge Argument against physicalism in terms of what is sometimes called the 'grey Mary' thought experiment:

Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specializes in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like �red�, �blue�, and so on. She discovers, for example, just which wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal chords and expulsion of air from the lungs that results in the uttering of the sentence �The sky is blue�. (It can hardly be denied that it is in principle possible to obtain all this physical information from black and white television, otherwise the Open University would of necessity need to use color television.)

What will happen when Mary is released from her black and white room or is given a color television monitor? Will she learn anything or not? It seems just obvious that she will learn something about the world and our visual experience of it. But then it is inescapable that her previous knowledge was incomplete. But she had all the physical information. Ergo there is more to have than that, and Physicalism is false.

(Jackson, 1982)

On the face of it, the case is a persuasive one. If physicalism is true, then physical facts are the only facts - but if Mary learns all of the physical facts about colour vision in her black and white room and still learns something new on leaving it, she has acquired a fact that is not a physical fact and physicalism cannot be true. The logic is sound If the premises are both true - if, following Jackson 1986, it is true:

[Premise A] that Mary (before her release) knows everything physical there is to know about other people.

[Premise B] that Mary (before her release) does not know everything there is to know about other people (because she learns something about them on her release).

Then the conclusion that physicalism is refuted is inescapable.

Whether the conclusion is correct is, of course, another matter, and it is true to say that there is a fair degree of dispute on the point. What is less in dispute is that Jackson's argument presents a challenge to physicalism that cannot easily be ignored or discounted. A steady stream of responses for and against it has appeared in the literature since its initial airing in 1982, and the activity shows no sign of ceasing. Since the conclusion that physicalism is refuted follows inevitably if the premises are both true, these responses necessarily take the form of challenges to one or other or both of the premises from those who seek to defend physicalism, and of counter challenges from those who seek, either to challenge physicalism or to challenge the arguments put in its defence.

Much of the literature to date reflects a continuing debate on challenges to premise B and shows that the issue of their efficacy (or otherwise) is still in dispute after many years of discussion. This literature is of interest here for two reasons. First, because it helps illustrate the nature of the difficulties that the Knowledge Argument creates for physicalism; second, because the evidence of continuing dispute arguably provides some indirect support for the position taken in the present paper, which is that challenges to premise B are misdirected and unnecessary - because the real problem lies with premise A.

2 Challenging Premise B

The major positions taken against premise B in the literature are these:

Physicalism stands because, contrary to our intuition, Mary learns nothing new on leaving the room 2.2.1

This is a position most often associated with Dennett, (1991, 398-401), but a similar point is put by Churchland (1985, 25-28). To put it in terms of Dennett�s account, we only believe that Mary learns something new on leaving her black and white room because we underestimate how much the pre-release Mary already knew. According to this view, if Mary really knows as much as is supposed by the Knowledge Argument, she will already be capable of identifying the colours she is about to experience by making inferences from observations of the physical states they induce. While this may be true, it is not pertinent. The problem with the position is that being able to identify a colour by this means is not the same as knowing what the colour is like. Mary may be able to identify colours such as red before her release based on physical states, but she will not know what they are like and will therefore still learn something new when she leaves � a counter position put by Robinson (1993) and Alter (1998) amongst others.

2.2.2 Physicalism stands because what Mary learns is not a fact, but something else such as know-how or ability.

Numerous objections to the ability hypothesis have been raised in the literature (see, for example, Alter 1998, 2000, Conee 1994, Deutsch 1998, Gertler 1999, and Loar 1990), but the following points are sufficient to illustrate the continuing dispute over it:

i. Mary seems to gain more than an ability when she experiences red for the first time. As Chalmers 1996 points out, the idea that, when she first experiences red, Mary learns nothing more than a new ability is not plausible. Mary probably does gain a new ability when she first experiences red (e.g. the ability to recognise experienced red). However, she also seems to acquire knowledge of what red as experienced is like. 'For all she knew before, the experience of red things might have been like this, or it might have been like that, or it might have been like nothing at all. But now she knows it is like this'. Conee 1994 makes a similar point, arguing that knowing how to visualise a colour is not sufficient for knowing what it is like to actually see it. He also makes the further point that it is possible to be able to experience what a red tomato is like in the here and now, yet have no ability to imagine, remember and recognise the experience before or after. For Conee, having an ability is neither necessary nor sufficient for knowing what it is like to have such an experience (a position also taken by others - see, for example, Gertler 1999).

ii. Acquiring a new ability such as driving a car or swimming usually also entails acquiring factual knowledge - knowledge of what it feels like when one does these things. An exception arises out of the idea put in Dennett 1991 suggesting that Mary could identify a colour on first seeing it simply by recognising that its physical effects were occurring in herself. This, however, does not help supporters of the ability hypothesis. It seems clear that Mary might, by this means, already possess the ability to recognise red before leaving the room, yet would still learn a new fact on experiencing red for the first time. She would learn that there is more to seeing red in humans than the occurrence of physical states; that seeing red in humans is also like 'this'.

iii. Lycan lists nine criticisms of the ability hypothesis in Lycan 1995 and ten in Lycan 1996 arguing, amongst other things, that:

� Knowing what it is like to have an experience is arguably to know that it is like such and such to have that experience - so it is knowing a fact, rather than having an ability.

� The best explanation of our imaginative and other abilities in respect of visualising red or blue is the possession of factual knowledge of what it is like to see these colours.

� Since one can try to describe an experience such as the taste of pineapple to someone, even if we would probably fail, it would appear that knowing what it is like means having some fact to impart.

Conee 1994 offers an alternative �not a new fact� position, arguing that Mary acquires only acquaintance knowledge and that this neither implies nor excludes physicalism. This position is accepted in the present paper, although a different perspective is taken on the implications.

2.2.3 Physicalism stands because what Mary learns is not a new fact only an old fact in a new guise.

Another much favoured position taken by a range of writers (Horgan 1984, Churchland 1985, Loar 1990, Lycan 1995, Papineau 1993, Tye 1986 are examples, others are referenced in Nida-R�melin 2002, Vinueza n.d., Alter n.d., and Chalmers 1996) is the so-called old fact/new guise argument. This is the view that the Knowledge Argument does not refute physicalism because what Mary comes to know when she leaves her black and white room is not a new fact, just a fact she already knew known or represented in a new way. At its simplest, the case is based around examples (water and H2O, Clark Kent and Superman, Mark Twain and Samuel Clemens, temperature and mean kinetic energy) where two different labels actually denote the same thing (but indicate different properties). Whilst a fact like "The morning star is the planet Venus" arguably expresses the same fact as "The evening star is the planet Venus", one can be known without the other being known. It is possible, therefore, that whilst Mary appears to learn a new fact when leaving the black and white room, she really only learns a fact she already knew under a new guise. Physicalism is not refuted because, despite appearances, Mary has not really learned a new fact.

The old fact/new guise argument, in a variety of forms, is a widely held position amongst those challenging premise B. However, at least two telling objections to it have been raised:

i. First, as Chalmers 1996 points out, the problem with the approach is that "Whenever one knows a fact under one mode of presentation but not under another, there will always be a different fact that one lacks knowledge of". The fact that "The evening star is the planet Venus" may only be the fact that "The morning star is the planet Venus" in a new guise, but to learn that both statements express the same fact is to learn something new. It is to learn that the morning star and the evening star are the same thing, or that Venus has an additional, previously unknown, characteristic. By analogy, even if it is true that Mary, on leaving her black and white room, has simply learned that experience X is seeing red and brain event Y is seeing red, she has still learned something new. She has learned that there is more to be known about seeing red than is known when it is known about in terms of brain event Y. Thus it is still the case that she has learned something new. If it is true, as claimed in Jackson's thought experiment, that she already knew all of the physical facts in her black and white room, then her new knowledge must still refute physicalism. If it is not - and this, as will become clear presently, is perhaps more interesting, then physicalism may or may not be refuted, depending upon whether or not we can regard Mary's new knowledge as being, in some sense, a physical fact.

ii. Second, as Alter 1998 argues, the idea that all that Mary has acquired is an old fact in a new phenomenal guise seems to suggest that the new phenomenal guise (experienced red as opposed to its neurological correlates, for example) is incidental to knowing the fact in question. This, however, seems improbable at best. In the case of qualities such as experienced red, knowing the �phenomenal guise� � the actual experience � appears central to the fact itself. We cannot know experienced red � the fact itself � without knowing the �phenomenal guise�. And since the �phenomenal guise� (experienced red) cannot be known in a black and white room, it cannot be an old fact, it must be a new one. The threat to physicalism stands. An analogy (provided by Alter) would be the suggestion that one could know that the boxer called Ali had once been called Clay without first having acquired the label �Clay�.

A variation on the old fact/new guise position, primarily associated with Bigelow and Pargetter (1990), argues that what Mary acquires is similar to indexical knowledge. Mary, it is suggested, is like the absent-minded historian who knows all the objective facts but can still learn that today is July 4th, American Independence day. She knows all of the objective facts about colour vision but can still learn that this (experienced red) is red. The point being that, since indexical knowledge does not refute physicalism, we have no grounds for holding that Mary�s new knowledge does either. The problem with this view is, as Chalmers 1996 points out, giving Mary perfect knowledge about her indexical relationship to everything in the physical world would not improve her knowledge of red experiences one bit.

I do not contend that challenges to premise B must fail, or even that they have to date. Proving this would require a far more exhaustive examination of the literature on premise B than I have been able to present here, and may, in any case, be impossible. My one claim here in respect of such challenges is that they are misdirected and unnecessary � simply because the real problem lies with premise A, a point I shall develop below. This having been said, it should be clear from the above summary that those who challenge premise B face significant difficulties in making a secure case. There is a good deal of evidence to suggest that coherent counter positions can be put, that there is a continuing dispute as to the efficacy of such challenges, and that neither side has yet convinced the other of its case. Enough, at any rate, to suggest that the alternative approach taken in the present paper is at least worth examining.

It might be possible for supporters of premise B challenges to make something of the fact that Jackson himself has latterly suggested (Jackson 1998) that premise B is false, were it not for the fact that, as Vinueza n.d. notes, Jackson does not really present a case, only indicates his feeling that there must be one. In any case, if I understand him correctly, he is approaching the problem from the following angle:

� Physicalism must be true;

� The Knowledge Argument is valid, so physicalism must be false unless our intuition is false;

� Therefore, the puzzle is to explain why we are mistaken in our intuition.

If this is so, he may well be willing to concede that the solution to the conundrum of the Knowledge Argument proposed in the present paper offers a better alternative, despite the fact that it entails an assumption that Mary does acquire new knowledge. Certainly, his own suggestion as to why our intuition might be mistaken does not convince. This is that Mary's knowledge is not new, but could be arrived at by following a long and complex chain of inference. Our intuition that it is new is an illusion created by the fact that it is acquired in a much more immediate 'all at once' fashion (a position, interestingly enough, that seems rather similar to Dennett�s (1991)).

3 Challenging Premise A

As previously indicated, the position proposed in the present paper draws the debate away from premise B. Focusing instead on premise A, it offers a solution that shares common ground, in varying degrees, with positions taken by writers such as:

� Flanagan 1992, who exposes essentially the same problem with premise A identified in the present paper, albeit in a different fashion, and also reaches a similar conclusion as regards Mary's new knowledge - that it can be physical and a way of knowing the physical world without being fully expressible in the language of even a completed science.

� Conee 1994, who argues that Mary�s new knowledge is only acquaintance knowledge, not prepositional knowledge, and that there is no case for believing that acquiring such knowledge represents a challenge to physicalism � that acquaintance knowledge may just be knowledge of something physical that Mary already has prepositional knowledge of and that does not encompass any new (prepositional) fact.

� Alter 1998, who defends the Knowledge Argument, but argues that it need not necessarily refute physicalism, noting that Mary�s experiences might well be physical events that cannot be learned by discursive means, and that physicalism can survive the Knowledge Argument if we accept the idea that some facts are not discursively learnable and simply reject physicalist perspectives that assume otherwise.

� Deutsch 1998, who argues that the Knowledge Argument does refute physicalism if we adopt what he calls the language of science conception of physical facts but not if we adopt an ontological conception of the physical facts, and that the first of these is harmless and only tells us that the language of science cannot handle subjective physical facts.

� Sommers 2002, who argues (albeit on different grounds than I do) that we assume too much when we accept premise A.

Echoes of all of the above positions are to be found in what follows, although the position put is, I think, entirely new. In essence, I argue that premise A is formulated in such a way as to predetermine the outcome of the thought experiment in favour of a refutation of physicalism. If it is reformulated so as to remove this flaw, then there are circumstances in which Mary's acquisition of new knowledge on leaving her black and white room will not refute physicalism.

3. What Mary Might Think of the Knowledge Argument

I shall begin my attempt to describe, develop and defend this position by considering the possibility that Mary herself could have reason to think that there is a problem with Jackson's Knowledge Argument. Note, first of all, that it is possible - and entirely consistent with Jackson's thought experiment - that Mary should expect to learn something new on leaving her black and white room. Lets suppose that both she and the physicalists outside of her room have equipment that allows them to know the physical process of seeing as observed by an external or outside observer of the human organism down to the very last detail. By using this equipment, Mary is able to compare an outside observer�s perspective on what goes on physically in humans living outside her room when they see a red tomato with an outside observer�s perspective on what goes on physically in herself when she sees it on her black and white screen. Since Mary presumably sees a shade of grey for 'red', it is entirely possible (if physicalism is true) that an outside observer�s detailed description of the physical processes that take place in humans outside Mary's room seeing red will differ slightly from a similar description of those that take place in Mary when she sees her shade of grey. In short, it is possible that the experiential differences created by Mary's black and white room are reflected in Mary�s physical processes as observed by an outside observer.

If Mary notices such differences between herself and other humans when seeing �red�, it is entirely possible that she will expect to learn something new when she leaves her black and white room. Since she does have experiences - albeit black and white ones - she may even suspect from what she hears of 'red' from the outside world that the physical differences between herself seeing red and outside world people seeing red have a phenomenological correlate, and that the new knowledge she expects will be experiential. If so, she may be fascinated, even startled, by what she learns about red when she leaves her black and white room, but she will not be surprised to learn this new thing. Nor will she be surprised if she then finds that the physical differences spotted earlier between herself when she saw 'red' as a shade of grey and others in the outside world seeing red for real are no longer in evidence. In fact, she might well conclude on making such an observation, that, since the appearance and disappearance of her new experiential knowledge seems to be accompanied by the appearance and disappearance of a particular physical state, it shows every sign of being something that is:

� Simply another way of knowing something physical;

� Physical itself.

.

If so, she is likely to be surprised to find that supporters of the Knowledge Argument regard her new knowledge as evidence that physicalism - the doctrine that the world is entirely physical and that all facts are physical facts - is false. On hearing that this view is based on the assumption that she was able to acquire all physical knowledge of colour vision inside her black and white room, it is likely that she will suspect:

� That there is a problem with the Knowledge Argument (since it forces the conclusion that her new knowledge must refute physicalism but her observations suggest otherwise).

� That the focus of this problem is the assertion that it is possible for someone in a black and white room to acquire all physical knowledge (since it is this premise that defines her newly acquired knowledge in such a way that it must refute physicalism)

If so, she will, in my view, be correct on both counts.

4. The Flaw in the Knowledge Argument

There is a flaw in the Knowledge Argument as stated (following Jackson) in section 2 above. It is undeniably true that if Mary acquires a complete physical knowledge of colour vision inside her black and white room, then her acquisition of new knowledge on leaving that room must refute physicalism, simply because it is new. If all physical knowledge relevant to colour vision has already been acquired inside Mary's black and white room, then any new knowledge acquired on leaving it can only be knowledge of something non-physical and must, perforce, refute physicalism. If it is accepted that Mary acquires all physical knowledge of colour vision in her black and white room therefore, the knowledge Mary acquires on leaving her black and white room necessarily refutes physicalism simply because it is new knowledge.

However, it is not true that knowledge acquired by Mary on leaving her black and white room will necessarily refute physicalism simply by virtue of being new. There are at least three sets of circumstances in which we would not be justified in drawing this conclusion:

4.1 If, as in the extended Mary example described in section 3 above, Mary's new knowledge is valid knowledge of the physical and is itself ("made of" something) physical, then it cannot reasonably be held to refute physicalism, regardless of whether or not it is new.

4.2 If Mary made no attempt to acquire a complete physical knowledge of colour vision in her black and white room, and so left it without having acquired complete physical knowledge, then we could not justifiably conclude that any knowledge she acquired on leaving her black and white room refuted physicalism simply because it was new. Since in this set of circumstances her physical knowledge of colour vision is incomplete when she leaves the room, the fact that any knowledge she acquires afterwards is new does not preclude the possibility that it is physical knowledge. In these circumstances, therefore, we can only justifiably conclude that physicalism is refuted by any new knowledge that Mary acquires on leaving her black and white room on the basis of the nature of the new knowledge itself. If it is valid knowledge of something non-physical or non-physical itself, then it can be held to refute physicalism; if it is valid knowledge of the physical that is itself physical as in the example in section 3, then it cannot reasonably be held to refute physicalism. The question of whether or not it is new is, in these circumstances, irrelevant - it proves nothing one way or another about physicalism.

4.3 If we left the question of whether or not Mary could acquire a complete physical knowledge of colour vision inside her black and white room open, neither assuming that she could, nor that she could not, then we could not justifiably conclude that new knowledge acquired on leaving her black and white room refuted physicalism simply because it was new. In these circumstances, it remains possible that the knowledge acquired on leaving the room is new simply because it is knowledge that could not be acquired inside the black and white room. Once again, therefore, the question of whether or not it refuted physicalism would depend, not upon its newness, but upon the nature of the new knowledge itself. If it was valid knowledge of something non-physical, or non-physical itself, or both, then it could be held to refute physicalism. If, on the other hand, it was valid knowledge of the physical that was itself physical, then it could not reasonably be held to refute physicalism, regardless of whether or not it was new. As with 4.1 and 4.2 above, it is the nature of the knowledge itself that is important in these circumstances; its newness is irrelevant.

What these examples illustrate is that there is only one safe approach to determining whether Mary's new knowledge refutes physicalism and whether a complete physical knowledge can be acquired inside a black and white room. This is to adopt the approach described at 4.3 above - which is to say, to leave the question of whether or not Mary can acquire a complete physical knowledge inside her black and white room open and examine the new knowledge itself. If it is valid knowledge of the physical and physical itself, then physicalism survives and it may be true that Mary cannot acquire all physical knowledge inside her black and white room. If not, physicalism falls, and it can be true that Mary can do so. The flaw in the Knowledge Argument as stated by Jackson is that it is so formulated as to:

� Stop this examination of the new knowledge itself being made;

� Predetermine the outcome of the examination that should have been made so that it favours the refutation of physicalism.

By assuming that all physical knowledge can be acquired inside the black and white room in our thought experiment, we ensure that any knowledge acquired outside of that room must refute physicalism simply because it is new. We need not examine the knowledge itself to determine whether or not it refutes physicalism. We have already determined through our initial assumption that if new knowledge is acquired then it must be knowledge of something non-physical that refutes physicalism simply because it is new. We have, in effect, pre-categorised any new knowledge as knowledge that will refute physicalism by assuming that all physical knowledge can be acquired inside a black and white room. In so doing, we have committed the ultimate scientific sin in constructing our thought experiment. We have assumed that we need not examine the nature of what we are studying because we already know all about it. Specifically, that we need not examine Mary's new knowledge to determine whether or not its nature is such that it refutes physicalism because we already know that it must be such that it refutes physicalism simply because it is new.

As the illustrations at 4.1 to 4.3 above show, however, this is not a safe assumption. The knowledge Mary acquires on leaving her black and white room can be new without refuting physicalism - if, for example, it is valid knowledge of the physical that is itself physical, it cannot reasonably be held to refute physicalism simply because it is new. It is therefore unsafe to assume that Mary's new knowledge refutes physicalism simply because it is new by assuming that all valid knowledge of the physical can be acquired inside a black and white room.

The Knowledge Argument is misconstructed. We begin knowing that Mary will learn something new on leaving her black and white room yet, knowing this, we assert that she can acquire a complete physical knowledge inside it, thereby presupposing that her new knowledge is knowledge of something non-physical.

5. The Knowledge Argument Reformulated

I do not suggest that Jackson's thought experiment should be abandoned. It is much too useful for this to be contemplated. My suggestion is rather that it be reformulated so as to remove the flaw - not with a view to ruling out the possibility that Mary can acquire a complete knowledge of the physical inside her black and white room but, rather, with a view to ruling the alternative possibility (that she cannot, in fact, do so) in. The reformulation below retains the sense and thrust of Jackson�s argument, entails what is probably the minimum possible weakening of premise A, but weakens it sufficiently to allow the possibility that Mary�s new knowledge does not necessarily refute physicalism simply because it is new.

Mary is a brilliant scientist who has only ever lived in a black and white room where her only access to the world outside is via a black and white television monitor. She lives at a time when scientists have developed, recorded, and prepared scientific justifications for, all true statements about the physical world, and Mary is able to acquire and understand a complete set of these - including a complete set of those describing the process of colour vision - inside her black and white room. If physicalism is true then, in so doing, she will also have acquired and understood the set of all true statements about reality - since physicalism is the view that reality is entirely physical and hence that the set of all true statements about reality is identical with the set of all true statements about the physical. Mary assumes she has acquired, both a complete knowledge of the physical, and a complete knowledge of reality inside her black and white room - until, that is, she leaves it. Then she learns something new. She finds out for the first time what colours such as red and green - previously known to her only as shades of grey - are really like.

This is potentially a problem for physicalism in that there are circumstances in which Mary's new knowledge could turn out to refute it. If Mary's new knowledge is either knowledge of something non-physical, or non-physical itself, or both, then we must conclude that physicalism is false.

There are, however, also circumstances in which Mary's new knowledge will not refute physicalism. Mary's new knowledge will not refute physicalism if that knowledge is:

� Physical itself;

� Valid knowledge of the physical that Mary could not acquire inside her black and white room.

In this second of the two cases that can hold, physicalism can stand - it can survive Mary's acquisition of new knowledge.

Before examining this new formulation in detail, it is worth noting that there is arguably a strong case for holding that knowledge of all true statements about the physical can be acquired inside a black and white room. We can safely assume, I think:

� That the physicalists outside Mary's room, who do not suffer the limitations that Mary does, can, given sufficient time, ingenuity, and instrumentation, acquire such knowledge of the physical;

� That they can then express this in a set of books and videos illustrated in colour;

� That they can then convert these to black and white but work to ensure that in every case where distinguishing between colours is vital to an understanding of a true statement about the physical, such a distinction is made clear in black and white (and shades of grey) and can be made by someone in a black and white room.

Suppose then that Mary in her black and white room has access to these books and videos, and also to remotely controlled instruments that allow her to repeat key experiments in black and white. Suppose further that she also has access to interactive instruction from the scientists themselves who do have access to colour information, do understand its relevance to the set of statements, and do understand the limitations placed on Mary and actively strive to overcome them. In these circumstances, there are, I submit, no grounds for holding that she cannot acquire knowledge of all true statements about the physical inside her black and white room. As long as she can distinguish between colours, albeit in black and white, she can learn to understand the contents of the books and videos and also make and understand the observations that support true statements and refute false statements. This being so, there is, I submit, no reason to suppose that she cannot acquire knowledge of all true statements about the physical inside her black and white room.

There is also good reason to believe that Mary will acquire new knowledge of what colour experiences are really like on leaving the black and white room. A simple comparison of our experiences of black and white films with the world of colour most of us usually inhabit is sufficient to justify the claim.

6. Physicalism Saved

The above re-working is, I believe, a better formulation of the Knowledge Argument than that usually stated - for two reasons:

i. First, it leaves open the possibility that Mary can learn all valid knowledge of the physical inside her black and white room (that knowledge of all true statements about the physical is all knowledge of the physical) and that, therefore, her new knowledge does refute physicalism. However, unlike the standard formulation, it does not rule out the alternative possibility that Mary's new knowledge is simply valid knowledge of the physical that cannot be acquired inside a black and white room (that it is valid knowledge of the physical that is not a statement). It does not assume that all valid knowledge of the physical can be acquired inside a black and white room and, in so doing, predetermine the outcome of the thought experiment by effectively defining any new knowledge acquired outside of the black and white room as knowledge that must refute physicalism simply because it is new. Instead, it recognises:

� That the real test of whether or not Mary's new knowledge refutes physicalism is whether or not the knowledge itself is valid knowledge of the physical that is itself physical.

� That it is this that then determines whether or not it is true that a complete knowledge of the physical can be acquired inside a black and white room.

The possibility at the core of the Knowledge Argument as usually stated - that Mary's new knowledge refutes physicalism - is recognised and included, but so is the alternative possibility that it does not.

ii. Second, and more significantly, by leaving open the question of whether or not it is possible to acquire all knowledge of the physical in a black and white room, and so, not closing off the possibility that Mary's new knowledge may not refute physicalism, it allows us to explore Mary's situation in more depth. This, in turn, permits us to investigate whether there is any set of circumstances in which physicalism can survive Mary's new knowledge, and to show that there is, in fact, one (and only one) such set - physicalism can survive if and only if all of the points below are true of Mary's new knowledge and, hence, of any quale:

6.1 If it is wholly experiential in nature and has knowledge content that cannot be expressed verbally without loss and is not entirely reducible to true statements about the physical.

We can agree, I think, that if physicalism is true then all true statements about reality must either be statements about the physical or deducible from or reducible to such statements. We can also agree that all such statements, being verbally expressible, can - if the argument presented at the end of section 5 above is correct - be acquired by someone in a black and white room. This being so, it is only possible for physicalism to survive Mary's new knowledge if it is experiential knowledge whose content cannot be expressed verbally without loss and is not entirely reducible to true statements about the physical. If it entails knowledge content that can be expressed verbally without loss, it can be expressed as a statement. If it is truly new, and really knowledge, then the statement will be a new true statement. But Mary has already acquired all true statements about the physical inside her black and white room. So any new true statement can only be knowledge of something non-physical and physicalism is refuted. If, on the other hand, what is acquired is experiential knowledge whose content cannot be expressed verbally without loss and is not entirely reducible to true statements about the physical, then it is, at least, possible for physicalism to survive its acquisition. It will survive if it is also true that it and, by extension, any quale, is valid knowledge of the physical that is itself 'made of' something physical.

6.2 If it is simply an additional way of knowing some part or parts of physical reality already encompassed within a complete verbally expressible knowledge of the physical.

If Mary can acquire the complete set of all true statements about the physical world inside her black and white room (and, in our thought experiment does, in fact, do so), then it must be the case that Mary already has a complete verbally-expressible knowledge about the whole of physical reality before she leaves the room. Her new experiential knowledge, therefore, can only be either another way of knowing some part or parts of physical reality she has already learned about inside her black and white room, in which case physicalism can stand, or it must be knowledge of something non-physical, in which case physicalism is refuted. If physicalism is true, therefore, Mary's new knowledge must be simply another (non-verbal) way of knowing some part or parts of the physical world for which she has already acquired at least one true statement about the physical. In short, her new knowledge - and any quale - must simply be an additional way of knowing some part or parts of physical reality already encompassed within a complete verbally expressible knowledge of the physical

6.3 If it is an 'inside observer's' perspective on this part or parts of physical reality, inaccessible to an outside observer of the part or parts in question (private knowledge).

Since (see 6.1 above) Mary's new knowledge must be experiential knowledge if physicalism is to stand, it must, by definition, be private knowledge, accessible in a given human organism, only to an inside observer of that organism and not to an outside observer of it. One person's experiential knowledge cannot be observed by an outside observer of that person (at least, not as experiential knowledge), it can only be observed by the person experiencing it - it is private as opposed to publicly accessible knowledge.

Notice that there is no implication here that Mary's new knowledge has no bearing on how she knows the outside world of yellow roses and red blood, green leaves and blue eyes, or brown muddy puddles and soggy-grey brain matter. Once she leaves her black and white room, all of these cease to be seen in shades of grey and are known to her in full colour. Nor is there a suggestion that the scientists outside of Mary's black and white room - outside observer's of Mary and of humans in general - do not have access to this world of colour. They do - or, at least, they do if they have fully functional visual systems - through their own private experiences of it. The significance of the conclusions drawn here and in 6.1 is not that Mary's new knowledge consists of some set of disembodied mental images accessible only to Mary. It is not even just that physicalism must deal with human private experiences if it is to survive Mary's new knowledge, although this is clearly an important implication. The point being made is not simply that physicalism must deal with human private experience if it is to survive Mary's new knowledge. It is that physicalism can only survive Mary's new knowledge if that knowledge is private and experiential knowledge. If all true statements about the physical human organism can be acquired inside a black and white room, then physicalism cannot survive Mary's acquisition of new knowledge on leaving the room unless Mary's new knowledge - and any quale - is (non-verbal) private and experiential knowledge that cannot be expressed verbally without loss.

6.4 If it is nevertheless valid knowledge of the physical.

If Mary's new knowledge is truly knowledge, then it can only be either valid knowledge of the physical or valid knowledge of something non-physical. If the latter is true, physicalism is refuted. Hence, if physicalism is to stand, it must be true of the knowledge content of both, Mary's new knowledge and of any quale that - private, experiential, and non verbally expressible or not - it is nevertheless valid knowledge of something physical.

6.5 If it is itself a wholly physical thing, so that it is really nothing over and above some physical part of the living human organism in a particular physical state.

If Mary's new knowledge is not itself an entirely physical thing - if it is not, in some sense, 'made of ' something physical - then it must be, either partly or wholly, a non-physical thing. If physicalism is to stand, Mary's new knowledge, private, experiential, and irreducible to true statements about the physical or not, must be entirely reducible to, and identical with, something physical - it must be really nothing over an above some physical part of the living human organism in a particular physical state. To put it in slightly different terms, if physicalism is true, and the qualia that encapsulate Mary's new knowledge exist, then it must be the case that there are some physical things that are also qualia - that it is true of any and every quale that it is an entirely physical thing.

6.6 If it is simply an inside observer's way of knowing this physical part of the living human organism in a particular physical state - a different perspective on an aspect of physical reality known to an outside observer as a subset of the flesh, blood and brains view of the organism.

As has already been argued in 6.5 above, if it is not true that Mary's new knowledge is really nothing but one particular aspect of the physical reality of Mary in a particular physical state, then physicalism is refuted. If it is true (as it must be if physicalism is to stand), it must be the case that some aspect of Mary's new knowledge - a red quale, say - is an additional way of knowing that particular aspect of the physical reality of Mary in a particular physical state. If Mary's red quale is really nothing over and above one particular aspect of the physical reality of Mary in a particular physical state, then when that particular part of Mary enters that physical state, Mary experiences a red quale. That red quale will have been caused, in the case of Mary leaving the black and white room, by some external reality such as a red rose, and can therefore be considered as a way of knowing that red rose. However, it occurs in Mary because that physical part of her has entered that physical state. It is reasonable to suppose that it (the physical state) can be made to occur by stimulating the event directly without involving an external element like a red rose - through direct stimulation with an electrode, say - and, if it is so stimulated, Mary will still experience a red quale. She will know that physical aspect of herself in that physical state as (and via) a red quale. Thus, whilst Mary's red quale may well be some facet of her knowledge of a red rose, there is also a sense in which it is a way of knowing the physical part of Mary in a particular physical state that �just is� the quale. It must, that is to say, be an additional 'inner' perspective on an aspect of physical reality known to an outside observer as a subset of the flesh, blood and brains view of the organism.

6.7 If it is simply one limited view of that physical reality - the reality as known as distinct from the reality as such.

If I am unaware that the morning star and the evening star are both the planet Venus, I may think of one view as 'the morning star' and the other as 'the evening star' and consider them, explicitly or implicitly, as different realities. Once I come to know that each is a different (and limited) perspective on the planet Venus, it becomes both valid and necessary to recognise each as the reality (of the planet Venus) as known (in particular limited circumstances) as distinct from the reality as such. Similarly, since a red quale is only one of two perspectives on the particular part of physical reality that it is, it is both valid and necessary to distinguish it as the reality as known as distinct from the reality as such. To fail to do so is to implicitly assume that this limited view of the reality in question is the reality in question. It is to assume that there is no more to the reality in question than is known via this limited perspective - effectively, that there is no wider outside observer's flesh, blood and brains perspective on the reality in question. But if physicalism is true, then a red quale 'just is' something physical, which means that there must be more to knowing it than is known of it via the red quale. If physicalism is true, therefore, it must be the case both that the red quale is really nothing over and above some physical reality and that it is nevertheless the reality in question as known as distinct from the reality as such. As I shall show below (9.2), these positions may appear contradictory but are, in fact, entirely compatible with each other. They are, moreover, the key to resolving a number of conundrums associated with the mind-body problem (see 8.1 - 8.4 below).

6.8 If the outside observer's view of it is also the reality as known as distinct from the reality as such.

This is essentially the same argument as that presented in 6.7, although there are also additional supporting factors in this case. If physicalism is to survive Mary's new knowledge - a red quale in the instance described above - then the red quale must (as argued in 6.5) be an entirely physical thing known to an outside observer as a subset of the flesh, blood and brains view of the organism. Since this view is made up of such things as electrochemical reactions and firing neurons, it clearly does not encompass the red quale perspective on the physical reality in question. Like the red quale perspective itself, it is an incomplete view of the underlying reality - so that it is, once again, both valid and necessary to distinguish it from the reality as such by categorising it as the reality as known. To do otherwise is to mistake a particular perspective on the reality in question for the reality itself.

In this instance, there is additional supporting evidence for the position. Although I have focused for the sake of simplicity on the idea that Mary's new knowledge is only knowledge of the colour red, in reality she would, on leaving her black and white room, begin to experience everything - including the outside observer's flesh, blood and brains view of other humans - in colour. Clearly, therefore, this view is itself a private perspective in the experience of an outside observer and hence, must be something other than the reality of the other human that the outside observer is observing.

Moreover, it should, in any case, be self-evident that the outside observer's physical view is the reality as known as distinct from the reality as such. In this instance, the observer is clearly physically distinct from the reality observed and can only have access to it via his own senses and thoughts which, since he is an outside observer, can only, by definition, be something other than the reality itself - the reality as known as distinct from the reality observed.

7. Only One Solution to the Mind-Body Problem can save Physicalism.

What emerges from this is a perspective on the relationship between qualia and the physical in which:

7.1 A quale is both:

� Really nothing but an entirely physical aspect of the reality of the living human organism known by an outside observer as a subset of the flesh, blood and brains view of the organism

� The reality as known as distinct from the reality as such � an inside observer�s limited view of the physical reality that �just is� the quale.

7.2 The outside observer's perspective is also the reality as known as distinct from the reality as such - an outside observer's experiential perspective on a single reality with two sets of characteristics, one experienced and observed by an outside observer of the living human organism, the other experienced and observed by an inside observer of the living human organism

7.3 Since each perspective is a product of a different mode of observation, each can exist without the other. Indeed, they will exist together only in highly unusual circumstances - for example, in circumstances where a scientific observer is making a specific effort to observe both his own brain via a video camera as an outside observer of it and directly stimulating the physical event that is the quale (to himself as inside observer).

7.4 The outside observer's flesh, blood and brains perspective does not give rise to or transform itself into the inside observer's perspective. The flesh, blood and brains perspective is what the quale is 'really like' when experienced and observed by an outside observer, but it is a way of knowing the reality of the quale that exists in an outside observer's experience, not the reality of the externally observed quale as such. The inside observer's perspective is what this underlying reality is 'really like' when experienced by an inside observer and is also this reality as known as distinct from the reality as such. It is another observed characteristic of the reality that underlies the flesh, blood and brains perspective and it is this underlying reality that gives rise to it. It is a characteristic of that reality, not a characteristic of the flesh, blood and brains view of it (which is, after all, only a view of that reality in the experience of another observer). One set of experienced characteristics (those of an external observer of the reality underlying the quale) does not give rise to, or transform itself into, another (those of an internal observer of the organism that encompasses the quale). Instead, the underlying reality is the 'root cause' of both sets of characteristics.

7.5 Scientific study of this underlying reality is based on observations made by an external observer of it, but it is the reality itself that is studied. The observation is done via the outside observer's flesh, blood and brains view of the reality, but it is the underlying reality whose behaviour in various different experimental circumstances is observed and then described verbally in the form of true statements about the physical quale to give us a complete propositional account of its nature.

This complete propositional account explains every characteristic of the whole of the underlying reality in every physical circumstance:

� Since it is entirely verbally expressible, it does not, of itself, encompass the experiential knowledge of what this underlying reality is really like to an outside observer - the non-verbal experience entailed within the outside observer's flesh, blood and brains perspective on that reality. Used in conjunction with this experiential view, however, it does explain why it is like it is in these circumstances. It explains the characteristics of the outside observer's experienced flesh, blood and brains view of the quale in the only way possible - by specifying what physical things have these characteristics, how they differ from other physical things that do not, and how these differences account for the differences in the experienced characteristics of the physical things in question.

� Similarly, since the inside observer's perspective must, if physicalism is true, be really nothing but that underlying physical reality, the complete propositional account of the underlying reality, whilst it cannot, being an entirely verbal account, encompass knowledge of what the reality is really like to an inside observer, can (since it does encompass the whole of the reality and is a complete propositional account of its nature) explain why it is like that. It can explain the characteristics of the inside observer's experiential view of the quale (experienced redness for example) in the same way as it explains the characteristics of the outside observer's experienced flesh, blood and brains view. It can specify what physical things have these characteristics, how they differ from other physical things that do not, and how these differences account for the differences in the experiential characteristics of the physical things in question. It can, moreover, answer in the same fashion, related questions like why experience exists at all.

7.6 The complete propositional account of the underlying reality should entail sufficient information to enable the reality to be re-created, together with all of its characteristics, the inside observer's experiential view, as well as the outside observer's. A human scientist would, no doubt, need the outside observer's experiential perspective to be available to him in order to be able to translate this information into the actual operation of re-creating the reality. However, an alien with entirely different sensory system should also be able to re-create the reality in a human, provided it could accurately and exhaustively map its own outside observer's sensory perspective on the human to the propositional account.

This does not mean, however, that the complete propositional account, of itself, encompasses a complete physical account of the quale. Since:

� If physicalism is true, experiential knowledge must be valid knowledge of the physical that cannot be expressed verbally and must therefore be included in any complete physical account as experiential knowledge.

� An alien with different sensory systems who had a complete propositional account of the whole human organism could not have a complete view of the physical reality of the organism because it would not know that it was characteristic of that physical reality that it experienced the world, including itself, in these ways.

� It is impossible to fully explain why the human organism is like it is without encompassing what it is like to both an internal and an external observer and mapping each to the other and to the propositional account.

It follows that a complete physical account of the quale must encompass, not only the complete propositional account, but also:

� The experiential perspectives of both the outside observer and the inside observer;

� A mapping of each to the other and to the propositional account.

The potential importance of this analysis and its outcome will, I think, be evident. If the arguments presented hold, the clear implication is that if:

� Physicalism is true;

� Mary learns something new on leaving her black and white room;

� All true statements about the physical can be learned inside a black and white room;

then the relationship between qualia and the physical described above must be the solution - or, at minimum, the core of the solution - to the mind-body problem. Moreover, since:

� Physicalism itself has so far proved itself adequate to deal with every other aspect of reality we have studied over many centuries;

� Both the claim that Mary learns something new on leaving her black and white room and the claim that all true statements about the physical can be learned inside a black and white room are themselves plausible (see end of section 5 above);

there are arguably good grounds for holding, as a working scientific hypothesis, that this view of the mind-body relationship is the correct view of that relationship.

8 Additional Support for this Perspective on the Relationship between Qualia and the Physical

As may be evident from the description in section 7 above, further support for the account can also be found from sources beyond the knowledge argument. As follows:

8.1 Leibniz's Law.

Since the position proposed here is clearly a form of identity theory, a look at how it relates to Leibniz's law on the identity of indiscernables will make a good beginning. The law states that if x is y, then any property of x is a property of y. This would be a problem if the claim being made was that Mary's new experiential knowledge of red was identical to some part of the 'flesh, blood and brains' Mary as observed by outside observers of her. If the claim was that Mary's red quale was identical with or really nothing over and above what the outside observer of Mary, given suitable equipment, knew as a few interconnected brain cells (say). It is clear that redness is not a property of what Mcginn 1989 has termed the 'soggy grey matter' of Mary's brain as an outside observer would know it, and equally clear that greyness and soggy solidness are not characteristics of Mary's experienced red. This, however, is not what is being claimed here. The claim is that some part of the reality that underlies what an outside observer of Mary knows as the Mary of flesh, blood, brains and cells is the same reality that Mary knows as experienced red. The identity resides in this underlying reality - and the experienced red that Mary knows as an 'inside observer' of it, and the soggy grey matter that others know (or experience) as outside observers of it, are both characteristics of the underlying reality in question.

There is thus no conflict with Leibniz's law, either in this respect or in any other:

� The fact that 'experienced redness' is not a property of the 'soggy grey matter' of Mary's brain and vice versa is not a problem, because both are characteristics of this single underlying reality that is the real basis of the identity.

� The fact that public observability is not a property of experienced redness, and private observability is not a property of soggy grey matter, and that anything public is, by definition, not private, and vice versa, is not a problem. There is no difficulty because it is characteristic of the single underlying reality, both that it can be known publicly, and that it can be known privately.

� The fact that every aspect of what the outside observer knows as soggy grey matter has a precise location in physical space and the experienced red known by Mary, the inside observer, is impossible to locate in physical space is not a problem. Again, locatability in public space and knowability in terms of private experiences that cannot be so located are both characteristic of the underlying reality in which the identity resides. The reality known by an inside observer as a private experience can be located in public space when known and observed publicly by outside observers. It is simply that, when it is known privately, it is known in a way which makes location in space impossible.

8.2 Kripke's Problem for Proposed Identities.

Because the position proposed in this paper is a kind of identity theory, a question arises about how it deals with a problem raised by Kripke (1980 - see also Chalmers 1996 on this topic). According to this, Leibniz's Law demands that if A is B then A is necessarily B. There are no circumstances in which this is not true - it is true in all possible worlds. There are examples in the world of identities where this may appear to be false - where it appears we can conceive of possible circumstances in which the identity does not hold. However, if there is true identity, these must arise from a misconception of some kind, and it will be possible to discover and specify the basis of the misconception. If we propose an identity for which it is possible to propose plausible circumstances in which it does not hold, but not possible to give an equally plausible account of why these conceivable circumstances do not threaten the identity claim, then there are clear grounds for abandoning the claim. If A and B are identical - if they are in all cases inseparable from each other - then there can be no circumstances in which the two can be conceived of as separate that are not based on a misconception. If there are such circumstances, then we have evidence that the two are separable and so cannot reasonably be thought of as identical.

Water and H2O provide a good illustration of this point. If water really is identical to H2O - and it is - then there are no circumstances in which water can exist and not be H2O, they just are the same thing and cannot ever exist separately. It appears that we can conceive of a situation in which this is not true, but this is based on a misconception. Thus, we can imagine a possible world in which water is not H2O but XYZ - but this, to quote Chalmers (1996), is illusory. In fact, we are conceiving of a situation in which there exists something that has all the properties we normally associate with water, but is not actually water. It therefore does not present a problem for the assertion that water is H2O, because it is not an instance of water not being H2O, only an instance of something like water not being H2O.

This is an illustration of a situation in which the identity only appears to be threatened. An illustration of the opposite situation - in which there is genuine evidence that the claimed identity must be abandoned - is a proposed identity between pain and (say) firing c-fibres in the brain. If the two truly are identical, then it should either be impossible to conceive of situations in which the two are not identical or, if it is not, it should be possible to give a plausible explanation of why these situations do not provide evidence against the proposed identity. In fact, in this instance, it seems to be possible to conceive of such situations, but not to explain why they do not provide evidence against the proposed identity. The idea of disembodied pain seems to us to be plausible, as does the idea of a zombie who has the firing c-fibres, but no feelings. In this case, we cannot plausibly argue that we are mistaking something like pain for pain itself or something like firing c-fibres for actual firing c-fibres. Pain is pain. Something that feels like pain just is pain, it cannot plausibly be regarded as something that feels like pain but is not pain in fact. We therefore have a plausible circumstance in which actual pain is separable from firing c-fibres and, hence, evidence against the identity claim. Similarly, firing c fibres are either firing c-fibres or they are not. It is actual firing c-fibres that we can plausibly regard as being disassociated (in zombies) with feelings, not something that seems like c-fibres but is not. In this circumstance, therefore, there is, it appears, evidence that the identity does not hold.

The identity I have proposed here, of course, is between the reality underlying our outside observer's flesh, blood and brains view of the relevant aspect of the human organism and the reality known by an inside observer as a quale (as pain or experienced red) - the claim that there is one reality that can be known in two different ways. Not only that, but it is entirely possible for it to be known in one way at a particular point in time, but not known in the other. An 'inside observer' of the human organism may know it as an experience but not as something made of the soggy grey matter of the brain, and an outside observer may know it in this way but not as an experience. It is also extremely difficult for one person to have and hold both views of the reality in question at the same time. It is therefore entirely possible that we should regard disembodied experiences and zombies without feelings as plausible but this does not mean that the proposed identity is threatened. Because the underlying reality can be known in these different ways separately, and probably cannot easily be known in these different ways simultaneously by any one of us, it is no surprise that we consider it plausible that one could exist without the other - but this does not mean we are right to do so. Clearly, each of the two ways of knowing can and do exist without the other if the observational circumstances dictate this, but this is not plausible evidence against these simply being different ways of knowing one underlying reality and does not, I submit, threaten the form of identity proposed in this paper.

8.3 "Soggy Grey Matter": A Sub-set of "Technicolor Phenomenology".

This distinction between the 'soggy grey matter' of Mary's brain as observed by an external observer of Mary and the actual reality underlying it is an important one in other respects. Colin McGinn (1989) has famously asked 'How can technicolor phenomenology arise from soggy grey matter?', suggesting that physical matter is so different from something like experienced redness that it is impossible to conceive of how qualia could possibly 'arise' from the physical reality of the flesh, blood, brains, cells, and atoms of the living human organism and arguing that the mind-body problem may ultimately be irresolvable. However, if the perspective suggested by the analysis in this present paper is correct, his question is expressed in a misleading way. The desire to explain the 'technicolor phenomenology' of the world of consciousness and qualia in physical terms is sound, of course, but it is misleading at best to express it in the terms used by McGinn.

It is the reality of the human organism that 'gives rise to' McGinn's 'technicolor phenomenology�; although it might be more correct to say that the technicolor phenomenology is a characteristic of that reality. The success of science as a means of acquiring reliable knowledge is based on observation and measurement by outside observers of the human organism. The human organism when observed from the outside is known as something made of flesh, blood, cells, atoms, and soggy grey matter. It therefore seems natural to think of the flesh, blood, cells, atoms, and soggy grey matter as the reality of the human organism and to ask how this 'gives rise to' the technicolor phenomenology that is evident when we know this reality as inside observers - natural, but incorrect.

What science observes and measures in the public world in respect of the human organism is undoubtedly the reality of the human organism; there is no question about that. Nor is there any doubt that what we know when we observe and measure the human organism in the public world - the soggy grey matter, the flesh, blood, cells, and atoms - is what the human organism known by an outside observer is 'really like'. What science observes and measures really is the physical human organism, and it really does have the subdivisions (and subdivisions of subdivisions) that we discover when we examine it in depth. And what we observe and measure is the reality of the human organism. If it were not, science would not be successful in acquiring reliable knowledge about it in the way that such things as medical advances show that it clearly is. When we talk about soggy grey matter, however, and about the fleshiness of flesh, the solidity of bones, the redness of blood and so on, we are not referring to the reality of the organism itself. What we are referring to is that reality as experienced by outside observers of the human organism. We are describing, not the reality itself, but how the reality of the human organism observed in the public world affects the private experience of the various human observers. These private experiences - from the redness and stickyness of blood to the soggyness and greyness of the brain - do not give rise to McGinn's technicolor phenomenology. On the contrary, they are themselves part of the technicolor phenomenology we are seeking to explain. We cannot conceive how this technicolor phenomenology can arise from soggy grey matter because the question itself misdirects us:

� It creates an artificial gulf between �the mental� and �the physical� by associating each with aspects of the technicolor phenomenology that have very different 'feels' and then taking these very different feels as evidence of a major gap between the two - when, in fact, both are just different aspects of what we are trying to explain.

� It asks, in effect, how one set of private experiences 'gives rise to' another - how one way of knowing the reality of the human organism gives rise to another way of knowing it.

Arguably, misconceptions of this kind are one reason why there is felt to be an 'explanatory gap' between the physical and the phenomenological. In fact, our 'soggy grey matter' (the experience, as opposed to the reality that underlies it) is as much a facet of McGinn's technicolor phenomenology as is a red quale or an imagined unicorn. All are characteristics exhibited by the reality of the human organism in particular circumstances, and it is not sensible to ask how one gives rise to another. Rather, we should ask how the discovered nature of the actual reality examined and measured by science - by observing the effects of placing it in various controlled experimental conditions on the private experiences of human observers - accounts for all of these aspects of our technicolor phenomenology, including those aspects we refer to as 'soggy grey matter'.

8.4 The 'Hard Problem' Resolved.

Others who have addressed the problem of giving a satisfactory physical account of the world of consciousness and qualia, have also seen a gulf between the two that at times has seemed unbridgeable. One of these is David Chalmers, who has identified what he has described as the 'hard problem' of consciousness. For Chalmers, this problem is uniquely hard. So hard that what we have come to regard as normal scientific explanation will not do, and it is necessary to resolve the difficulty by taking experience itself as a fundamental feature of the world alongside mass, charge, and space-time. In fact, if the perspective on the mind-body relationship that emerges from the analysis of the Knowledge Argument presented in this paper is correct, this is not true. There is no hard problem, and no need to take the relatively drastic step proposed by Chalmers.

If I understand him correctly, what Chalmers refers to as 'the hard problem' (1995) has three aspects:

� There is something it is like to be a human organism - something it is like to entertain a mental image or experience an emotion. If we can give a scientific account of everything we can as external observers observe about a rock or an automobile, we can be fairly confident that we have given a full account of it, but this is not the case with the human organism. If we compile a full scientific external observer's view of the human organism then there is still something left to explain - why is the fact of being this physical organism accompanied by experience? Why is there 'something it is like' to be a human organism - to entertain a mental image or experience an emotion? Why is being a human organism (and possibly other advanced organisms) 'like' anything?

� This experiential aspect of the organism is not reducible to the physical as we presently understand it and, in such circumstances, 'non-reductive explanation is the natural choice'

� The 'hard problem' - explaining why there is 'something it is like' to be a human organism, or to entertain a mental image or experience an emotion - is not susceptible to any explanation based on the physical as we presently understand it. Consequently, a theory of consciousness must and should take experience itself as a fundamental feature of the world alongside mass, charge, and space-time.

As may be evident from 7.5 above, however, the perspective described in this paper offers another simpler account, more compatible with the physicalist view as currently held by most scientists. According to this perspective, the knowledge content of the inside observer's experiential view of a quale is irreducible to the knowledge content of the outside observer�s view of it. However, there is no more to the reality of the quale than there is to the reality known by an outside observer as an entirely physical thing, simply more to knowing it than is known by an outside observer knowing it in this way. There is an additional experiential view of this single entirely physical reality that is accessible only to an inside observer of it, and is irreducible to an outside observer's view of it. However, this additional view is nevertheless wholly encompassed within the entirely physical reality underlying the outside observer�s view. It is not an additional part of the reality over and above that known by an outside observer (the quale is both the reality as known as distinct from the reality as such and really nothing but the reality as such).

In this perspective:

i. There is a single reality underlying the view held by both observers. A quale is what this underlying reality is �like� when experienced by an inside observer of the human organism it occurs in, and an aspect of the flesh, blood and brains view of the organism is what it is �like� when experienced by an outside observer. Each is a characteristic of the underlying reality and can be accounted for via a scientific study of that reality

ii. There is no �hard problem� of consciousness. A scientific study of the underlying reality would be considered sufficient to account for what the reality is like to an outside observer experiencing it in terms of the flesh, blood and brains view of the organism. There are no grounds for holding that it cannot also be considered sufficient to account for what the reality is like to an inside observer experiencing it as a quale (or, indeed, for why it is like anything at all). We can account for the characteristics of the underlying reality as experienced via the inside observer�s quale in the same way as we can account for its characteristics as experienced via the flesh, blood and brains view of the organism: by specifying what physical things have these characteristics, how they differ from other physical things that do not, and how these differences account for the differences in our experience or, indeed, for the very existence of experience.

iii. Experience is not �left out� of the scientific account, as is sometimes the case with physicalist accounts. The experiential element of any and every quale must be encompassed as an experience in any scientific account claimed to be complete. This is so for two reasons:

� Since the experiential element cannot be expressed verbally without loss, it can only be encompassed as an experience, and since, if physicalism is true, it must be valid knowledge of the physical, it cannot justifiably be left out of any account claimed to be complete

� Any account that attempts to explain experience must encompass what it aims to explain � which is to say, experience itself.

Once this is recognised, it becomes clear that there is no mystery here � no problem that is particularly hard. A quale is an entirely physical thing that also happens to be the basis of human experience. Different essential experiences (redness, sweetness etc.) have small physical differences that account for the differences in the associated experiences. All qualia have one or more physical features that make them different from other physical realities that lack an experiential characteristic � differences that explain why being a human organism or, indeed, any �higher� animal is �like� anything. A verbally expressible account of these differences is a complete account of the differences themselves, sufficient to allow an outside observer of a given human to re-create a physical environment inside that human which exhibits (to �the inside observer� of the human in question) the experiential characteristic they give rise to. Of itself, it is not sufficient to account for why being human is �like anything�, but only because a purely verbal account cannot encompass experience � the very thing we are seeking to explain.

If a purely verbal account - or an explanation in terms of what Chalmers calls �the physical as we presently understand it� � fails to explain why being human is like anything, it is not because the explanation itself is insufficient. Nor is it because it fails to encompass some aspect of the underlying reality in its account. It is because, being purely verbal, it fails to encompass knowledge of what the reality is �like� to an inside observer and so cannot complete the account. If a stone and a human are different because there is a �something it is like� to be a human but not a �something it is like� to be a stone, a physical account of humans that does not encompass this �something it is like� is incomplete for two reasons. First because it misses out a crucial part of the physical description of humans that indicates how they differ from stones. Second because, as a result, it cannot then encompass a prepositional explanation of why they differ in this way. The problem, however, is not a lack of prepositional information, but the inability of verbally expressible prepositional information to encompass the very characteristic that needs explaining - a problem easily resolved by simply encompassing experience within our complete knowledge of the reality in question. With the experiential characteristic encompassed within the total view as an experience, our account can state �these physical things are unique in having �this� experiential characteristic and this, in propositional terms, is why. Without it, our account cannot adequately encompass how they are different, and cannot � because of this � state why.

iv. The problem of experience can be solved without taking experience itself as a fundamental feature of the world, alongside mass, charge, and space-time. It does become a characteristic of this world - an attribute of certain physical things, likely to alter our perception of �the physical� - but it need not be added as a fundamental feature. At worst, there will turn out to be a requirement to add a fundamental feature to our current view of the physical world as a result of our attempts to explain what it is about the reality underlying a quale that explains experience. However, should such a requirement arise, the new fundamental feature will not be experience itself but something more similar to space, charge or space-time (an entirely different proposition, more likely to find acceptance with within the scientific community).

This kind of explanation will not answer those who wish to ask (for example) why the universe is such that there are some physical things that are also qualia - questions of the kind that require us to choose between answers like 'god made it that way' or 'it was just a matter of chance, strange as it may seem'. Such questions, however, are of a type that scientists are usually content to leave to others, preferring to focus on the more practical considerations that an explanation of this kind can and does address - including, for example, how can we build or otherwise create something that has these characteristics (like a conscious robot should such a thing be non-organically feasible). The kind of explanation presented above will suffice for these purposes, and will, I believe, be regarded by most scientists as entirely satisfactory.

9 Final Points.

Up to this point, I have considered only points in favour of the perspective on the mind-body relationship proposed in this paper. In this final section, I want to conclude my case by considering some aspects of the position that raise questions and to show that there are reasonable answers to these questions � that the difficulties they seem to point up are more apparent than real.

There are apparent difficulties with the view in five areas:

9.1 There is the appearance of self-contradiction in a position that asserts both that any given quale is really nothing but, or entirely reducible to, some physical reality and that there is more to knowing it than the complete set of true physical statements about the physical thing in question. If there is only a single reality involved, and a complete external observer�s knowledge of that reality entirely encompasses all of that reality, how can it be possible that the inside observer's way of knowing that reality entails additional knowledge content?

This seems problematical because:

� On the one hand, if the reality encompassed by the inside observer's knowledge is entirely encompassed within the complete external scientific observer's knowledge, it cannot be true that there can be additional knowledge content in the inside observer's view due to an additional part or aspect of reality being known.

� On the other, we have centuries of experience that seem to show that the complete external scientific observer's knowledge of anything else in the universe is a complete knowledge of the thing in question, sufficient to account for every aspect of its observed behaviour. From this, it seems to follow that, even if we have reason to believe, in the case of the human organism, that the inside observer�s view entails an additional perspective, we can have no reason to suppose that this would entail additional irreducible knowledge content.

In fact, while the first of these points is undeniably correct, and will not be disputed here, the second is not. It is entirely possible to suggest plausible circumstances in which it will not hold true - and to do so without disputing the claim that the complete outside observer's propositional knowledge is sufficient to account for every aspect of observed behaviour.

Notice that it is true of any reality in the world, that an outside observer can only ever know it in relation to other things:

� His own sensory experience of it, with or without the enhancements possible through instrumentation;

� Its size in relation to some physical constant;

� Its position in space relative to other objects and some accepted frame of reference;

� Its behaviour or nature in relation to particular experimental circumstances and our physical and chemical theories;

� And so on.

Notice also that in the case in question it is entirely plausible to suggest that an inside observer knows qualia more directly than this. In this case, there is no physical separation between the observer and the observed or the knower and the known, so that it is, at least, possible that the inside observer knows qualia, not in relation to other things, as an outside observer must, but non-relationally - that they are known as is, by direct acquaintance, in relation only to themselves.

Non-relational knowledge would have minimal information content, and would not and could not entail any knowledge that could be used to predict behaviour (if the thing known is known only in relation to itself, nothing can be known about its behaviour since this implies relationships to other things). However, it is entirely plausible that it should contain knowledge content that is irreducible to an outside observer's relational knowledge. To know something relationally is to know it indirectly, in relation to other things or perspectives, and so (perforce) to know it other than directly and non-relationally by direct experience.

It is also entirely plausible to suggest:

That relational knowledge is verbally expressible knowledge - that its content can be expressed entirely in terms of labels for things and relationships observed in the world by an outside observer.

That non-relational knowledge acquired by direct experiential acquaintance cannot be expressed verbally without loss of knowledge content. On the one hand, its content, being a single non-relational experience, cannot be expressed in terms of relationships to other things. On the other, a label such as 'red' that we might assign to it cannot, being verbal, entail the experiential knowledge itself (Mary in her room could acquire the label but not the experience).

- a further indication that it is entirely plausible that it should contain knowledge content that is irreducible to an outside observer's relational knowledge.

9.2 There is also the appearance of self-contradiction in a view that asserts both that any given quale is really nothing but, or entirely reducible to, some physical reality and that it is nevertheless the reality in question as known as distinct from the reality as such.

It may appear that there is a contradiction here. On the one hand, there is an assertion that the quale is nothing but or nothing over and above some physical reality � that it simply is that reality. On the other, there is an additional assertion - that the quale is the reality of that one thing as known - which may seem to imply that there are two things (the reality as known and the reality itself). In fact, it is entirely possible that both assertions are true.

A solid plastic cube has a characteristic we might describe as its 'cubishness'. This 'cubishness' is embodied by the solid plastic cube itself - in reality, it is 'nothing but' the solid plastic cube. We can safely say that there is no more to this cube's 'cubishness' than the cube itself - that it just is that cube. But suppose the cube then exhibits a new characteristic which we can call 'squeeginess'? Suppose that, as its temperature gradually rises, it loses its cuboid cohesion and 'melts into' a series of new shapes that are progressively more rounded and lumpy and less cube-like? Do these two sets of circumstances not illustrate a situation in which it is accurate to say that 'cubishness' is nothing over and above the reality of the solid plastic cube, but also accurate to regard it as one perspective on that cube - in effect, one limited way of knowing it? Do they not also illustrate a situation in which - despite the fact that the 'cubishness' is, in real terms, nothing but the reality we are distinguishing it from - it would be both, accurate to distinguish between the reality of the cube itself and the (one, limited) 'cubishness' perspective on it, and necessary to do so?

This is all that is being asserted here about qualia. The claim is that any given quale is entirely embodied by an aspect of the physical reality of the human organism, but that it is nevertheless both accurate and necessary to distinguish between the reality itself and its 'qualeishness'. The �qualeishness� is the reality, but the view of the reality it affords us is only one of two limited perspectives on it. It is therefore both accurate and necessary to distinguish between the reality as known (the �qualeishness�) and the reality as such, even though there is no actual physical distinction between them.

The claims made here regarding qualia are thus entirely plausible - it is not necessarily a contradiction to claim both that a quale, considered as a reality, is really nothing over and above some part of the physical human organism, and that, considered as a way of knowing, it is the reality as known rather than the reality as such.

9.3 The idea that a quale, known experientially as a quale, is an �inside observer�s� perspective on an aspect of the physical reality of the living human organism may appear to be a problem for a position claimed to be scientific. Observation is the basis of all science, and nothing like a quale has ever been observed inside the flesh, blood and brains view of the organism, nor is ever likely to be.

In fact, there is no problem here, only a need to clarify the relationship between the two perspectives. The inside observer�s perspective is a perspective whose existence is inside the reality of the aspect of the physical human organism in question, but it is not inside the outside observer�s view of that reality as a subset of the flesh, blood and brains perspective on the human organism. The outside observer�s perspective is not the reality that contains the inside observer�s perspective, it is itself a way of knowing that reality that exists in the experience of the physically separate outside observer. An outside observer�s experiential view of the reality of another human cannot be reasonably held to �contain� the reality itself in any physical sense, only to reflect the observed nature of that reality, so it cannot be reasonably held to contain the inside observer�s perspective either. In fact, since the outside observer�s perspective on another human is itself one part of the total set of human experiences, it, properly speaking, is a subset of the total inside observer�s experience of human reality, not a �container� for it. Consciousness is not inside the brain, and we should not expect to observe it (or the qualia it entails) there. On the contrary, �the brain� as experienced by an outside observer is inside consciousness � an accurate, experiential, 4-dimensional, map of the reality of the organism as known by an outside observer that cannot be reasonably held to contain anything other than smaller and smaller sub-divisions of itself.

9.4 The idea that qualia, known experientially as qualia, should be regarded as valid knowledge of the physical and encompassed in a complete physical account may seem to be unscientific and to undermine the physicalist account we are trying to defend. In fact, this proposed inclusion of experiential knowledge in a scientific account in no way undermines the scientific approach and should not concern us unduly.

Note, first of all, that if we broaden our perspective from that of a single quale to that of the whole human organism, the position as stated in 7.6 above can be restated and expanded as follows:

A complete scientific knowledge of the physical human organism comprises all of the following, but only all of the following:

� A complete set of all true statements about the physical human organism that express the outside observer's view.

� A complete set of the irreducible non-verbal experiential elements that are valid knowledge of the physical but cannot be encompassed within the set of true statements because they cannot be expressed verbally without loss.

� A mapping of each of these to its externally observable correlate or (more likely) correlates in the flesh, blood and brains perspective on the organism, and to all associated true statements.

This follows from the arguments in section 6 and 7 above. A complete view must encompass all three elements. If all qualia are valid knowledge of the physical that cannot be encompassed within the set of all true statements about the physical human organism, then they are valid knowledge of the physical that must be added to this set of statements in any view of the physical human organism claimed to be complete. And if they are simply an inside observer's private or experiential view of something an outside observer knows in terms of the flesh, blood and brains perspective, then any complete view of the physical human organism must also entail a mapping of these various qualia to their externally observed correlates and all associated true statements.

It must encompass only these three elements because:

� A complete set of all true statements about the physical human organism encompasses all possible propositional knowledge of the physical human organism and cannot be added to propositionally if physicalism is true.

� Physicalism can only survive Mary's new knowledge if that knowledge is comprised of non-verbal private and experiential elements. Anything other than non-verbal, private and experiential, qualia would refute physicalism, an important point because it means that, other than such private and experiential non verbally expressible elements, anything of the mental world must be encompassed within the set of true statements about the physical human organism. In other words, it must be possible to account for all things mental in terms of all true statements about the physical human organism plus (only) this additional non-verbal experiential knowledge.

� If the points above are true, only qualia, their flesh, blood and brains perspective correlates, and the true statements about the physical encompassed in the associated prepositional accounts, need be or can be mapped.

This is a view that encompasses qualia as qualia, but it does not, I submit, undermine the scientific approach. Neither the idea that such experiences can be regarded as valid knowledge of the physical, nor the idea that a completed physical account of the world, including the human organism, must encompass qualia as experiences need concern us unduly. Regarding qualia as valid knowledge of the physical does not threaten the scientific approach. On the contrary, if qualia exist, and encompass knowledge of something, considering them as anything other than valid knowledge of the physical means categorising them as valid knowledge of something non-physical, a position that entails the refutation of physicalism. It is taking the opposite stance that is a threat to the commonly held scientific approach to understanding the world. And including qualia as experiences in a completed physical account of the human organism is then both, essential and � arguably � non-controversial:

� If qualia are valid knowledge of the physical, they must be included somehow in any scientific account of the human organism that is claimed to be complete.

� If their knowledge content cannot be expressed verbally without loss, they can only be encompassed within such an account as experiences, they cannot be encompassed propositionally. They are characteristics of that aspect of physical reality we call the living human organism that a purely prepositional account fails to capture.

� If their knowledge content cannot be expressed verbally without loss then it is knowledge content that cannot be either true or false and should not therefore undermine our propositional account of the physical world in any significant sense.

� A completed physicalist psychology would require the inclusion of qualia in this way. It would require it to permit the mapping of the two aspects of human experience we are all familiar with to each other and to our propositional knowledge of the physical human organism. The two aspects in question being the inside observer�s perspective on the experience of being human, and the outside observer�s experience of the human organism in terms of the flesh, blood and brains view of the organism.

In short, there are good grounds for holding qualia to be a valid part of a total physical view and it is at least arguable that no significant problems are incurred if we decide to do so. There may be a consequent requirement that we must be able to determine the existence of distinct private events scientifically, but that is too large a topic to be handled in the current paper.

9.5 There is � or may be � a suggestion that the argument that leads to the perspective proposed here is circular. The case goes like this:

The perspective on the mind-body relationship proposed here is developed as a result of the Knowledge Argument. However, if the perspective is correct, then scientists with a complete physical view of the world would know about it, and would teach it to Mary in her black and white room, albeit in terms of black and white experiences rather than colour experiences. They would also know about the Knowledge Argument and would teach her about this also, as far as this was possible in a black and white room, showing her the difference in physical correlates in herself when seeing �red� in black and white and in others who are seeing red in the real world. Mary would still acquire colour experiences and learn something new on leaving the room, but she would already know that this new knowledge was not a threat to physicalism if the perspective on the qualia-physical relationship proposed in the present paper is correct. The question of whether or not Mary�s new knowledge refuted physicalism would not arise, so arguments leading to the perspective itself would not arise and neither would the perspective. The concern is that the argument for the perspective depends on the Knowledge Argument, but if the perspective is true, there is no Knowledge Argument and no argument in favour of the perspective.

In fact, there are two reasons why this concern is not justified:

� First, even in the scenario just described, Mary will still learn something new on leaving the room that is a potential threat to physicalism. It will still be true that this knowledge will refute physicalism unless it is knowledge that cannot be expressed verbally without loss. And it will also still be true that it will refute physicalism unless it is valid knowledge of the physical that is itself physical. Mary may know how to deal with the challenge to physicalism her new knowledge represents, but the challenge itself still exists. It is still true that if Mary learns something new then physicalism is refuted unless the perspective on the qualia-physical relationship presented in this paper (and, in this scenario, known to Mary in her room) is true. It is simply that if Mary already knows about the perspective that allows physicalism to stand then the process of stating the Knowledge Argument becomes more convoluted. In particular, it becomes necessary to spell out the perspective from the start, making the whole process of developing the argument in its favour somewhat less straightforward.

� Second, although the qualia-physical relationship presented here has been developed initially on the basis of an examination of the Knowledge Argument, the case for the perspective itself does not depend on the Knowledge Argument. The value of the Knowledge Argument is that describes readily imaginable circumstances tha