Blue Sky Thoughts E-Book

Jaime Carnie

• Herausgeber: Marion Boyars
• Kategorie: Geisteswissenschaft
• Sprache: Englisch
• Veröffentlichungsjahr: 2007

Beschreibung

With reference to drug-induced visions and the perceptual capacities of bees, Carnie deconstructs the work of Descartes, Newton and Berkeley to produce a new persepective on the way our senses operate.'All credit to him for building the case for an unfashionable theory, and making the reader think - which is what philosophy is supposed to do' Independent on Sunday. 'I like a writer with a big idea. This lucidly eccentric book offers pregnant evocations of dozing on the beach, or walking through a forest, arguments with Newton or Descartes, and musings on LSD trips...Interesting if true.' Stephen Poole, Guardian

Leseprobe

Blue Sky THOUGHTS

Colour, Consciousness and Reality

by Jamie Carnie

for Fiona

CONTENTS

Title Page

Dedication

Epigraph

INTRODUCTION

PART I: COLOUR UNCONFINED

1. Blue Sky Thoughts

2. Forest of the Senses

3. Descartes’ Perception Machine

4. Newton Against the Natural View

PART II: FROM COLOUR TO CONSCIOUSNESS

5. Mega-mind and Micro-mind

6. Mind and Body

PART III: COLOURS AS RELATIONS

7. Rescuing Direct Realism

8. Relational Colours: A New Entity

9. Sense Qualities as Relations

10. A Relational Theory of Sensory Qualities

11. Problems

12. Solutions

13. Colour and Newton’s Experiment

14. The Bending of Light

15. A Bee’s Eye View

16. Jewel in the Sky

17. The Colours of Space

PART IV: CONSCIOUSNESS (SOLVING THE HARD PROBLEM)

18. The Visual Opening

19. Sensory Memory

20. On Having No Mind

21. On Having No Mind-Body Problem

22. The Hard Problem of Reality

PART V: CONSEQUENCES

23. A World of Value

24. The Function of the Neuron

NOTES

BIBLIOGRAPHY

ACKNOWLEDGEMENTS

About the Author

Copyright

***

It is possible to say something true. For example: ‘something exists’. The truth of this statement cannot be doubted. It is uniquely certain because it is unquestionable that we as humans experience. It would be impossible for experience to occur and yet for absolutely nothing to exist.

But if we know with complete certainty that something exists the next question to be asked is, what is the nature of this existent ‘something’, or reality? Given that its existence is implied by experience it is likely that an answer to that question is best approached by ascertaining the nature of experience itself.

***

INTRODUCTION

Colour appears all around us. From the blue of the sky to the green which dominates the natural world, and the bewildering diversity of hues displayed by flowers, fruits and animals. What is common to all occurrences of colour, however, is that each individual instance is extremely simple. The field of red visual quality visible on the exterior of tomatoes, for example, does not contain any distinguishable elements or structure. One consequence of such simplicity is that the contrast between the appearances of different hues – red, green, blue, yellow and so on – is maximised, and the chromatic variety offered to us by the surfaces of the world is as great as it could possibly be. Another consequence is that colour provides one of the most basic forms of content contributing to the appearance of the world. The other forms of content that make up the appearance of the world are the remaining sensory qualities of sound, smell, taste and heat. These too are equally simple in nature. Thus individual occurrences of the aroma of baking bread or the sound of a firework exploding are – along with colour – as simple entities as one will ever encounter in the universe.

Yet despite their significance as providers of content, and their ubiquity, man has yet to achieve an understanding of the nature of the sensory qualities. This is remarkable given their simplicity. They hardly present the technical challenges of such ultra-complex objects as brains or galaxies, which contain billions of components (nerve cells and stars respectively). It is all the more extraordinary, too, in the present age, when scientists have developed their disciplines to the point of being able to explain events in the physical world at scales of structure ranging from the interior of the atom to the entirety of the cosmos. The position is somewhat analogous to that which notoriously obtains in the field of medicine regarding the ‘common cold’. Just as this most widespread and down-to-earth of afflictions remains incurable while treatments have been found for more esoteric diseases, so here the simplest features of the physical world, and those which have the most direct impact on man, remain a mystery while nature’s most complex structures are steadily being laid bare.

Of course, science has revealed a great deal about the events that usually occur in the material realm when sensory qualities become evident. Physics has told us about the nature of electromagnetic radiation (‘light’ as we call it when it vibrates at frequencies that our eyes can detect), which reflects off objects when they appear coloured, and radiates from them when they feel hot. It has also told us of sound waves that in a similar way are associated with the quality of sound. Chemistry has revealed the make-up of molecules which, when they diffuse through air, give rise to smells. But there is no prospect of the disciplines of science shedding any light on the mysterious nature of sensory qualities themselves – the blueness that we see in the sky, the sound of leaves heard rustling in the wind, or the warmth felt as given off by a crackling fire. This is precisely because of their simplicity and content-providing nature. For these characteristics make the sensory qualities quite unlike the types of entities that science is capable of dealing with.

In contrast to, say, atoms, which are made up of an internal structure of component particles such as electrons and protons, entities like the colour red and the smell of thyme possess no structure and hence have no measurable or quantitative features. As they are neither quantitative or measurable they cannot become subject to the mathematically-based (therefore quantitative) forms of theorising that prevail in science. For the same reason no instrument could ever be built that was able to detect the sensory qualities (as distinct from the signals such as light or sound waves, which are associated with them) so they could never be investigated through science’s experimental procedures. In short, the sensory qualities are invisible to everything in the scientist’s tool-kit. The combination of super-simplicity and content-provision that characterises the sensory qualities – often referred to by saying that colours, sounds and so on are ‘qualitative’ rather than quantitative – enables them to slip through science’s otherwise all-conquering ability to tease out the structures of reality.

If questions about the sensory qualities cannot be addressed by science then the techniques of philosophy may offer a more promising alternative. If and when philosophers ever manage to answer them, we can expect the answers to have implications both in the arena of the ‘external’ physical realm and in that of the ‘internal’ mental one. This is because perception, the activity in which awareness of sensory qualities invariably arises, acts as a bridge between these two domains. Inevitably, therefore, any consequences which will follow from our coming to understand the nature of the most basic entities to arise in perception, will fall on both sides of that bridge.

But it has to be said that advances in achieving a philosophical understanding of the nature of the sensory qualities have so far occurred at a less than impressive rate. In one form or another, the question of the nature of the sensory qualities has formed a topic of consideration by thinkers (in East and West) for many centuries. Yet even now there remains little or no sense of movement towards a complete solution. Why is progress so restricted? The reason for this, I suggest, is the same as the explanation for philosophy’s poor performance in answering many of the questions which confront it. The method used to create solutions to philosophical problems is non-repeatable. In consequence, the discipline is arguably still in its Stone Age.

If my experience is anything to go by, what philosophers do when confronted by a problem is to ‘sense out’ a solution to it. This is a lengthy and quasi-artistic procedure which is similar to how a painter or sculptor forms their work. It is also, no doubt, akin to the semi-intuitive procedure that would have been acquired, after years of practice, by Stone Age ‘knappers’ – who were, after all, the sculptors of their day – in order to strike a piece of flint in the correct way to fashion neolithic implements of utility.

In philosophy each new problem needs to be ‘sensed out’ from scratch, just as a Stone Age knapper faced with a fresh piece of raw flint would first have had to feel it all over before creatively applying his intuitive skills and working out at what angle and force to strike it. Because the methodology is intuitive and creative, for both the Stone Age worker and the philosopher, each new problem demands an approach which, although it may build on skills acquired in previous attempts, is unique to the particular problem being faced and is never repeated for others.

This is all quite different from what happens in science, which through its use of mathematics for the development of theorems and a standardised protocol for experimentation, is in possession of repeatable procedures that are applied again and again to every new problem that comes up. No-one would deny that there is also a significant element of creativity in science, but the foundation of its methodology – in contrast to that of philosophy – involves a set of procedures that are infinitely re-applicable to any problem that may be confronted. In this respect, extending to it the ‘pre-historical’ metaphor applied to philosophy, one may say that science is in its Bronze Age. Bronze Age metalworkers discovered how to combine a standardised ‘recipe’ of ingredients under heat to form bronze, and thereafter were able to repeat the same operation at will in order to produce metal ingots to order, just as scientists can repeat their standardised recipe of procedures at will in order to solve virtually any problem that may arise.

People react to the primeval position in which philosophy finds itself in different ways.

Amongst the tribe of philosophers one notices, for example, endeavours to emulate some of the superficial features of science’s success, such as attempts to apply methodologies which have a semi-scientific ring to them, or the finishing of texts to a high level of technical language. Reactions such as these are somewhat like members of the unruly tribe of philosophers jealously watching the metal swords and jewellery of the advanced tribe of the ‘Scientii’ in the neighbouring valley glitter in the sun, and taking to polishing their crude stone artefacts in a vain effort to achieve a similar effect.

Another possible reaction to the condition of philosophy could be to think that if the discipline is perhaps only in its Stone Age then realistically it stands little chance of answering any of the questions which confront it. But I would commend an alternative attitude to this which offers a more positive way of looking at the situation. If the possibility exists that philosophy is currently only in its Stone Age, then there may as yet be great tracts of discovery to be made and huge fields of development for the discipline to undergo in the future. After all, once it develops beyond its Stone Age, philosophy will presumably be as different from the subject we know today as chemistry currently is from alchemy. So on this view the possibilities offered by the present situation are considerable and there is a significant chance that there may genuinely be answers ‘out there’ to many of philosophy’s questions.

In this book it is this positive outlook, and the associated attitude that philosophical questions are in principle answerable, that I have attempted to bring to bear on the problem of the nature of the sensory qualities. In trying to find that answer I have endeavoured to strike a blow at the ‘flint’ of the problem at an angle that to the best of my knowledge has not been attempted before. Whether or not it succeeds in revealing a form of answer that carries any worth will be for others to judge.

PART I: COLOUR UNCONFINED

1. Blue Sky Thoughts

Imagine a beach. The steep path which you have been following over an arid hill top from the nearby fishing village, after a pleasant midday meal and a glass of wine at the local taverna, has reached the end of its course through parched shrubland that is richly scented by mint, laurel and myrtle, and sparsely broken by dried-out trees. From this elevated vantage point the shape and setting of the beach are now fully visible. It is a great golden arc of sand along the curve of a wide Mediterranean bay which separates grass-fringed dunes from an open vista of glistening sea, where waves roll in rhythmically and curl and break in the shallows. Along the belt of sand numerous bathers are scattered in groups, taking advantage of the powerful sun which beats down from an unbroken sky of inky, cerulean blue above. Two beach cafés nestled close in by the dunes are attracting custom by offering a refuge under their slatted bamboo roofs from the relentless heat, and a ready supply of cold drinks.

Upon leaving the slight shade afforded by the trees you instantly feel the full intensity of the heat. The sun burns strongly on your arms and face and, when you descend to the beach and remove your shoes, you find that the sand is almost painfully hot to walk on. But a neat line of indigo blue sun-loungers, each with its own pale turquoise sun-shade, forms a laddered gash of alternating colour and shade along the centre of the beach. Having checked in your pocket for the right number of euros needed to hire one, you walk across to the nearest and settle down on it, pulling out a thriller to read from your bag.

After twenty minutes of dozing and reading in the sun the attractions of indolence begin to wane and you sit up to examine your surroundings. The first thing that catches your interest is the sea and the sunlight which sparkles off its many wave crests like an army of distant flashlights. But the effect is tiring on your eyes, so soon you let your attention drift skywards to the visually more relaxing vista of boundless blue.

DEEP BLUE

During the next hour the peaceful sky becomes an ever more intriguing object of contemplation as the idea slowly develops that there is a unique character to its colour. This realisation is brought about by a subtle contrast between the coloured appearance of your sun shade and that of the sky. Looking directly upwards your field of vision is partially filled by a segment of the underside of the parasol. The sun-bleached turquoise of the umbrella’s material is slightly darkened by its own shadow and as a result its hue perfectly matches that of the sky, resulting in a single glorious expanse of blueness across the entirety of your visual field. Yet despite their identity of hue there is a marked difference between the appearances of the two visible regions of blue colour. That on the underside of the umbrella seems flat and surface-like, whereas that in the sky looks as though it is radiating downwards from a region high above in the atmosphere. The blueness of the sky has a quality of downward-pointing to it, and appears to reach out from its location in the sky, whereas the blue of the umbrella looks as if it is simply attached flat on the surface of the material like a two-dimensional field of colour that is integral to and wholly contained by the material.

This sets you to thinking about colour more generally. It is evident that most colours visible in the terrestrial environment have the appearance of two-dimensional or ‘flat’ surfaces more akin to the blue of the umbrella than that of the sky, because they reside – or at least appear to reside – on the exteriors of physical objects. At this point you look around seeking further examples. The red colour on the Stella Artois beer signs outside the beach cafés offers one. Another, you notice, is the lurid purple of the plastic plates being used by a nearby French family for their picnic. The appearance of these colours could be likened to fine coatings of redness and purpleness respectively on the external surfaces of the physical objects. But the azure of the sky is unlike such flat colours. It does not look like a blue coating on any kind of a surface high in the atmosphere. When you look upwards at the sky it doesn’t seem as though there is a surface up there on which the blueness might reside. And more than that, the blueness appears to project downwards from its location in the atmosphere in a way that no natural surface colour ever does. It is almost as if the sky is a great field of blue that is glowing downwards towards the earth. Furthermore there is, of course, no solid, physical surface in the sky to which the blueness could belong. So if the blueness of the sky is not a normal surface colour what is it? Could it be, the thought occurs, more like a translucent one which belongs to the entire volume of the atmosphere? After all, the colour of the sky is caused by the scattering of sunlight from the air molecules which make up the atmosphere,1 and there are many other such translucent colours in the natural world; colours that don’t occur merely on surfaces, but permeate through the volume of things.

At this moment you notice some refreshments which the father of the French family has prepared to accompany their picnic. In two glass tumblers he has poured first some cassis and then generous measures of white wine. The translucent, deep red colour of the resulting drinks of kir is not on the surface of each glass but extends throughout the volume of the liquid. If the blue of the sky is in the same way a feature of the entire volume of the atmosphere this would explain why no surface of blue is to be found when one looks up into the sky. It would also account for the sense of depth that one experiences in its appearance. But there remains still the fact that the colour of the sky manifests downwardly from its location. This would not in itself be explained by the possibility that the sky’s colour permeates the volume of the atmosphere like a translucent colour.

SPHERE OF LIGHT

You consider the enormous panel of unblemished blueness above as you absorb these ideas. Doing so your gaze briefly sweeps over the sun, now somewhat past its zenith. At that moment a new thought occurs. If the blue of the sky is not a surface colour then certainly the colour of the sun cannot be either. The sun is a distant globe of seething hot gas which we experience as yellow in colour. Yet its yellowness, just like the blue of the sky, is quite unlike any normal surface colour. This thought is reinforced when you notice two boys playing football. They are doing so with a bright, saffron yellow, plastic beach ball. If the sun’s yellow were like a ‘normal’ surface form of colour this, you realise, is how it would appear. The solar globe would look something like a giant yellow beach ball hanging in distant space. (Perhaps somewhat like a brighter version of the moon.) Yet in actuality the sun appears nothing like a yellow-coated sphere at all. Its yellow colour literally blazes out towards us from the solar body.

You lie back on the sun-lounger to assimilate further these unfamiliar new concepts. As you consider them it gradually becomes evident that a common feature distinguishes the colours of the sun and sky from other instances of colour. In both cases the differentiating factor is that they have the appearance of not being confined to their physical locations. Thus while surface and translucent colours appear to reside in a simple fashion on the surfaces or in the volumes defined by their ‘host’ objects, what is special about the blue of the sky and the yellow of the sun is that the same is not true. They appear to manifest outwardly from their source locations. The blueness of the sky does so downwardly from the atmosphere, and the yellowness of the sun does so outwardly through space from the substance of the solar globe.

BUBBLE OF SOUND

A few moments later there is a sudden and fleeting instant of coolness. You open your eyes to see that a tall man has just walked by. His shadow has passed over you and interrupted the warming rays of the sun. This brings to mind the fact that people experience not just the colour of the sun but also its heat. As you lie on the lounger feeling the intense rays rapidly warming you back up you mentally compare the form displayed by the sun’s qualities of heat and of colour. The sun’s quality of heat, you realise, is no more contained on its surface than is its colour. Just as colour is manifested outwardly from the solar globe so is heat. The sun’s quality of heat reaches out across space to be felt here on the beach, as does its colour.

You shut your eyes, intending to consider such parallels further, but a short while later the light sleep into which you unintentionally fall is interrupted by a gentle buzzing sound. It seems to be coming from the far end of the beach. Sitting up you scan the sky in that direction and eventually make out a small green triangle which is just visible in the distance, drifting towards you, high above the dunes. As the shape approaches over the next few minutes the volume of its sound gradually increases and the triangle soon resolves into the form of a microlight aircraft. The pilot circles the craft lazily over the beach a few times and while it is overhead you find yourself considering the noise that it produces. The high-pitched drone made by its straining two-stoke engine and the propeller biting into the air is not confined to the region of the craft. It does not give the appearance of there being a bubble of sound locked into the immediate space around the craft which travels along with it as it flies. Rather, the sound quality reaches out from the craft towards the surroundings in much the same way as the colour of the sky and of the sun manifest outwardly from them.

Sound it seems, displays the same characteristic of extending outwardly as colour and heat do. In fact, you note, in none of the cases considered so far has a quality been found to give the appearance of manifesting intrinsically within its object. Thus, neither the colour nor the heat of the sun appeared confined to its outer layer. The sound of an aircraft did not arise as a bubble of auditory quality around it, and the blue of the sky was not fixed on a mythical surface floating high in the atmosphere. Rather, all of these qualities have been found to manifest outwardly from their apparent locations in the physical world.

A little later you decide to take a stroll. You head towards the dunes and then along the back of the beach and across to one of the beach cafés. Here a chef has laid out the first of the day’s sardines on a steel rack above charcoal which glows red-hot, and has started grilling them along with a selection of vegetables. Together with a small crowd which has gathered at the bar you watch the process for a few minutes.

As you observe the sizzling ingredients you can’t help noticing that their aroma permeates outwards from the grill-rack to fill the space around the café. No matter what position along the bar you adopt as vantage point the same mouth-watering smell reaches out to it. It occurs to you that odour has the same characteristic of manifesting outwardly that colour, sound and heat do.

NOT SO SIMPLE

It seems natural to think of the elements of sensory experience – the sensory qualities of colour, sound, smell, heat and so on – as integral to and wholly confined within regions of the physical realm. But the observations here on the beach indicate that each of the sensory qualities manifests a degree of extending outwardly. This shows that any conception of the sensory qualities as limited to restricted regions of the world misses out a key feature of their nature. For a number of centuries the dominant intellectual view has been that sensory qualities are mental constructs, but even here the idea that sensory qualities do not extend outwardly has prevailed. This is exemplified in the tendency acquired in the modern world (perhaps because of its preponderance of man-made surfaces) for thinkers to characterise such mental sensory qualities as two-dimensional in nature. Thus at the opening of the 20th century leading British philosopher Bertrand Russell went so far as to account for sensory experience as being composed entirely of ‘patches’ of such elements.2 In more recent times the respected neurologist Antonio Damasio used the more sophisticated but nevertheless still ‘flat’ metaphor of a cinema screen when he posited that the sensing mind is like a ‘movie’ in the brain. He claimed that: ‘Qualia are the simple sensory qualities to be found in the blueness of the sky or the tone of sound produced by a cello, and the fundamental components of the images in the movie metaphor are thus made of qualia.’3

For both of these leading thinkers, then, the essential feature of human sensing which has been identified here on the beach is to be discounted. What man’s perceptual experience amounts to is simply a set of flat regions of sensory quality which come together as a shifting array in the forum of the mind, somewhat like the elements of a dynamic mosaic. From this array the mind formulates a picture of the three-dimensional world, much as the illusion of a view with depth can be derived from the two-dimensional areas of colour on a photograph or cinema screen. But the examples identified on the beach show such ideas to be overly simplistic. They indicate that sensory experience contains subtle features that crude pictures such as those of Russell and Damasio cannot account for. For on the beach we have seen that the sensory qualities of colour, sound, smell and heat all display a common characteristic of manifesting outwardly from their physical locations. Furthermore, another plausible conclusion that can be linked to our observations is that outward manifestation of sensory qualities is always associated with an appearance of directionality. Thus the blueness of the sky manifests itself in a downward direction, but it never, for example, manifests itself sideways across the atmosphere, nor upwards into space. Likewise, when observed from a distance the sound of a microlight emanates outwards from the aircraft but never inwards back to the craft. Apparent directionality and outward manifestation seem to be closely combined in most, and perhaps all, sensory qualities.

That there may be these twin characteristics universally amongst all sensory qualities can hardly be an insignificant matter. Could it be that there is more to understanding the sensory qualities than has been appreciated so far? In this book I will endeavour to explain that this is indeed the case. But more than that, I will argue that the difficulties presented by one of the hardest problems man currently faces in trying to understand the nature of consciousness – the question of how it arises from the physically nondescript grey-matter of the brain – are due to oversimplification of the nature of such sensory elements, in the manner of thinkers like Russell and Damasio. When the full and subtle nature of the sensory elements – as revealed in the blueness of the sky and other such phenomena – is properly taken into account, this allows the jigsaw of consciousness and its relation to the physical realm to be pieced together in a remarkably neat and altogether revolutionary fashion.

The issue of outward manifestation is not the only one concerning the sensory qualities that it will be necessary for us to examine in order to fully explore the nature of sensory consciousness, its relation to the physical matter of the brain and to the physical realm more generally. In addition we will have to address what is perhaps one of the most profound questions about the sensory qualities of all.

Notes

1. Light & Colour in the Open Air, Minnaert, pg. 239.

2. Mysticism and Logic, Bertrand Russell, pg. 140.

3. The Feeling of What Happens, Antonio Damasio, pg. 9.

2. Forest of the Senses

There is an old question, often attributed to Zen Buddhism, about whether a tree falling unheard in a remote forest makes a sound…

Imagine, therefore, a great wood of evergreens in the foothills of a high mountain range many kilometres from the nearest human habitation. In the depths of this endless forest one pine tree stands out taller than most. The tree is ancient and the time has come for it to yield its place to a new generation of saplings which are thrusting up into every available space in the tightly packed woodland. The tree’s great height is further accentuated because it rises from the crest of a ridge between two valleys.

The roots of the upstanding tree are old and decayed and they have been tested beyond endurance by an overnight gale which sent waves of turmoil through the wood like a field of wheat being ruffled in a breeze. Standing in its prominent position where it was exposed more than most to the tugging of the wind, the majestic pine now sways backwards and forwards as if undecided about its future. Then, a sudden slumping motion jolts it as its deepest roots give way, and at last the grand old pine pitches into space. The huge trunk arcs forward smoothly, while at its base its network of roots are snapped in quick-fire succession and tear a great mound of earth from the surrounding soil. The descending trunk smashes effortlessly through the foliage of nearby trees, snapping off even the thickest of their branches as if they were twigs. Upon impact with the ground a great judder is sent through the length of the trunk, causing it to rebound momentarily into the air, and vibrations emanate through the surrounding soil making the nearby vegetation shake in a wave of frantic trembling.

Yet the nearest human being to this crescendo of events is a farmer patiently tilling his fields beyond the edge of the forest a number of kilometres away. So it all plays out far beyond the range of human ears. The question which Zen Buddhism challenges us to answer is this: do such events occur with or without a quality of sound? Does the storm of physical events which make up the fall of the tree produce an apparent noise – despite being unheard – or does it all occur in utter silence, as in a silent movie?

Yet such a forest, so far from human beings, can also be the setting for many similar questions about the other sensory qualities. For example, consider a small clearing at the bottom of one of the valleys beyond the ridge where the tree has fallen. Here, amongst the berries, flowers and stones are occurrences of each of the other sensory qualities, all equally hidden from human awareness. For example, nestled amongst the undergrowth which makes up one side of the clearing, is a wild rose which is producing its first flowers of spring. The young petals reflect from the sunlight that is falling upon them a wavelength of light which we would call ‘pink’. But unseen by any human eye do the petals display this – or any – colour quality? The flowers are also emitting a fine gas of complex organic molecules, but in the absence of a human to detect their scent does this mean that the flowers are presenting a perfume to the world around them? Further along is a thicket of brambles laden with juicy blackberries that are ripening in the midday sun. Yet without being placed in a person’s mouth have they any sweetness? What about the bare outcrop of rock which protrudes from grass in the middle of the clearing? It has had the sun shining down upon it from overhead all morning. To the human touch the rock would feel, if not hot, then at least distinctly warm. But there are no humans here to touch it. Despite this, does the rock somehow present a quality of warmth to the nearby space?

THE SECRET LIFE OF THE SENSES

Along with the fallen pine tree, the questions posed by the clearing in the ‘forest of the senses’ illustrate a common point, which is that all of the sensory qualities are open to the same query: do they exist in the physical world in the absence of human perception? This is partly a straightforward question about whether such qualities can exist in a domain that is known to be made up of objective particles such as atoms and molecules. But also partly a not-so-straightforward question about how, if they do, they can make themselves manifest to an observer-free environment – is it possible for them to have some sort of ‘secret life of appearance’ all of their own?

A good way to get a picture of what this latter question means is to consider it when extended to an extreme situation. And what could be more extreme in terms of lacking observers than outer-space? Consider, therefore, the following extra-terrestrial example of sensory qualities without perceivers. It is offered by Beagle 2, the European Space Agency’s lander on Mars, which in 2003 attempted a descent to the planet’s surface from the ‘Mars Express’ spacecraft. Unfortunately, the likelihood is that the probe never made it intact to the surface because no data was ever returned from the vehicle once on the planet. However, its fate was not established with certainty and there remains the slim possibility that it may have endured the descent and subsequently experienced a communications fault once on Mars. This means that despite the expedition being a disaster from a scientific point of view, it may – if the vehicle survived – have unintentionally given rise to a philosophical triumph. For the Beagle 2 Lander had a unique feature. Bolted to its side was a small and colourful piece of artwork on a triangular slab of metal by the artist Damien Hirst.1 It was one of Hirst’s ‘spot paintings’, composed of dots of colour on a plain background (albeit at a size which could fit in the palm of a human hand, considerably smaller than was usual for his gallery pieces). It was not just an aesthetic gesture on the part of the Beagle team to invite Hirst to contribute a spot painting, for the work was to be used to help calibrate on board cameras and spectrometers. But whatever their motivation, if the vehicle did manage to survive its undoubtedly tricky landing, then for a period of time there may have existed in the lonely isolation of the boulder-strewn landscape of Mars (and perhaps even now still does) a small metal triangle covered in dots of differently coloured pigment which was bolted to the side of a battered and dust-coated little machine.

Mars is not only a place where no humans have ever been, scientists do not even know if there is life of any sort on the planet. So with Beagle 2 and Hirst’s spot painting we get the question of the secret life of colour in an historically extreme form. For if sensory qualities such as colour do exist in the physical realm without any dependence on human perception, then it may be the case that even now at a lonely spot some millions of kilometres from earth in the barren terrain of Mars the red, orange, green and blue colour qualities of Hirst’s spot painting are doing so. In which case they are manifesting as appearances to…well, to what? The answer cannot be that they are manifesting to any form of consciousness, because there is none on the planet of Mars. So it can only be that if the colours are manifesting at all they are doing so to the surrounding, entirely non-sentient locality. The colour qualities of Hirst’s little spot painting are appearing, if at all, to an environment which is devoid of even the slightest consciousness. More generally, it is a corollary of the idea that sensory qualities exist independently in the physical domain that they can manifest to environments that are entirely free of observers. There are many other examples of locations in the universe which illustrate the truth of this point, beyond the case of Beagle 2. From deep in unexplored ice crevasses here on earth to lava flows on the moons of Saturn, there are a multitude of locations in the cosmos which on the view that sensory qualities exist independently would have colour quality present but at any given moment are entirely free of sentient observers.

THE NATURAL VIEW

To return to the clearing in the ‘forest of the senses’. There are only two possible answers to the question of whether sensory qualities exist in the physical world without being perceived: either they do or they do not. Let us examine the implications of each of these two responses.

According to the first answer the way the world ‘looks’ (and sounds, smells and tastes) when we are not observing it is exactly the way that it does when we are. In the case of colour this can only be because the fields of visual quality which we call ‘colour’ are genuinely located on the surfaces (or in the volumes) of physical objects. In the case of the other sensory qualities it can only be because the regions of auditory and olfactory quality which we call ‘sound’ and ‘smell’ are actually located ‘out there’ in the spatial environment just as they appear to be. On this picture, a wild rose which is hidden from human eyes because of its location deep in a forest, is nevertheless pink because its colour quality is actually on (or perhaps in) the flesh of its petals. Equally, despite the lack of conscious beings on Mars, Hirst’s spot painting attached to Beagle 2 does, somewhat in vain, display its aesthetic glories of red, blue, green and so on because these colour qualities are actually on the surface of his painting. Likewise, a tree which falls in a remote forest makes a ‘sound’ because the auditory quality which it generates is physically located in the surrounding space. Anyone wishing to accept this view has to be prepared to accept also, as we have seen, the somewhat unfamiliar position that such non-dependent sensory qualities manifest to the observer-free environment (in the sense of simply the inert space of the surrounding physical world).

But the second answer to the question posed by the forest of the senses leads to a very different view. Proponents of this alternative way of thinking maintain that sensory qualities can have no existence independent of our perception of them. The simplest and most obvious way in which this might be the case is if they are mental entities. There are good grounds for thinking this to be so. Colours, sounds, smells and other sensory qualities share a number of characteristics, such as simplicity and experiential directness, with bodily sensations like pain and tickles which are widely held to be mental. Also, of course, we can experience colours and the other sensory qualities, or at least residual versions of them, in purely mental arenas such as those of the imagination and dreams. According to such a picture, then, all of the physical events in the forest of the senses that we have been considering are unaccompanied by sensory qualities because there are no perceivers within the forest to give rise to them. On this interpretation, the forest becomes literally a realm without appearance. Likewise the spot-painting on Beagle 2 consists only of a block of metal with some daubs of pigmented chemicals. It displays no colour qualities to the Martian environment because none exist intrinsically on its surface.

It would be wrong to claim that anyone thinks the truth of either of these two pictures is a matter of common-sense, but it is the case that the idea of sensory qualities as existing independently and objectively within the physical arena is the one that most people (of all cultures) actually live according to and take for granted in their daily lives. Thus for example, at the simplest level, we all believe that, and behave as if, the colour qualities of things persist when we shut our eyes. Likewise, when an item such as a can of baked beans is placed out of sight in a well-lit cupboard no-one questions that its label retains its famous ‘57 varieties’ blue colour. Few of us even doubt that the beans inside the can, sealed off as they are from all light, retain their orange colour. In a similar way, most people would consider that, despite being unheard, a china plate falling to the floor in their house while they were out would produce a quality of sound – and a loud one – when it shattered to pieces. Our beliefs concerning the sensory quality of heat are of a similar nature, as shown by our attitudes to the heating elements of electric fires and cookers. For example, most people consider that when switched on these continue to give off an intense quality of heat, along with a dangerous amount of energy, even when they are not actively being felt.

The package of ideas centred on the view that the sensory qualities exist ‘out there’, independently of man, agrees so powerfully with the way that things appear in the world that it seems in many respects as though it ‘must obviously’ be correct. For this reason – and also because it accords with the practice of most peoples’ lives – I will call it the ‘natural view’ of the sensory qualities.