2. The Emergence of the Concept of Consciousness

2.1 Naive Realism

I am immersed in a colourful moving noisy tasty smelly painful spatially and temporally extended stream of things. During a nuclear explosion I see a grey mushroom cloud, hear a detonation, feel heat, touch wind and taste synthetic strawberry bubblegum in my mouth. I do not infer the presence of these things—they are just there before me as the world at this place and time seen from my perspective.

When Cro-Magnon man peered out of his cave he saw a bright pattern of green leaves, heard a river and tasted sweet-tart berries in his mouth. The green of the leaves was present to him, framing the entrance to his cave, just as the river was crashing and roaring to his left. No complicated theories about consciousness troubled Cro-Magnon man: the world was simply present to him. In this idealised naive and simple time people simply saw the world, unclouded by theories of perception.

When a child opens its eyes it does not see a collection of qualia1 or conscious representations: just a red balloon ascending into the warm summer sky.

Most modern adults most of the time have a direct relationship with the world around them. We are immersed in a world of colourful moving noisy tasty smelly things. As we slog through our workaday lives we are not philosophizing—the blue of my computer screen is the colour of an object in the world; the tinny speaker sound is part of the world. We go outside and see cold grey skies and are lashed by cold lashing rain.

For me at least, the colourful cheerful world is the most important thing there is. I long to drink in more of the visible audible tasty moving world. What I hope for in any afterlife is that some kind of a world will continue, ideally in a reasonably pleasant way. While one can make abstract ethical points about the value of life, its real value for me is this immersion in a sensuous world.

This relationship with the world is often called naive realism: an interpretation of perception in which we directly see the world and the world is as we see it. However, there is nothing naive or realistic in our everyday encounters with the world—‘naive realism’ is a convenient label that we use to contrast our everyday immersion in the world with other theories of perception.

I am standing in my sitting room staring dully through dirty net curtains at nothing in the street outside. I cannot see the body of my aunt. It is out there in the garage. I walk into the garage and open the blue plastic sack. Now I can see the body of my aunt.

When I look at my aunt’s body it appears as three-dimensional, although I can only see part of it at one time. From one perspective I can see my aunt’s grey lips and clouded eyes, but I cannot see her whole head or body. I have to move relative to her body to see her thin grey hair and the matted dried blood on the back of her head.

My aunt’s body changes independently of my interactions with it. Each time I return to the garage I observe subtle changes in colour as her body decays. Her body has an objective existence that can be systematically probed in different ways. I can perform chemical tests; I can measure its hardness and weight.

Other people cannot see the body of my aunt. The police cannot see it. Uncle Henry, on holiday in Tahiti, is staring at the gyrating buttocks of a young woman in a grass skirt. He is not looking at the body of my aunt.

Naive realism is not simultaneous and all-embracing access to every object in existence. We see a small number of the world’s objects from one perspective. Objects have an independent existence that enables them to be perceived by other people. Different people see different things. We can perceive the same object on multiple occasions. Objects can be in different states at different times.

In our naively realistic encounters with the world we use the language of perception to indicate those things and those aspects of things that are present to us and to acknowledge that objects continue to exist when they are not being perceived. Instead of saying that my aunt’s body is there, I talk about perceiving my aunt’s body to indicate that it is currently present to me. Uncle Henry is not perceiving her body: it is not present to him in Tahiti.

Perception is similar to a bubble that we ‘carry around’ with us that contains the objects that are currently present to us. I will call this a bubble of perception. We are immersed in our bubbles of perception. When an object appears in my bubble of perception I see it from a perspective that is centred on my body.2

A visual representation of a bubble of perception is shown in Figure 2.1b. This is inaccurate because it shows the person’s body from a third-person perspective, whereas we experience our bubbles of perception from the inside—we look out from our bodies onto the world. This illustration has the further limitation that it only shows the visual aspect of a bubble of perception. Bubbles of perception also include tastes, sounds, smells, body sensations and emotional states.

In naive realism objects have the properties that we perceive them to have. The plastic sack is blue; my aunt’s body is cold; her clothes have a mothball and urine odour. Objects have these properties independently of whether they are inside or outside a bubble of perception. The plastic sack continues to be blue when it is in the garage and not being perceived by anyone (Figure 2.1a).

I sit in the kitchen and imagine my aunt’s body in the garage. Now the contents of the sack are fleeting and unstable, colours are washed out and the smell of moth balls and urine is not present. I dream of my aunt’s body. This is more vivid than imagination, but my aunt’s face changes from moment to moment, and it is difficult to inspect details and maintain consistency over time. I go for a walk in the forest and eat a mushroom. One hour later my aunt rises from the ground before me: her eyes are dark geometric spirals; her hair is a writhing mass of white maggots.

Figure 2.1. Visual representation of a bubble of perception. a) Domestic scene. In naive realism the sack in the garage continues to be blue when no-one is looking at it. b) A visual representation of a bubble of perception. This uses a third-person perspective to represent our sense of inhabiting a body and looking out at a world. Although this is substantially different from an actual bubble of perception, which we experience from inside our bodies, it is the best way that I have found of depicting a bubble of perception. Image © David Gamez, CC BY 4.0.

We no longer believe that imagined, dreamt or hallucinated objects are objectively present in a second spiritual world. It no longer makes sense to say that we perceive imagined, dreamt or hallucinated objects. This is particularly true now that perception is associated with theories about electromagnetic waves, sound vibrations, and so on. To address this issue I will replace ‘bubble of perception’ with the more inclusive term ‘bubble of experience’, and distinguish between two types of bubble of experience:

• Online bubbles of experience are connected to the world: their states change in response to changes in the world and detailed information about the world can be accessed on demand. They typically have vivid colours, clear sounds, strong odours and intense body sensations. In an online bubble of experience objects are stable, we can view the same object on multiple occasions and people generally agree on an object’s properties. We are immersed in online bubbles of experience when we perceive and interact with the world.
• Offline bubbles of experience are not connected to the current environment, although they might correspond to past or future states. They are often unstable, low resolution and low intensity. Colours are washed out; smells, tastes and body sensations are rarely present. Offline bubbles of experience are typically weakly perceptual—we cannot interact with objects in a systematic way, and it can be difficult to repeatedly view the same object from multiple perspectives or to examine small details. People typically do not agree about the objects that they encounter in offline bubbles of experience. We are immersed in offline bubbles of experience when we dream, remember, hallucinate and imagine.

A bubble of experience can have a mixture of online and offline contents. When I hallucinated my aunt the forest was an online component of my bubble of experience; the aunt and maggots were offline.3

2.2 Invisible Explanations

The flowers in my living room appear in my online bubble of experience on multiple occasions. I can see them from multiple perspectives and uncover more of their properties. They appear in other people’s bubbles of experience. The flowers are part of an independent world, which is often called the physical world.

The physical world has regularities. If I throw a pig out of a window, its pink colour and screams move together and its rate of acceleration can be calculated using a simple equation. If I mix one part glycerine with three parts nitric acid, I obtain an explosive mixture that can alleviate angina.

We explain these regularities by postulating the existence of invisible objects and properties in the physical world. These do not appear in our bubbles of experience—we believe in their existence because they improve our ability to make predictions about objects in our bubbles of experience.

X-rays are invisible waves that were posited to explain the appearance of patterns on photographic plates. These patterns can easily be explained if there is a form of radiation that cannot be perceived with the human eye. Our belief in X-rays was strengthened by the development of other methods for detecting them. Only the effects of X-rays appear in our bubbles of experience—the rays themselves are invisible.

Visible and invisible gods are often used to explain regularities in our bubbles of experience. A statue of Tlaloc might be considered to be Tlaloc himself, something that Tlaloc inhabits to some extent or just a representation of Tlaloc. Sometimes the Judeo-Christian god is depicted as a beardy bloke floating in the clouds; more often he is assumed to be invisible.

Prayers, sacrifices and moral rectitude encourage the gods to bestow rain, fertility and a good harvest on their virtuous subjects (see Figure 2.2). Murder, incest and eating prawns anger the gods, who inflict earthquakes, floods and infertility on people who stray from the path of righteousness.

Figure 2.2. The presence of an invisible god explains regularities in the visible world. a) Worshippers of Tlaloc offer up sacrifices and prayers for rain. b) The psychology and actions of the invisible god explain the appearance of the rain. Image © David Gamez, CC BY.

Early astronomers explained the regular movements of the heavenly bodies by claiming that they are embedded in concentric crystalline spheres. These spheres were invisible to human observers on Earth, but they probably believed that they could have touched them if they could have reached them.

Newton explained the movements of the heavenly bodies by claiming that they exert an invisible gravitational force on each other, whose strength is given by a simple equation. Newton could not explain how masses attract each other at a distance—at best he could point to magnetism as an example of a similar force. However, the invisible gravitational force, along with the equations describing it, made good predictions about the movements of the heavenly bodies, and so it became an accepted part of the physical world. While we can observe the effects of gravity in our bubbles of experience—a feeling of heaviness, movement of objects towards the Earth—gravity itself is invisible.

The ancient atomists hypothesized that the world is composed of invisible entities called atoms. They used the movements, swerves and interactions of the atoms to explain the visible properties of the world.4 This view was revived in the seventeenth century and later used to explain phenomena, such as the pressure and temperature of a gas. Although our theories about elementary particles have been substantially revised, atomism continues to play an important role in our understanding of the physical world.

Atoms and their constituent particles are invisible explanations because they never directly appear in our bubbles of experience. An atom might emit an electromagnetic wave that leads to an experience of red, but we experience the red, not the atom itself. We can generate pictures of atoms using a scanning tunnelling microscope, but these are the result of a complex technological process—not a direct view of the atoms themselves.

Our modern invisible explanations have become increasingly abstract. We now use complex mathematical equations to describe the behaviour of wave-particles and highly folded fields. These invisible explanations can be used to make accurate predictions about the behaviour of objects in our bubbles of experience.

Invisible physical explanations are extremely important to us. For non-religious people the physical world is all there is: a complete understanding of it would be a complete understanding of everything.

Whichever invisible explanations you accept, their common factor is that they are, by definition, invisible. They are hypotheses that go beyond our experiences in order to explain and make sense of our experiences. The effects of invisible entities appear in our bubbles of experience, never the invisible entities themselves.

2.3 Primary and Secondary Qualities

The particular bulk, number, figure, and motion of the parts of fire, or snow, are really in them, whether anyone’s senses perceive them or no: and therefore they may be called real qualities, because they really exist in those bodies. But light, heat, whiteness, or coldness, are no more really in them, than sickness or pain is in manna. Take away the sensation of them; let not the eyes see light, or colours, nor the ears hear sounds; let the palate not taste, nor the nose smell, and all colours, tastes, odours, and sounds as they are such particular ideas, vanish and cease, and are reduced to their causes, i.e. bulk, figure, and motion of parts.

John Locke, An Essay Concerning Human Understanding5

Some honey is in my bubble of experience. It feels warm and sticky. It is a dark semi-translucent brown colour. I taste the honey—it is sweet. I put the honey in a box and close the lid. Although the honey is no longer in my bubble of experience, it is natural to assume that it continues to be sweet, warm, sticky, and semi-translucent dark brown in colour.

I pass the honey to Zampano. He tastes the honey. ‘Cor blimey stab me vitals,’ he says, ‘that’s some bitter honey.’ In his bubble of experience the honey is bitter. So is the honey sweet, bitter, both sweet and bitter, or neither when it is outside our bubbles of experience?6

The honey changes colour when I put it in different contexts and expose it to light of different colours (see Figure 2.3). What is the colour of the honey in and of itself? What is the colour of the honey when it is outside my bubble of experience? When it is in the dark? When it is viewed by a snake?

Figure 2.3. Colour illusion. The jars of honey are identical; the shaded background makes the top jar appear to be darker in colour. Image © David Gamez, CC BY 4.0.

These contradictions in an object’s properties can be resolved by an account of perception that attributes some properties to the physical world and other properties to the interaction between the physical world and the senses. A good example of this approach is Galileo’s and Locke’s distinction between primary and secondary qualities.7 Primary qualities, such as size, shape and movement, are properties of the objects themselves. Secondary qualities, such as colour, smell and sound, arise when the physical world interacts with the senses—they are not properties of physical objects.

The size, shape and movement of honey are primary qualities: properties that honey has regardless of whether it is perceived or not. These properties are intrinsic to all physical objects. The colour and sweetness of honey are secondary qualities that arise when honey interacts with a person’s senses. When honey is outside all bubbles of experience it is not sweet, bitter or coloured in any way.

Different bodies have different sense organs and interact in different ways with their environment. This explains how the same physical object can produce different secondary qualities in different people. When honey interacts with my senses it produces sensations of warmth, sweetness and a dark semi-translucent brown colour. When it interacts with Zampano’s senses it produces coldness, bitterness and a dark semi-translucent orange colour. This account of perception avoids the attribution of contradictory properties to the same physical object. It explains how honey can be perceived as sweet by some people and as bitter by others; why the same patch has different colours in different contexts.8

The distinction between primary and secondary qualities was developed in response to the revival of atomism in the seventeenth century. Atoms were hypothesized to be the fundamental constituents of the physical world and primary qualities were properties of the atoms. Interactions between atoms in the environment and atoms in our bodies led to the appearance of secondary qualities, such as redness and sweetness (see Figure 2.4).

Locke believed that the primary qualities in our bubbles of experience resemble primary qualities in the physical world:

[…] the ideas of primary qualities of bodies, are resemblances of them, and their patterns do really exist in the bodies themselves; but the ideas, produced in us by these secondary qualities, have no resemblance of them at all. There is nothing like our ideas, existing in the bodies themselves. They are in the bodies, we denominate from them, only a power to produce those sensations in us: and what is sweet, blue or warm in idea, is but the certain bulk, figure and motion of the insensible parts in the bodies themselves […]9

When I am hugging a moving medium-sized bear in my online bubble of experience there is a moving medium-sized bear in the physical world. According to Locke the size, shape and motion of the bear in my bubble of experience match the size, shape and motion of the bear in the physical world. However, there is no growling sound, brown colour or pungent bear-smell in the physical world. Air vibrations, electromagnetic waves and molecules in the physical world interact with my sense organs to produce the growling sound, brown colour, and pungent bear-smell in my bubble of experience.

The primary qualities of physical objects are perceived through their secondary qualities. We cannot discover the size, shape or motion of an object without perceiving its colour, hearing its sound or touching it. Objects might possess their primary qualities independently of our perception of them, but these primary qualities can only appear in our bubbles of experience when they are clothed in secondary qualities. Physical objects are completely invisible without secondary qualities.

Figure 2.4. Primary and secondary qualities. The physical world consists of atoms with primary qualities, such as size, movement and shape. When atoms interact with a person’s sense organs they give rise to secondary qualities, such as colour, smell, taste and warmth, that appear in their bubble of experience. Image © David Gamez, CC BY 4.0.

2.4 Bubbles of Experience and the Brain

When I hit my head my bubble of experience is filled with bright points of light. Stimulation of my brain with electrodes evokes visual, auditory and somatic sensations. Brain damage damages my bubble of experience. My experiences can be altered by changing my brain’s chemical state.

The link between my bubble of experience and my brain is not logically necessary—it would not be a contradiction if a blow to my liver produced bright points of light. However, in this world, with these laws of nature, the strong correlations between my bubble of experience and my brain suggest that without my brain I would not have a bubble of experience at all.

Some people believe that bubbles of experience are linked to spatiotemporal patterns that are distributed across the brain, body and environment.10 This can be broken down into two claims:

1. Offline bubbles of experience are linked to spatiotemporal patterns in the brain, body and environment.
2. Rich vivid stable bubbles of experience are linked to spatiotemporal patterns in the brain, body and environment.

Offline bubbles of experience occur when there is little or no interaction between the brain, body and environment. This suggests that the first claim is false and offline bubbles of experience are solely linked with brain states. The second claim is difficult to test because rich vivid stable bubbles of experience typically occur when a brain is interacting with its environment (when a bubble of experience is online). However, given everything that we know about the brain, I believe that it is more reasonable and economical to assume that all bubbles of experience are linked with brain activity alone.11 This assumption cannot be proved at the present time, and it should be revised if it can be shown that a body and environment are essential for rich vivid stable bubbles of experience.12

When we are immersed in an online bubble of experience our bodies are interacting with our environment and our sense organs are passing streams of spikes13 down our nerves and changing the states of our brains (see Figure 2.5). When we are immersed in an offline bubble of experience the states of our brains are changing independently of our body and environment. In both cases I will assume that our bubbles of experience are only linked with states of our brains.

Figure 2.5. The relationship between a bubble of experience and a brain. I have assumed that the brain is the only part of the body that is linked to a bubble of experience. Signals from the world interact with the sense organs, which send streams of spikes down the nerves to the brain. The resulting brain state is linked with a bubble of experience. Image © David Gamez, CC BY 4.0.

In the previous section it was suggested that primary qualities are perceived through secondary qualities and that the primary qualities in an online bubble of experience directly correspond to primary qualities in the world. The pungent bear-smell did not exist in the physical world; the size, shape and movement of the bear in my bubble of experience matched or resembled the size, shape and movement of the physical bear.

Modern science has interposed the brain between bubbles of experience and objects in the physical world. Our experiences of size, shape and movement are now thought to be linked to firing patterns in populations of neurons. Now there is no direct connection between bubbles of experience and the physical world. Why, then, should we assume that primary qualities in our bubbles of experience resemble primary qualities in the physical world? Why should we believe that space and time in our bubbles of experience resemble space and time in the physical world?14

A computer is driving a car. Its memory consists of voltages that are updated by cameras, lasers and GPS. As the information in the sensors changes the voltage patterns change, and the program uses this information to calculate signals that are sent to control the brakes, accelerator, gears and steering. The computer’s voltage patterns are connected to the environment through the sensors, but they do not resemble the environment. The voltage pattern that encodes the shape of the road does not curve and it is not the same size as the road. The motion of the car is held as a single voltage pattern that does not move like the car and only changes when the measured velocity changes.

Back in Locke’s day the physical world was believed to be composed of atoms, which were easy to imagine as tiny bouncing grey spheres. It was natural to assume that the physical world was just like the perceived world, except for the secondary qualities, which were added by the process of perception. The motion, size and shape of the objects were identical to the motion, size and shape of our experiences of the objects—we were indeed seeing the things themselves.

Today the physical world has become unimaginable. We cannot imagine what a wave-particle or a ten-dimensional superstring is like. We have lost all reasons for believing in resemblance between our bubbles of experience and the physical world. We have no grounds for attributing either the primary or the secondary qualities of our bubbles of experience to the invisible world described by modern physics.15

We cannot prove that a physical bear is not identical to the appearance of a bear in a bubble of experience. And we have little reason to believe that a physical bear does resemble a bear in a bubble of experience. We just don’t know and cannot know. We cannot reach beyond our senses to see the physical world as it is in itself. We have to suspend judgment about what the physical world is really like.16

Figure 2.6. Interpretation of physical objects as black boxes. We have to suspend judgement about the appearance of the physical flowers and treat them as a black box that is a source of electromagnetic waves, molecules and mechanical stimulation. These signals stimulate the sense organs, which pass streams of spikes along nerves to the brain. The resulting brain activity is linked with a bubble of experience in which coloured, smelly, tasty, spatially and temporally extended flowers appear. Image © David Gamez, CC BY 4.0.17

As far as we are concerned physical objects are black boxes that interact with each other in accordance with the laws of physics. They are also sources of signals that enter our senses and are processed into spiking patterns that are sent along nerves to our physical brains, where they are transformed into more spiking patterns, which have some kind of connection with bubbles of experience that contain the coloured warm smelly faces of the people we love (see Figure 2.6). Russell makes this point well:

Modern physics, therefore, reduces matter to a set of events which proceed outward from a centre. If there is something further in the centre itself, we cannot know about it, and it is irrelevant to physics. […] Physics is mathematical, not because we know so much about the physical world, but because we know so little: it is only its mathematical properties that we can discover. For the rest, our knowledge is negative. In places where there are no eyes or ears or brains there are no colours or sounds, but there are events having certain characteristics which lead them to cause colours and sounds in places where there are eyes, ears and brains. We cannot find out what the world looks like from a place where there is nobody, because if we go to look there will be somebody there; the attempt is as hopeless as trying to jump on one’s own shadow.18

You are holding a brain in your hands: it is soft, warm and slightly sticky with blood. You lick it. It tastes of blood. You smell it—a humid, fresh, slightly meaty smell. It is reddish grey in colour. You drop it onto a marble worktop—a thwacking splat of sound. It has a size and a convoluted texture. It moves when slapped or thrown through the air. This is how the brain appears in your bubble of experience.

Now remove the properties that appeared when the brain interacted with your senses. Now the brain is colourless, silent, odourless; it is neither warm nor cold, neither soft nor hard; in fact it has no perceptible properties at all. Drop the illusion that the motion, size, shape, and spatiotemporal properties of the physical brain are preserved unchanged in your bubble of experience. All of these properties are transformed beyond all recognition by the neural encoding process. The physical brain vanishes: it can no longer appear as it is in itself in your bubble of experience. As far as you are concerned, physical brains are black boxes, just like every other object in the physical world. This is illustrated in Figure 2.7.

Figure 2.7. The relationship between a bubble of experience and an invisible physical brain. As far as we are concerned all objects in the physical world, including our bodies and brains, are black boxes. The arrows show the interactions between these objects in accordance with the laws of physics. Objects in the environment are sources of signals that lead to brain activity that has some kind of connection with a bubble of experience. Image © David Gamez, CC BY 4.0.

2.5 The Emergence of the Concept of Consciousness

I look to the right and see a dirty grey wall. I look to the left and see a black lamppost with scratches and flaking paint. Ahead of me a decrepit old man hobbles along a derelict street. I am awake, not dead, but consciousness is not present anywhere—there is no consciousness in the man’s stained trousers, no consciousness in the dirt, no consciousness in the smell of dog piss. Nor does consciousness appear when I turn my attention to my ulcerating stomach and painful feet. Consciousness is completely absent from my bubble of experience as I view the street. My reports are not driven by a thing or property called consciousness. I can describe everything without mentioning consciousness once.

Within naive realism there is no need for a concept of consciousness. People perceive different things with different levels of clarity and have different levels of wakefulness. Primary and secondary qualities are properties of the objects themselves, which they possess independently of whether they are being perceived.

The scientific revolution revived atomic theories and led to an unimaginable world of superstrings and wave-particles. As our physics developed, the objects that we encountered in naive realism were stripped of their colours, sounds, tastes and smells and sank into an invisible physical world. A tree ceased to be a tree—it became a colourless collection of jigging atoms, a probability distribution of wave-particles.

Physical trees became black box sources of signals; green trees continued to creak and sway in our bubbles of experience. We attempted to explain them away, and yet there they were in front of us with properties that could not be neatly shoehorned into the world of physics. We had to find a way of grouping, describing and explaining the colourful, smelly, noisy properties that were originally attributed to objects in naive realism.

We solved this problem by inventing the modern concept of consciousness. ‘Consciousness’ became a name for bubbles of experience, which were reinterpreted in relation to an invisible physical world. This is formally stated as follows:19

D1. Consciousness is another name for bubbles of experience. A state of a consciousness is a state of a bubble of experience.20 Consciousness includes all of the properties that were removed from the physical world as scientists developed our modern invisible explanations.

Initially the modern concept of consciousness emerged in response to the renaissance of atomism. In the seventeenth century the physical world was believed to only have primary qualities—secondary qualities were excluded from this world and developed a separate existence of their own that demanded an explanation. The solution was to package up secondary qualities with the concepts of mind, thinking substance and consciousness. This interpretation of consciousness is nicely summarized by Galileo:

Now I say that whenever I conceive any material or corporeal substance, I immediately feel the need to think of it as bounded, and as having this or that shape; as being large or small in relation to other things, and in some specific place at any given time; as being in motion or at rest; as touching or not touching some other body; and as being one in number, or few, or many. From these conditions I cannot separate such a substance by any stretch of my imagination. But that it must be white or red, bitter or sweet, noisy or silent, and of sweet or foul odour, my mind does not feel compelled to bring in as necessary accompaniments. Without the senses as our guides, reason or imagination unaided would probably never arrive at qualities like these. Hence I think that tastes, odours, colors, and so on are no more than mere names so far as the object in which we place them is concerned, and that they reside only in the consciousness. Hence if the living creature were removed, all these qualities would be wiped away and annihilated. But since we have imposed on them special names, distinct from those of the other and real qualities mentioned previously, we wish to believe that they really exist as different from those.21

The twentieth century developed the concept of consciousness to its logical conclusion. Our theories about the physical world became mathematical and abstract—they make beautiful predictions, but they are no longer based on the everyday properties and objects that we encounter in our bubbles of experience. The twentieth century also developed theories about how bubbles of experience are linked to the brain. This eliminated our reasons for believing that primary qualities in our bubbles of experience resemble primary qualities in the physical world. While physics is perceived to be the true or ultimate reality, we continue to be immersed in bubbles of experience in our daily lives: our need to express and address this issue led to the modern concept of consciousness. This trajectory from naive realism to twentieth century science and consciousness is illustrated in Figure 2.8.

The contents of a person’s consciousness are the objects and properties in their bubble of experience. When a burning bush is in my bubble of experience, the colour, smell, taste, heat and sound of the burning bush are the contents of my consciousness. When I say ‘I am conscious of hissing sap and orange flames,’ I am stating that hissing sap and orange flames are in my bubble of experience.

Figure 2.8. The emergence of the concept of consciousness. a) Naive realism. Objects have the properties that they are perceived to have and continue to have these properties when they are not being perceived. b) Naive realism is supplemented with a theory of perception, which I described using the idea of a bubble of perception. This was reinterpreted as a bubble of experience to handle dreams, hallucinations, etc. c) The revival of atomism in the seventeenth century led to a distinction between primary qualities, which are properties of physical objects, and secondary qualities that arise when the physical world interacts with the senses. The concept of consciousness was invented to accommodate the secondary qualities that were excluded from the physical world. d) Twentieth century science eliminates all resemblance between bubbles of experience and the physical world. Everything in our bubbles of experience is interpreted as consciousness. Image © David Gamez, CC BY 4.0.

Many consciousness experiments are based on the idea that a person has a particular level of consciousness. A person’s overall level of consciousness can be defined as the average intensity of the contents of their bubble of experience.22 A high intensity, vivid, stable bubble of experience with high resolution is consciousness at a high level. A bubble of experience that contains a few faint and unstable objects is consciousness at a low level. We say that Zampano is conscious when his physical brain is associated with a bubble of experience that has non-zero intensity.23 We say that Zampano is unconscious when his physical brain is not associated with a bubble of experience.

The distinction between online and offline bubbles of experience can be expressed in terms of online and offline conscious contents:24

• Online conscious contents are linked to states of the environment and are updated in response to changes in the environment. The environment is functionally connected to online conscious contents.25
• Offline conscious contents are independent of the environment. There is no functional connection between the current environment and offline conscious contents.

Consciousness can contain a mixture of online and offline contents. When I worship at the tombs of my ancestors the shadowy form of my grandfather rises from his grave, winks and raises his hat. My grandfather and his hat are offline conscious contents; the tombs and surrounding graveyard are online conscious contents.26

A suggestive piece of evidence for a link between the rise of science and the emergence of the concept of consciousness is Wilkes’ observation that there was no word for consciousness in the English language prior to the seventeenth century or in ancient Greek or Chinese:

Two intriguing facts. First, the terms ‘mind’ and ‘conscious(ness)’ are notoriously difficult to translate into some other languages. Second, in English (and other European languages) one of these terms—‘conscious’ and its cognates—is in its present range of senses scarcely three centuries old. […] In ancient Greek there is nothing corresponding to either ‘mind’ or ‘consciousness’ […] In Chinese, there are considerable problems in capturing ‘conscious(ness)’. And in Croatian, ‘mind’ poses interesting difficulties.27

There are contexts in which our modern English word for consciousness can be translated into ancient Greek or Chinese—for example, by ‘psyche’, ‘Sophia’, ‘nous’, ‘metanoia’ or ‘aesthesis’ in ancient Greek, or by ‘yìshì’ in Chinese. However, Wilkes claims that there is no generally adequate translation that captures our current use of ‘consciousness’.

According to Wilkes, this linguistic data shows that the modern concept of consciousness covers a number of disparate phenomena:

• Whether someone is awake or asleep.
• Body sensations, such as itches and pains.
• Sensory experience—for example, colours, tastes and smells.
• Ascription of propositional attitudes, such as deliberating, pondering, desiring and believing.

This leads Wilkes to conclude that consciousness is unlikely to be a natural kind or something that we can study scientifically:

Essentially, I am trying to say two distinguishable things. First, that in all the contexts in which it tends to be deployed, the term ‘conscious’ and its cognates are, for scientific purposes, both unhelpful and unnecessary. The assorted domains of research, so crudely indicated by the ordinary language term, can and should be carved up into taxonomies that cross-classify those which emphasis on ‘consciousness’ would suggest. Second, that we have little if any reason to suppose that these various domains have anything interesting in common: that is, consciousness will not just be a (cluster) natural kind.28

However, Wilkes’ observations about ‘consciousness’ can be interpreted to support the idea that consciousness is a modern name for a bubble of experience. Bubbles of experience are natural kinds that are common to all people speaking all languages. We all see red objects, feel heat, smell flowers and taste meat. However, scientific theories about an invisible physical world are a recent product of a great deal of conceptual, technological and experimental effort. Earlier societies lacked our interpretation of physical reality, so it is not surprising that our modern concept of consciousness is absent from ancient Greek, Chinese and the English language prior to the seventeenth century. Bubbles of experience were once understood in relation to an invisible world of gods and spirits. Once we started to believe in a physical world of atoms and forces, the colourful conscious world (that is manifestly not composed of atoms and forces) emerged as a separate area of inquiry.

One potential problem for this interpretation of consciousness is that it was not developed by the ancient atomists. Since they believed that colours, sounds and smells are not properties of atoms, it would have been natural to place them in a second substance, such as mind or consciousness. So why was consciousness (or a similar concept) absent from ancient Greek, but developed by atomists in the seventeenth century?

This problem would be resolved if the ancient atomists did invent a word for consciousness that did not enter common usage and was lost, or if they expressed the concept in a more indirect way. Although very little material is left from the ancient Greek atomists, it might be possible to find traces of a concept of consciousness in their work. A second possibility is that the ancient atomists might have believed that secondary qualities could be reduced to primary qualities. Plenty of people today believe that consciousness can be reduced to the physical world, so it would not be surprising if the ancient atomists had a similar view.29 It is also possible that the consequences of ancient atomism were not fully worked out. At the time atomism was one of a large number of highly speculative theories about the world and it is conceivable that the small number of people who believed in atomism did not have the time or resources to develop it fully. Today our theories about the physical world are subject to wide agreement, which has led to a general need for a concept of consciousness to contain the properties that have been excluded from the physical world.

2.6 Summary

Most of our lives are spent in a state of naive realism in which we attribute colours, sounds and smells to objects in our environment. I developed the concept of a bubble of experience to describe how we only perceive part of the world at one time, and to accommodate observations about dreams, imagination and hallucination.

The physical world is an invisible source of signals that interact with our sense organs to produce patterns in our brains that are somehow connected with our bubbles of experience. There is unlikely to be any resemblance between the contents of our bubbles of experience and the physical world.

When science eliminated sensory properties from the physical world it was necessary to find a way of grouping, describing and explaining the colours, sounds and smells that we continue to encounter in daily life. We solved this problem by inventing the modern concept of consciousness. ‘Consciousness’ is another name for our bubbles of experience, which contain the sensory properties that science removed from the physical world.