Kinkazzo Burning
~ reflections & disquisitions
It takes both sunshine and rain to make a rainbow...

Where's the Key to Consciousness?

~The Neural Basis of Consciousness
~Reality And Consciousness: Turning The Superparadigm Inside Out

Leonardo's Brain


Christof Koch and Francis Crick
(November 4, 1999)

Abstract: The physical basis of consciousness appears to be the most singular challenge to the scientific, reductionist world view. In the closing years of the second millennium, advances in the ability to record the activity of individual neurons in the brains of monkeys or other animals while they carry out particular tasks, combined with the explosive development of functional brain imaging in normal humans, has lead to a renewed empirical program to discover the scientific explanation of consciousness. This article reviews some of the relevant experimental work and argues that the most advantageous strategy for now is to focus on discovering the neuronal correlates of consciousness.

Consciousness, neural basis of

Consciousness is a puzzling state-dependent property of certain types of complex, adaptive systems. The best example of one type of such systems is a healthy and attentive human brain. If the brain is anaesthetized, consciousness ceases. Small lesions in the midbrain and thalamus of patients can lead to a complete loss of consciousness, while destruction of circumscribed parts of the cerebral cortex of patients can eliminate very specific aspects of consciousness, such as the ability to be aware of motion or to recognize objects as faces, without a concomitant loss of vision in general. Given the similarity in brain structure and behavior, biologists commonly assume that at least some animals, in particular non-human primates, share certain aspects of consciousness with humans. Brain scientists, in conjunction with cognitive neuroscientists, are exploiting a number of empirical approaches that shed light on the neural basis of consciousness. Since it is not known to what extent artificial systems, such as computers and robots, can become conscious, this article will exclude these from consideration.

1. Some Common Neurobiological Assumptions

By and large, neuroscientists have made a number of working assumptions that, in the fullness of time, need to be justified more fully.

1. There is something to be explained; that is, the subjective content associated with a conscious sensation---what philosophers refer to as qualia---does exist and has its physical basis in the brain. To what extent qualia and all other subjective aspects of consciousness can or cannot be explained within a reductionist framework remains highly controversial (Chalmers 1995).

2. Consciousness is a vague term with many usages and will, in the fullness of time, be replaced by a vocabulary that more accurately reflect the contribution of different brain processes (for a similar evolution, consider the usage of memory, that has been replaced by an entire hierarchy of more specific concepts). Common to all forms of consciousness is that it feels like something (e.g., to "see blue," to "experience a head-ache", or to "reflect upon a memory"). Self-consciousness is but one form of consciousness.

It is possible that all the different aspects of consciousness (smelling, pain, visual awareness, affect, self-consciousness, and so on) employ a basic common mechanism or perhaps a few such mechanisms. If one could understand the mechanism for one aspect, then one will have gone most of the way towards understanding them all.

3. Consciousness is a property of the human brain, a highly evolved system. It therefore must have a useful function to perform. Crick and Koch (1998) assume that the function of the neuronal correlate of consciousness is to produce the best current interpretation of the environment---in the light of past experiences---and to make it available, for a sufficient time, to the parts of the brain which contemplate, plan and execute voluntary motor outputs (including language). This needs to be contrasted with the on-line systems that bypass consciousness but that can generate stereotyped behaviors (see below).

Note that in normally developed individuals motor output is not necessary for consciousness to occur. This is demonstrated by lock-in syndrome in which patients have lost (nearly) all ability to move yet are clearly conscious.

4. At least some animal species posses some aspects of consciousness. In particular, this is assumed to be true for non-human primates, such as the macaque monkey. Consciousness associated with sensory events in humans is likely to be related to sensory consciousness in monkeys for several reasons. Firstly, trained monkeys show similar behavior to that of humans for many low-level perceptual tasks (e.g. detection and discrimination of visual motion or depth; Wandell 1995). Secondly, the gross neuroanatomy of humans and non-human primates are rather similar once the difference in size has been accounted for. Finally, functional magnetic resonance imaging of human cerebral cortex is confirming the existence of a functional organization in sensory cortical areas similar to that discovered by the use of single cell electrophysiology in the monkey (Tootell, Hadjikhani, Mendola, Marrett and Dale 1998). As a corollary, it follows that language is not necessary for consciousness to occur (although it greatly enriches human consciousness).

2. Enabling, Modulating and Specific Factors

It is important to distinguish the general, enabling factors in the brain that are needed for any form of consciousness to occur from modulating ones that can up- or down-regulate the level of arousal, attention and awareness and from the specific factors responsible for a particular content of consciousness.

An easy example of an enabling factor would be a proper blood supply. Inactivate the heart and consciousness ceases within a fraction of a minute. This does not imply that the neural correlate of consciousness is in the heart (as Aristotle thought). A neuronal enabling factor for consciousness is the intralaminar nuclei of the thalamus. Acute bilateral loss of function in these small structures that are widely and reciprocally connected to the basal ganglia and cerebral cortex leads to immediate coma or profound disruption in arousal and consciousness (Bogen 1995).

Among the neuronal modulating factors are the various activities in nuclei in the brain stem and the midbrain, often collectively referred to as the reticular activating system, that control in a widespread and quite specific manner the level of noradrenaline, serotonin and acetylcholine in the thalamus and forebrain. Appropriate levels of these neurotransmitters are needed for sleep, arousal, attention, memory and other functions critical to behavior and consciousness (Baars 1997).

Yet any particular content of consciousness is unlikely to arise from these structures, since they probably lack the specificity necessary to mediate a sharp pain in the right molar, the percept of the deep, blue California sky, the bouquet associated with a rich Bordeaux, a haunting musical melody and so on. These must be caused by specific neural activity in cortex, thalamus, basal ganglia and associated neuronal structures. The question motivating much of the current research into the neuronal basis of consciousness is the notion of the minimal neural activity that is sufficient to cause a specific conscious percept or memory (see below).

For instance, when a subject consciously perceives a face, the retinal ganglion cells whose axons make up the optic nerve that carries the visual information to the brain proper are firing in response to the visual stimulus. Yet it is unlikely that this retinal activity directly correlates with visual perception. While such activity is evidently necessary for seeing a physical stimulus in the world, retinal neurons by themselves do not give rise to consciousness.

Given the comparative ease with which the brains of animals can be probed and manipulated, it seems opportune at this point in time to concentrate on the neural basis of sensory consciousness. Because primates are highly visual animals and much is known about the neuroanatomy, psychology and computational principles underling visual perception, vision has proven to be the most popular model systems in the brain sciences.

3. Information Processing in the Brain that Bypasses Consciousness

Cognitive and clinical research demonstrates that much complex information processing can occur without involving consciousness. This includes visual, auditory and linguistic priming, implicit memory, the implicit recognition of complex sequences, automatic behaviors such as driving a car or riding a bicycle and so on (Velmans 1991) and the dissociations found in patients with lesions in cerebral cortex (e.g., such as residual visual functions in the professed absence of any visual awareness known as clinical blindsight in patients with lesions in primary visual cortex; Weiskrantz 1997).

The cognitive scientist Jackendoff (1987) argues at length against the notion that consciousness and thoughts are inseparable and that introspection can reveal the contents of the mind. What is conscious about thoughts are sensory aspects, such as visual images, sounds or silent speech. Both the process of thought and its content are not directly accessible to consciousness. Indeed, one tradition in psychology and psychoanalysis---going back to Sigmund Freud---hypothesizes that higher-level decision making and creativity are not accessible at a conscious level, although they influence behavior.

Within the visual modality, Milner and Goodale (1995) have made a masterful case for the existence of so-called on-line systems that by-pass consciousness. Their function is to mediate relative stereotype visuo-motor behaviors, such as eye and arm movements, reaching, grasping, posture adjustments and so on, in a very rapid, reflex-like manner. On-line systems work in egocentric coordinate systems, and lack certain types of perceptual illusions (e.g. size illusion) as well as direct access to working memory. This contrasts well with the function of consciousness alluded to above, namely to synthesize information from many different sources and use it to plan behavioral patterns over time. Milner and Goodale argue that on-line systems are associated with the dorsal stream of visual information in the cerebral cortex, originating in the primary visual cortex (V1) and terminating in the posterior parietal cortex.

4. The Neuronal Correlate of Consciousness (NCC)

The problem of consciousness can be broken down into several separate questions. Most, if not all of these, can then be subjected to scientific inquiry.

The major question that neuroscience must ultimately answer can be bluntly stated as follows: It is probable that at any moment some active neuronal processes in our head correlates with consciousness, while others do not; what is the difference between them? The specific processes that correlate with the current content of consciousness are referred to as the neuronal correlate of consciousness, or as the NCC. Whenever some information is represented in the NCC it is represented in consciousness. The NCC is the minimal (minimal, since it is known that the entire brain is sufficient to give rise to consciousness) set of neurons, most likely distributed throughout certain cortical and subcortical areas, whose firing directly correlates with the perception of the subject at the time. Conversely, stimulating these neurons in the right manner with some yet unheard of technology should give rise to the same perception as before.

Discovering the NCC and its properties will mark a major milestone in any scientific theory of consciousness.

What is the character of the NCC? Most popular has been the belief that consciousness arises as an emergent property of a very large collection of interacting neurons (for instance, Libet 1993). In this view, it would be foolish to locate consciousness at the level of individual neurons. An alternative hypothesis is that there are special sets of "consciousness" neurons distributed throughout cortex and associated systems. Such neurons represent the ultimate neuronal correlate of consciousness, in the sense that the relevant activity of an appropriate subset of them is both necessary and sufficient to give rise to an appropriate conscious experience or percept (Crick and Koch 1998). Generating the appropriate activity in these neurons, for instance by suitable electrical stimulation during open skull surgery, would give rise to the specific percept.

Any one subtype of NCC neurons would, most likely, be characterized by a unique combination of molecular, biophysical, pharmacological and anatomical traits. It is possible, of course, that all cortical neurons may be capable of participating in the representation of one percept or another, though not necessarily doing so for all percepts. The secret of consciousness would then be the type of activity of a temporary subset of them, consisting of all those cortical neurons which represent that particular percept at that moment. How activity of neurons across a multitude of brain areas that encode all of the different aspects associated with an object (e.g. the color of the face, its facial expression, its gender and identity, the sound issuing from its mouth) is combined into a single percept remains puzzling and is known as the binding problem.

What, if anything, can we infer about the location of neurons whose activity correlates with consciousness? In the case of visual consciousness, it was surmised that these neurons must have access to visual information and project to the planning stages of the brain; that is to premotor and frontal areas (Fuster 1997). Since no neurons in the primary visual cortex of the macaque monkey project to any area forward of the central sulcus, Crick and Koch (1998) propose that neurons in V1 do not give rise to consciousness (although V1 is necessary for most forms of vision, just as the retina is). Ongoing electrophysiological, psychophysical and imaging research in monkeys and humans is evaluating this prediction.

While the set of neurons that can express any one particular conscious percept might constitute a relative small fraction of all neurons in any one area, many more neurons might be necessary to support the firing activity leading up to the NCC. This might resolve the apparent paradox between clinical lesioning data suggesting that small and discrete lesions in cortex can lead to very specific deficits (such as the inability to see colors or to recognize faces in the absence of other visual losses) and the functional imaging data that any one visual stimulus can activate large swaths of cortex.

Conceptually, several other questions need to be answered about the NCC. What type of activity corresponds to the NCC (it has been proposed as long ago as the early part of the twentieth century that spiking activity synchronized across a population of neurons is a necessary condition for consciousness to occur)? What causes the NCC to occur? And, finally, what effect does the NCC have on postsynaptic structures, including motor output.

5. Experimental Approaches

A promising experimental approach to locate the NCC is the use of bistable percepts in which a constant retinal stimulus gives rise to two percepts alternating in time, as in a Necker cube (Logothetis 1998). One version of this is binocular rivalry in which a small image, say of a horizontal grating, is presented to the left eye and another image, say a vertical grating, is shown to the corresponding location in the right eye. In spite of the constant visual stimulus, observers "see" the horizontal grating alternate every few seconds with the vertical one (Blake 1989). The brain does not allow for the simultaneous perception of both images.

It is possible, though difficult, to train a macaque monkey to report whether it is currently seeing the left or the right image. The distribution of the switching times and the way in which changing the contrast in one eye affects these leaves little doubt that monkeys and humans experience the same basic phenomenon. In a series of elegant experiments, Logothetis and colleagues (Logothetis 1998) recorded from a variety of visual cortical areas in the awake macaque monkey while the animal performed a binocular rivalry task. In primary visual cortex, only a small fraction of cells modulate their response as a function of the percept of the monkey, while 20 to 30% of neurons in higher visual areas in cortex do so. The majority of cells increased their firing rate in response to one or the other retinal stimulus with little regard to what the animal perceives at the time. In contrast, in a high-level cortical area such as the inferior temporal (IT) cortex, almost all neurons responded only to the perceptual dominant stimulus (in other words, a ``face" cell only fired when the animal indicated by its performance that it saw the face and not the pattern presented to the other eye). This makes it likely that the NCC involves activity in neurons in the inferior temporal lobe. Lesions in the homologue area in the human brain is known to cause very specific deficits in the conscious face or object recognition. However, it is possible that specific interactions between IT cells and neurons in parts of the prefrontal cortex are necessary in order for the NCC to be generated.

Functional brain imaging in humans undergoing binocular rivalry has revealed that areas in the right prefrontal cortex are activate during the perceptual switch from one percept to the other (Lumer, Friston and Rees 1998).

A number of alternate experimental paradigms are being investigated using electrophysiological recordings of individual neurons in behaving animals and human patients, combined with functional brain imaging. Common to these is the manipulation of the complex and changing relationship between physical stimulus and the conscious percept. For instance, when subjects are forced to rapidly respond to a low saliency target, both monkeys and humans sometimes claim to consciously perceive such a target in the absence of any physical target (false alarm) or fail to respond to a target (miss). The NCC in the appropriate sensory area should mirror the perceptual report under these dissociated conditions. Visual illusions constitute another rich source of experiments that can provide information concerning the neurons underlying these illusory percepts. A classical example is the motion aftereffect in which a subject stares at a constantly moving stimulus (such as a waterfall) for a fraction of a minute or longer. Immediately after this conditioning period, a stationary stimulus will appear to move in the opposite direction. Because of the conscious experience of motion, one would expect the subject’s cortical motion areas to be activate in the absence of any moving stimulus.

Future techniques, most likely based on the molecular identification and manipulation of discrete and identifiable subpopulations of cortical cells in appropriate animals, will greatly help in this endeavor.

Identifying the type of activity and the type of neurons that gives rise to specific conscious percept in animals and humans would only be the first, albeit critical, step in understanding consciousness. One also needs to know where these cells project to, their postsynaptic action, how they develop in early childhood, what happens to them in mental diseases known to affect consciousness in patients, such as schizophrenia or autism, and so on. And, of course, a final theory of consciousness would have to explain the central mystery, why a physical system with a particular architecture gives rise to feelings and qualia (Chalmers 1995).


Baars B J 1997 In the Theater of Consciousness: The Workspace of the Mind. Oxford University Press, Oxford

Blake R 1989 A neural theory of binocular rivalry. Psychol. Review 96: 145-167

Bogen J E 1995 On the neurophysiology of consciousness: I. An Overview. Consciousness & Cognition 4: 52-62

Chalmers D 1995 The Conscious Mind: In Search of a Fundamental Theory. Oxford University Press, Oxford

Crick F C, Koch C 1998 Consciousness and neuroscience. Cerebral Cortex 8: 97-107

Fuster J M 1997 The Prefrontal Cortex: Anatomy, Physiology, and Neuropsychology of the Frontal Lobe. 3rd ed. Lippincott-Raven, Philadelphia

Jackendoff R 1987 Consciousness and the Computational Mind. MIT Press, Cambridge, Massachusetts

Libet B 1993 Neurophysiology of Consciousness: Selected Papers and New Essays. Birkhauser, Boston

Logothetis N 1998 Single units and conscious vision. Philosophical Transactions of the Royal Society of London B, 353: 1801-1818

Lumer E, Friston K J, Rees G 1998 Neural basis of perceptual rivalry in the human brain. Science 280: 1930-1933

Milner D, Goodale M 1995 The Visual Brain in Action. Oxford University Press, Oxford

Tootell R B H, Hadjikhani N K, Mendola J D, Marrett S, Dale AM 1998 From retinotopy to recognition: fMRI in human visual cortex. Trends Cognitive Sciences 2: 174-183

Velmans M 1991 Is human information processing conscious? Behavioral Brain Science 14: 651-726

Wandell B A 1995 Foundations of Vision. Sinauer Associates, Sunderland, Massachusetts

Weiskrantz L 1997 Consciousness lost and found. Oxford University Press, Oxford
Brainy mind

--Prof. Dr Christof Koch is at the Division of Biology, 139-74, California Institute of Technology, Pasadena, CA 91125.

--Dr Francis Crick (1916-2004), Nobel Prize for Physiology/Medicine, was last at the Salk Institute, in La Jolla, CA 92037.

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For further developments on the subject, read the interesting paper by Christof Koch and Naotsugu Tsuchiya: “Attention and consciousness: two distinct brain processes” (2007).

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Now another challenging perspective (with an Eastern slant - well, we gotta give space to guru en-Light-enment too)...

Light waves

By Peter Russell

Thomas Kuhn coined the term "paradigm" to refer to the beliefs and assumptions that underlie a particular science. But beneath all our scientific paradigms lies an even deeper and more pervasive assumption. It is the belief in the primacy of the material world. When we fully understand the world of space, time and matter, we will, it is held, be able to account for everything in the cosmos. Being the paradigm behind all our scientific paradigms, this worldview has the status of a "superparadigm". Eminently successful as this model has been at explaining the world around us, it has very little to say about the non-material world of mind.

Nothing in the physical sciences predicts the phenomenon of consciousness. Yet its reality is apparent to each and every one of us. As far as the current superparadigm is concerned consciousness is a great anomaly.

When paradigm anomalies first arise they are usually overlooked or rejected. Or, if they cannot be so easily discarded, they are incorporated in some way, often clumsily, into the existing model. Witness the attempts of mediaeval astronomers, wedded to Plato's belief in the perfection of circular motion, trying to explain irregularities in planetary motion with theories of epicycles (circles rolling along circles).

Western science has followed a similar pattern in its approach to consciousness. For the most part it ignored consciousness completely. More recently, as developments across a range of disciplines have shown that consciousness cannot be so easily sidelined, science has made various attempts to account for it. Some have looked to quantum physics, some to information theory, others to neuropsychology. But the failure of these approaches to make any appreciable headway into the problem of consciousness suggests that they may be on the wrong track.

All these approaches assume that consciousness somehow arises from, or is dependent upon, the world of space-time-matter. In one way or another they are trying to accommodate the anomaly of consciousness within the materialist superparadigm. The underlying beliefs are seldom, if ever, questioned.

When Newton proposed his laws of motion, he turned the problem of what made things move into the foundation stone of his new paradigm; objects continued to move unless acted upon by some external force. When Einstein formulated his Special Theory of Relativity, he took the problem of the constancy of the speed of light and made it an axiom of the new model. I believe we need to do the same with the problem of consciousness. Instead of trying to explain consciousness within the current superparadigm, we need to accept that consciousness is as fundamental as matter—in some ways, more fundamental. When we do we find that the key ingredients for a new superparadigm are already in place; all we need to do is put them together.


The key to this new model of reality is an understanding of how we perceive reality. Advances in physics, psychology, and philosophy have shown that reality is not what it seems. Take vision, for example. When I look at a tree, light reflected from its leaves is focused onto cells in the retina of my eye, where it triggers a cascading chemical reaction releasing a flow of electrons. Neurons connected to the cells convey these electrical impulses to the brain’s visual cortex, where the raw data is processed and integrated. Then—in ways that are still a complete mystery—an image of the tree appears in my consciousness. It may seem that I am directly perceiving the tree in the physical world, but what I am actually experiencing is an image generated in my mind.

The same is true of every other experience. All that I see, hear, taste, touch, smell and feel has been created from the data received by my sensory organs. All I ever know of the world around are the mental images constructed from that data. However real and external they may seem, they are all phenomena within my mind.

This simple fact is very hard to grasp; it goes against all our experience. If there is anything about which we feel sure, it is that the world we experience is real. We can see, touch and hear it. We can lift heavy and solid objects; hurt ourselves, if we're not careful, against their unyielding immobility. It seems undeniable that out there, around us, independent and apart from us, stands a physical world, utterly real, solid and tangible.

But the world of our experience is no more "out there" than are our dreams. When we dream we create a reality in which events happen around us, and in which we perceive other people as individuals separate from us. In the dream it all seems very real. But when we awaken we realize that everything in the dream was actually a creation of our own mind.

The same process of reality generation occurs in waking consciousness. The difference is that now the reality that is created is based on sensory data and bears a closer relationship to what is taking place in the real world. Nevertheless, however real it may seem, it is not actually "the real world". It is still an image of that world created in the mind.


It is important to distinguish between two ways in which we use the word "reality". There is the reality we experience, our image of reality; and there is the underlying reality that has given rise to this experience. The underlying reality is the same for all observers. It is an absolute reality. The reality I experience, the reality generated in my mind, is a relative reality. It is relative to my point of view, my past experience, my human senses and my human brain.

The fact that we create our image of reality does not mean, as some people misconstrue, that we are creating the underlying reality. Whatever that reality is, it exists apart from our perception of it. When I see a tree there is something that has given rise to my perception. But I can never directly perceive this something. All I can ever know of it is the image appearing in my mind.

When, two centuries ago, Bishop Berkeley proposed that we know only what we perceive, his contemporaries debated whether or not a tree falling in a forest made a sound if no one was there to hear it. From what we now know of the psychophysiology of perception, we can say the answer is "No". Sound is not a quality of the underlying reality. There may be movements in the air, but the interpretation of those movements as sound is something that happens in the mind—whether it be the mind of a human being, a dog or a woodpecker.

Similarly with light. Whatever the tree is in physical reality, it is not green. Light of various frequencies is reflected from the tree to the retina of the eye, where cells respond to the amount of light in three frequency ranges (the three primary colors). But all that is passed back to the brain are electro-chemical impulses; there is no color here. The green I see is a quality created in consciousness. It exists only in the mind.

The same is true of our perception of distance. The pattern of light that falls on the retina creates a two-dimensional image of the world. The brain estimates distance by detecting slight differences between data from the left and right eyes, the focus of the eyes, relative movement, and past experience as to the likely size of a tree. From this data it calculates that the tree is fifty feet away. A three-dimensional image of the world is then created with the tree placed "out there" in that world, fifty feet away. Yet, however real it may seem, the quality of space and distance that we experience is created in the mind.


Long before modern science knew anything about the processes of perception or the structure of matter, the eighteenth-century German philosopher Immanuel Kant had drawn a clear distinction between our perception of reality and the actual object of perception. He argued that all we ever know is how reality appears to us—what he referred to as the phenomenon of our experience, "that which appears to be". The underlying reality he called the noumenon, meaning "that which is apprehended", the thing perceived.

At the time, Kant's arguments were a watershed in Western thinking. They were, as Kant himself saw, the equivalent of a Copernican Revolution in philosophy. Whereas Copernicus had effectively turned the physical universe inside out, showing that the movements of the stars are determined by the movement of the earth, Kant had turned the epistemological world inside out, putting the self firmly back at the center of things. We are not passive experiencers of the world; we are the creators of the world we experience.

Because all we ever know is the product of the mind operating on the raw sensory data, Kant reasoned that our experience is as much a reflection of the nature of the mind as it is of the physical world. This led him to one of his boldest and, at the time, most astonishing, conclusions of all. Time and space, he argued, are not inherent qualities of the physical world; they are a reflection of the way the mind operates. They are part of the perceptual framework within which our experience of the world is constructed.

It seems absolutely obvious to us that time and space are real and fundamental qualities of the physical world, entirely independent of my or your consciousness—as obvious as it seemed to people five hundred years ago that the sun moves round the earth. This, said Kant, is only because we cannot see the world any other way. The human mind is so constituted that it is forced to impose the framework of space and time on the raw sensory data in order to make any sense of it all.

Strange as Kant’s proposal may have seemed then, and strange as it may still seem to many of us today, contemporary science is proving him right.

Solar Light

The first significant scientific challenge to the assumption that space and time are absolutes came in 1905 with Einstein's Special Theory of Relativity. He showed that what we observe as space and what we observe as time are but two aspects of a more fundamental reality, which he called "the spacetime continuum". How much of this continuum manifests as space, and how much manifests as time varies from one observer to another, depending on their motion. Space and time may appear to us to be fixed qualities, but that is because we are not traveling at speeds close to that of light. If we did, things would look very different.

Just what the spacetime continuum itself is like we never know. Einstein agreed with Kant; all we ever know of the underlying reality are the ways in which it appears as the two very different qualities of space and time.

Although observers moving at different speeds may disagree on the amounts of time and space separating two events, they do agree, no matter how fast they may be moving, on the amount of spacetime separating them—what Einstein called the "interval". It is a little like cutting a string in two; cutting it in different places will give pieces of differing lengths, but the total length of string will always be the same. Similarly, any observation divides the spacetime interval into a certain amount of time and a corresponding amount of space, the exact proportions depending on the motion of the observer. (With the difference that the mathematical formula for the combination of space and time is not simple addition; it is more like "space squared minus time squared.")


In proposing his theory Einstein postulated that the speed of light was a universal constant. However fast you may be traveling, you will always measure the speed of light relative to you to be the same—186,000 miles per second. You can never catch up with light. Even if you were traveling at 185,990 miles per second, light would still pass you by at 186,000 miles per second.

Why should this be so? It seems totally counter-intuitive that the speed of light never varies. But this perplexing behavior takes on a rather different character when we distinguish our image of reality from the underlying reality. Space and time, and hence speed, are aspects of the phenomenal world; they have no meaning, it turns out, for light itself.

According to the equations of Special Relativity, as an observer's speed increases, time slows down, and length (in the direction of motion) contracts. At the speed of light, time has slowed to a standstill and length contracted to zero. Although no object with mass can ever attain the speed of light (the equations predict that it would then have an infinite mass), light itself does (by definition) travel at the speed of light. From light's point of view—and this after all must be the most appropriate perspective from which to consider the nature of light, not our matter-bound mode of experience—it travels no distance and takes no time to do so.

This reflects a unique property of light. In the spacetime continuum, the interval between the two ends of a light ray is always zero. How can we interpret this? We probably should not even try to interpret it. Any attempt to do so would make the mistake of applying concepts derived from our image of reality to the underlying reality. All we need to recognize is that, from light's perspective, this zero interval manifests as zero space and a corresponding amount of zero time.

However, when we in the world of sub-light speeds perceive light, we see a different manifestation of the zero interval. We observe a finite amount of space along with an "equal" amount of time. In our world, the light does travel through space and time. Since the total interval must be zero, the distance covered must exactly balance the time taken—that is, we must always observe 186,000 miles of space for every second of time. This we interpret as the speed of light. But this "speed" is not an intrinsic property of light itself; traveling no distance in no time, light has no need of speed. What we interpret as the speed of light is actually the ratio in which space and time manifest in our perception of reality. It is this ratio that is constant. And this is why all our measurements of the apparent speed of light are constant.


The fact that light itself knows no space or time resolves another difficult conundrum. In our image of reality we observe light traveling across space and time and so observe energy traveling from the point of emission of the light ray to its point of absorption. Naturally, we ask how the energy travels. Is it a wave, or is it a particle?

The answer, it seems, is both. In some situations light behaves as a continuous wave spreading out in space—but, curiously, a wave without a medium. In other situations it behaves as a particle traveling through space—but, equally curiously, a particle without mass. Physicists have accommodated these two strange and seemingly paradoxical conclusions by deciding that light is a "wave-particle." In certain circumstances it appears as a wave; in others as a particle.

But if we look at things from light’s point of view, the reality is very different. Since it did not travel through space and time, it needed no vehicle or mechanism of travel. Light itself has no need to be either a wave or a particle. From its own frame of reference—which is probably the most appropriate frame of reference from which to consider light—there is no duality, and no paradox.

The physicist’s conundrum appears only when we mistake our image of reality with the "thing in itself", and try to visualize light in concepts and terms appropriate to our image of reality—that is, waves and particles.


A photon is a single quantum of action. We are all familiar with quantities such as mass, velocity, acceleration, momentum and energy. Action is just another member of this family, but not one that we come across much in ordinary life. It is defined as the product of momentum and distance traveled, or, equivalently, energy and time. Thus the amount of action of speeding bullet is higher than the same bullet traveling more slowly across the same distance. Double the bullet's mass, and you get twice the action—which accords with our intuitive concepts of action.

To speak of light as pure action is both appropriate and strange, depending upon one’s point of view. In the world we experience, the world in which space and time exist, and light travels great distances at unmatchable speed, light seems to be nothing but action. It never rests; it never slows. From this frame of reference, action seems a most appropriate quality.

From its own frame of reference, however, light never goes anywhere. A photon covers no distance, and knows no time. Nor does it have any mass. Strange then, that something without mass, space or time should be the fundamental unit of action. Strange it may be; nevertheless, that is the nature of the underlying reality. Once again, nothing like what we expected. Nothing like the phenomenon generated in the mind.

Kant argued that space and time are characteristics not of the noumenon, the underlying reality, but of the mind. Quantum theory reveals that the same is true of matter. Matter is not to be found in the underlying reality; atoms turn out to be 99.99999999% empty space, and sub-atomic "particles" dissolve into fuzzy waves. Matter and substance seem, like space and time, to be characteristics of the phenomenon of experience. They are the way in which the mind makes sense of the no-thing-ness of the noumenon.


When we speak of "the material world", we think we are referring to the underlying reality, the object of our perception. In fact we are only describing our image of reality. The materiality we observe, the solidness we feel, the whole of the "real world" that we know, are, like color, sound, smell, and all the other qualities we experience, qualities manifesting in the mind. This is the startling conclusion we are forced to acknowledge; the "stuff" of our world—the world we know and appear to live within—is not matter, but mind.

The current superparadigm assumes that space, time and matter constitute the basic framework of reality, and consciousness somehow arises from this reality. The truth, it now appears, is the very opposite. As far as the reality we experience is concerned — and this remember is the only reality we ever know — consciousness is primary. Time, space and matter are secondary; they are aspects of the image of reality manifesting in the mind. They exist within consciousness; not the other way around.

Similar claims have often been made in spiritual teachings, particularly Indian philosophy [here we go…hold fast…]. Patanjali’s Yoga Sutra’s, for example, speak of the entire world as chitta vritti, "the modifications of mind-stuff". When physicists hear statements such as this, and take them to be referring to the physical world, they or are understandably perplexed and perhaps dismissive. But when we understand this to be a statement about the manifestation of our experienced world, it begins to make more sense.

If we consider the reality we experience, then we have to accept that in the final analysis they are correct: Consciousness is the essence of everything—everything in the known universe. It is the medium from which every aspect of our experience manifests. Every form and quality we ever experience in the world is an appearance within consciousness.


As mentioned at the outset, the very existence of consciousness is an insurmountable anomaly for the current superparadigm. How can something as seemingly unconscious as matter ever lead to something as immaterial as consciousness. The two could not be more radically different. The philosopher David Chalmers has dubbed this the "hard question" facing any science of consciousness. Even if we were to fully understand the workings of the brain, down to the tiniest detail, it would still leave unanswered the question as to why any of it should result in a conscious experience? Why doesn't it all go on in the dark, without any subjective aspect?

The question that is apparently being asked is: How does the underlying reality ever gives rise to consciousness? But never being able to know the underlying reality directly, we are not really in any position to even ask this question, let alone answer it. Indeed, for all we know, consciousness may be an intrinsic quality of the underlying reality In which case there is no hard question to answer.

The question that is actually being asked is: How does the material world—the world of space, time and matter—give rise to consciousness? But this is trying to account for consciousness in terms that are themselves manifestations of consciousness. Space, time, matter, and all the forms and structures we observe in the world, are aspects of the phenomenon arising in the mind; they are aspects of the image of reality appearing in consciousness.

The question we should be asking is the exact opposite. How is that consciousness, which seems so non-material, can take on the material forms that we experience? How do space, time, color, sound, texture, substance, and the many other qualities that we associate with the material world, emerge in consciousness? What is the process of manifestation within the mind?

But this is not a question that science may ever be able to answer. It is more in the domain of the mystic, and others in the more contemplative traditions, who have chosen to explore the nature of consciousness first hand.


Earlier I said that it was probably impossible not to see the world of our experience as "out there" around us. But it may be that some of those who have devoted themselves to meditation and observation of the arising of experience in the mind have developed sufficient inner clarity to see past appearances. Judging from various spiritual texts, they may have recognized, as a personal experience rather than an intellectual insight, that the entire phenomenal world is creation in the mind, and that consciousness is the primary stuff of their universe.

Such people—enlightened ones, we usually call them—are those who have experienced the new superparadigm. For them "I am That, Thou art That, and all this is That", as it is put in the Upanishads [not the Upanishads, nooooooo…!], or more simply "All is Brahman" (the Sanskrit word which might be translated as the One, or Essence).

In Western traditions, the same sentiments occur in the statement "I am God". But the word "God" has so many different meanings and associations that such statements are prone to considerable misunderstanding and confusion. To the lay person, the words "I am God" smack of extreme arrogance—particularly if there is the implication that "I", this particular individual human being, is God. To the more religious person, it sounds heretical, if not blasphemous, and some have burned at the stake for it. While to many scientists, such statements are meaningless, the symptoms of some delusion or pathology.

Science has looked out into deep space, back in "deep time" to the beginning of creation, and down into the "deep structure" of the cosmos, the very essence of matter, and is proud to tell us that it finds no need nor place for God—the Universe seems to work perfectly well without his assistance. But whoever said God is to be found "out there", in the realm of space, time and matter? This is a very naive and old-fashioned interpretation of God. When spiritual teachings refer to God they are, more often than not, pointing towards the realm of inner experience, not some thing in the physical realm. If we want to find God, we have to look within, into the realm of "deep mind"—a realm that science has yet to explore.

If we look more closely at the statements of those who have explored deep mind, they seem to be saying that the "I", that innermost essence of ourselves is a universal essence. Whatever we may be conscious of, the faculty of consciousness is something we all share. This consciousness is the one truth we cannot deny. It is the absolute certainty of our existence. It is eternal in that it is always there whatever the contents of our experience. It is the essence of everything we know. And, since every aspect of our experience is a manifestation in the mind, it is the creator of the world we know.

These qualities—truth, absolute, eternal, essence, creator—are amongst those traditionally associated with God. From this perspective, the statement "I am God" is not so puzzling or deluded after all. Although it might be more accurate to say that "I am" is God, or possibly, "God is consciousness".

Cosmic Light

The foundation stone of the Copernican Revolution was the realization that the Earth was not still, as had hitherto been supposed, and as daily experience seemed to confirm, but was spinning about its own axis. From this shift in perception was born a radically new model of the cosmos. The foundation stone of this discussion has been the distinction between the reality generated in the mind, and the underlying reality. Most of the time we are not aware of this distinction. We tacitly assume that things are as they appear, and that we are experiencing the world as it is. We think that the tree we see is the tree in itself.

When we realize that they are not the same thing at all, but are very different indeed, a revolutionary new model of reality emerges. Space, time and matter fall from their absolute status, to be replaced by light in the physical realm, and by consciousness (the inner light) in the world of experience. Instead of matter being primary, and the source of everything we know, including mind; consciousness becomes primary, and the source of everything, including matter, as we know it. For a second time, the universe has been turned inside out.

This shift in superparadigm has not happened yet. The existing model runs even deeper than did the geocentric view of the cosmos, and will probably meet even more obstacles than did the Copernican Revolution, (although now, somewhat ironically, it is science not the church that is the establishment, and will be the source of the greatest resistance). Nevertheless, I believe all the pieces are in place, they have only to be put together into a coherent model.

New paradigms stand or fall according to their ability to account for persistent anomalies, and incorporate new findings. The emerging new superparadigm accounts for consciousness—an intractable anomaly for the old model, remember. It offers radically new perspectives on some of the most perplexing problems in contemporary physics. And, most significantly, points towards a resolution of one of the oldest challenges of all—the reconciliation of the scientific worldview with the spiritual.


For more from Peter Russell, in case you like his light approach, click here: “Mysterious Light: A Scientist's Odyssey”


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