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There is no subject of which mankind is more profoundly ignorant than the problem of consciousness.  It must be a natural phenomena, but we may never fully understand how or why it emerges from natural processes.

Table of Contents

Three Great Unanswered Questions
Modern science has given us a remarkable understanding of the universe in which we live.  Except for situations involving extremely high energies and some questions related to cosmology, the standard model in physics is accurate and comprehensive.  Cosmology has provided an answer to the great question of how the universe was created.  The theory of evolution has provided an answer to the question of our own origins. Important unanswered questions certainly remain; e.g. regarding the inconsistency of quantum theory and general relativity in physics, the nature of dark matter and energy in cosmology, and many of the details of the biology of the human body.  However, there are very few profound, fundamental unanswered questions left.

I believe that there are three such questions1:

  1. How did life begin on earth?  – We know that once life began replicating, evolution by natural selection provided a mechanism for it to change and become more complex.  But we do not understand the origin of the first “replicator”, to use Richard Dawkin’s terminology2.
  2. Is there extraterrestrial life? – It seems highly probably that because life originated on earth, it has originated independently elsewhere in the universe.  However, no evidence to support this hypothesis has yet been found.
  3. What is consciousness? – How is it that consciousness can provide us with such a rich and intense experience?  How do we feel emotion, pleasure, and pain?

The first question is indeed profound, however numerous plausible theories for the origin of life of been proposed3.  Whether or not we ever solve this mystery is simply a question of whether supporting evidence for any of the theories will be found.  It would be a huge advance if life could be created from inanimate matter in the laboratory.  This is extremely challenging because of its complexity, but the fundamental knowledge to do so seems to exist.

I suspect that the answer to the second question is close at hand.  Regarding that question, in the past 20 years roughly 1000 extrasolar planets have been discovered4.  As our ability to explore these planets improves, evidence for extraterrestrial life should emerge.

On the other hand, in my opinion the third question, the nature of consciousness, is the most profound and difficult problem facing science today.  Indeed, the deepest mysteries of consciousness may never be solved.

Definitions & Types of Consciousness
Many philosophers believe that consciousness is essentially a primitive, that “there is a broadly shared underlying intuition about what consciousness is”5.  I agree, although there are several slightly different uses of the word “consciousness”, and we must be clear about which one applies in this case.  Dictionary.com defines consciousness as “awareness of one’s own existence, sensations, thoughts, surroundings, etc.”6.  The Stanford Encyclopedia of Philosophy provides definitions for several different uses of the word.  The most appropriate in this context are the senses of “sentience” and “wakefulness”, i.e., “An animal, person, or other cognitive system may be regarded as conscious… in the generic sense of simply being a sentient creature, one capable of sensing and responding to its world… One might further require that the organism actually be exercising such a capacity rather than merely having the ability or disposition to do so”7.

In my opinion, the most extraordinary, and therefore defining, feature of consciousness is the phenomenon of subjective experience.  In particular, an agent that is conscious has the ability to experience or be aware of sensations such as pain and pleasure.  The essence of consciousness is the rich, compelling, often intense nature of this subjective experience.  As I will discuss in more detail below, it is this essence of consciousness that makes it so mysterious and difficult to understand.

It should also be noted that consciousness is not an absolute, black or white affair.  It is an objective fact that there are many different degrees of consciousness.  A case in point is sleep, which is often perceived to be a single discrete state other than wakefulness.  While the transition from sleep to wakefulness can be abrupt, the transition in the other direction is a continuum in which “the brain progressively disengages from the external world”8.  Once we are fully asleep, our mind cycles between five separate stages, each with a different level on consciousness9.  We know from subjective experience that sleep has at least two stages, with the dream state clearly being a state between full consciousness and unconsciousness.  There is also ample medical evidence for degrees of consciousness.  Anesthesiologists typically use complex analysis of EEG data to determine a patient’s level of awareness10.

Another apparent example of different levels of consciousness may be found in animals.  It would appear that cats and dogs have a level of consciousness that is at least close to ours11.  On the other hand, it is highly doubtful that extremely primitive life forms like nematode roundworms have a state of consciousness, because they are not large enough to have the requisite nervous system.  Since there is a continuum of complexity between the extremely primitive and most advanced species of animals, it is very likely that there is a corresponding continuum in the degree of consciousness experienced by these species.

Theories of Consciousness
Since consciousness is a long-time subject of philosophical speculation, and has only recently become a serious subject of scientific inquiry12, a very large number of theories of consciousness have been proposed.  The Stanford Encyclopedia of Philosophy lists six different categories of theories13.  The following is essentially a synopsis of what is written there:

  • Representational theories: These theories basically say that consciousness consists of nothing more than the things that we perceive and know, its “representational features”.  I am sure that these theorists see a deeper meaning in this term than simple symbolic representation, but if this is not the case, it would seem that any information processing system, perhaps with sensors to give it information about the external world, could be considered “conscious” by this definition.  Note that while any theory of consciousness will have representational aspects, representational theories are those that are purely representational; they claim that what we perceive and know is exactly all that there is to consciousness.
  • High-order theories: These theories claim that consciousness amounts to the fact that an information processing system has a representation of itself, its perceptions, and its knowledge.  Proponents of this state sometimes speak of having awareness rather than just a representation, although to me “awareness” is just as ambiguous as “consciousness”.
  • Cognitive theories: These theories seek to explain consciousness in terms of cognitive processes.  Thus, they are like high-order theories, except that they involve more complexity than simply awareness of oneself.  A leading cognitive theory is Daniel Dennett’s Multiple Drafts Model, in which consciousness is nothing but memory and awareness of memory, although memories can be edited and corrected as new information about a particular memory becomes available.
  • Neural theories: These theories seek to explain consciousness simply in terms of activities of neurons in the brain.  In particular, they seek to correlate specific subjective phenomenon with precise physical processes in specific parts of the brain.
  • Quantum theories: These tend to be neural theories that include a role for quantum mechanics.  My interpretation of them is that since purely neural theories are deterministic, the role of quantum mechanics is to introduce a random element to mental processes.
  • Non-physical theories: This category encompasses all theories that are not purely natural, in that they hypothesize at least some supernatural role in consciousness.  In essence, these theories embrace Cartesian Dualism, which claims that the mind is a separate type of substance, process, or realm from the physical body.

It is clear that the first five types of theory, the natural, or physicalist categories, also represent different approaches to the problem of consciousness.  Most likely a final theory of consciousness will be found by combining results from all five of these approaches.  Each of them attempts to explain the process of consciousness, and could provide the basis for attempting to create artificial consciousness (or a simulation of consciousness).  On the other hand, none of them seems to offer any explanation of how subjective experience is possible.

Consciousness as a Natural Phenomenon
As stated above, most theories of consciousness are physicalist, in that they assume that consciousness is a wholly natural phenomenon.  I believe that this assumption is warranted.  The main reason is that there are compelling reasons in general to believe that there are no such things as supernatural phenomena14.  There is also ample evidence that the various stages and features of consciousness are correlated with physical features of the brain.  For example:

  • Each stage of sleep produces a distinct type of brain wave.  For example, stage 1 of “light” sleep produces “high amplitude theta waves, which are very slow brain waves”.  On the other hand, stage 4 of “deep sleep” produces “slow brain waves known as delta waves9.
  • Similarly, as mentioned above, anesthesiologists monitor brain waves via EEG to determine the level of consciousness in patients undergoing surgery.
  • Various disorders of the brain which affect conscious perception are caused by damage to specific areas of the nervous system and/or brain.  An example is blindsight, a syndrome in which people who report that they are blind still respond to visual stimuli as if they can see.  It is caused by damage to the primary visual cortex15.  Other fascinating examples include face blindness, or the inability to recognizes faces, caused by damage to the fusiform gyrus on both sides of the brain, and motion blindness, in which the world is perceived as “snapshots” that only change every few seconds, caused by damage to the middle temporal area of both sides of the brain16.
  • It is well known that psychoactive drugs such as LSD can cause hallucinations and other significant alterations to our perception of reality.  Unless these drugs have some kind of magical ability, their effects must be purely physical or natural.

While it is difficult to prove a negative, there is ample evidence that natural phenomena play at least a major role in perception and consciousness.

The Problem of Consciousness
The problem with consciousness is this: despite the many good reasons to believe that consciousness is a wholly natural phenomenon and can be reduced to a physical explanation, it is extremely difficult to imagine how this could be possible.  Even if we completely understood the physical mechanism of consciousness, would we have an understanding of how that mechanism resulted in our subjective, conscious experience?  As Leibniz wrote in Monadology:

Supposing that there were a machine whose structure produced thought, sensation, and perception, we could conceive of it as increased in size with the same proportions until one was able to enter into its interior, as he would into a mill.  Now, on going into it he would find only pieces working upon one another, but never would he find anything to explain perception17.

Leibniz’s comment regarding a conscious machine was rather prophetic of the modern science of “artificial intelligence”, or “AI”.  Whether or not the project of AI will ever succeed is an open debate.  Proponents of “weak AI” believe that some day we may be able to simulate consciousness, while those of “strong AI” believe that we will at some point succeed in creating a machine that is truly conscious.  John Searle’s famous “Chinese Room” argument, which is essentially a modern version of Leibniz’s, attempts to demonstrate that strong AI could never be possible18.

As a thoroughgoing naturalist, and because consciousness clearly exists, I believe that strong AI is possible.  However, I am not sure that we could ever distinguish weak AI from strong AI.  Suppose that eventually a robot could be created that appeared to be fully conscious.  In particular, this robot would appear to respond to external stimuli and to have intense subjective experiences such as pain or pleasure.  How could we know that the robot really felt these experiences, and was not just an unconscious machine cleverly programmed to appear to have them?  I do not see any way to distinguish these two cases.

The same problem could even exist in a human in the form of a philosophical zombie, “a hypothetical being that is indistinguishable from a normal human being except in that it lacks conscious experience”19.  If such a being ever existed, how could we possibly distinguish it from a normal human being?  It is for this reason that some modern philosophers do not even think that consciousness is a necessary phenomenon20.  Humans and society could be functioning just as well as it is today if we were all philosophical zombies.

While psychology, neuroscience, and artificial intelligence have begun to chip away at the problem of consciousness, we still have very little true understanding of what consciousness is.  The nature of consciousness constitutes one of the last remaining truly profound, unanswered questions in science.  All of the evidence points to the fact that consciousness is a wholly natural phenomenon.  Being a fully empirical subject, I believe that one day we will be understand the mechanism of consciousness; i.e., that the goal of soft AI will be achieved, in that we will be able to create a machine that at least appears to be conscious.  We may never be able to answer, however, the question of whether or not that machine truly is conscious.  Indeed, we may never really understand the mystery of the phenomenal experience of consciousness.

End Notes

  1. These questions are all scientific in nature, in that they can in principle be answered empirically.  There are certainly other profound questions that have yet to be answered, most notably regarding, the nature of universals, the veracity of the scientific method, and the foundation of ethics, which are all problems in philosophy.  There are also philosophical questions about scientific subjects, such as the interpretation of quantum theory, and the nature of time.
  2. Dawkins, Richard, The Selfish Gene, Oxford University Press, Oxford, GB (1976 edition), pg. 12.
  3. For a summary of some leading theories see “Abiogenesis”, Wikipedia, URL = <http://en.wikipedia.org/wiki/Abiogenesis>.
  4. “Extrasolar planet”, Wikipedia, URL = <http://en.wikipedia.org/wiki/Exoplanets>.
  5. “Consciouness”, Wikipedia, URL = <http://en.wikipedia.org/wiki/Consciousness>.
  6. “consciousness”, Dictionary.com, URL = <http://dictionary.reference.com/browse/consciousness?s=t>.
  7. Van Gulick, Robert, “Consciousness”, The Stanford Encyclopedia of Philosophy (Summer 2011 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/sum2011/entries/consciousness/>, section 2.1 Creature Consciousness.
  8. Wolchover, Natalie, “How Do We Fall Asleep”, LiveScience, April 3, 2012, URL=<http://www.livescience.com/19462-fall-asleep.html>.
  9. Cherry, Kendra, “Stages of Sleep”, About.com Psychology, URL=<http://psychology.about.com/od/statesofconsciousness/a/SleepStages.htm>.
  10. Lang, Joshua, “Awakening”, The Atlantic, January/February 2013, URL=<http://www.theatlantic.com/magazine/archive/2013/01/awakening/309188/2/>.
  11. This was not always believed to be the case.  For example, “Descartes regarded nonhuman animals as machines, devoid of mind and consciousness”.  See Hatfield, Gary, “René Descartes”, The Stanford Encyclopedia of Philosophy (Summer 2011 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/sum2011/entries/descartes/>, Section 4. The New Science.
  12. “Consciouness”, Wikipedia, op. cit., Scientific study.
  13. Van Gulick, op. cit., Section 9. Specific Theories of Consciousness
  14. My reasons for believing that supernatural phenomena do not exist are described in my essay on Naturalism & Theology.
  15. “Blindsight”, Wikipedia, URL = <http://en.wikipedia.org/wiki/Blindsight>.
  16. “Brain damage and perception”, Your Amazing Brain, URL = <http://www.youramazingbrain.org/brainchanges/braindamage.htm>.
  17. Leibniz, G.W., Monadology, (1686), Part 17.  Available online at <http://evans-experientialism.freewebspace.com/leibnitz.htm>.
  18. See for example Cole, David, “The Chinese Room Argument”, The Stanford Encyclopedia of Philosophy (Summer 2013 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/sum2013/entries/chinese-room/>
  19. “Philosophical zombie”, Wikipedia, URL = <http://en.wikipedia.org/wiki/Philosophical_zombie>.
  20. See for example, “Consciousness at Center Stage”, American Scientist, Vol. 89, No. 6 (November-December 2001), URL=<http://www.americanscientist.org/bookshelf/pub/consciousness-at-center-stage>.

November, 2013


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