What is Consciousness?
The word “consciousness” is used in a number of different ways and that can lead to confusion. Ned Block is one worker who distinguishes different ways in which the word “consciousness” can be used [1]. The most notable distinction he makes is between what he calls “access consciousness” and “phenomenal consciousness”.
Access consciousness
If we are “access conscious” of something then that something is “poised for control of speech, reasoning and action” [1] or as “directly available for global control” [2]. An example of this, given in [11] chapter 11, is that of the belief: “The Thylacine tiger is extinct”. This belief is (1) available for the rational control of speech so that if the person was asked to name an extinct marsupial then they could say “thylacine”. (2) It is available for rational control of action so that if the person was asked to show a thylacine they would go to a museum rather than a zoo. (3) It is also available to be used in all sorts of reasoning. It thus satisfies Block's definition. A similar concept has been called “awareness” by David Chalmers [4 , page 28].
A third term to describe this use of the word consciousness is “psychological consciousness” [4, page 26]. This has been described as having the properties of wakefulness, reportability, self-consciousness, attention, voluntary control and knowledge.
In principle, access consciousness could, without much controversy, be ascribed to a computer system. A computer has memory, it has processors which can make use of the data stored in memory, it has output ports through which actions can follow. With modern technology, one of these outputs could, without much difficulty, be speech. Therefore, by Block's definition, it has access consciousness. As such, there are no conceptual problems introduced by this form of consciousness.
Access consciousness
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Phenomenal consciousness
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Relates to knowledge, function, intelligent information processing, sensory perception.
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Relates to experience, agency, “what is it like”
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Is observable by third parties and can be scientifically verified.
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Is only observable by the conscious subject. There is no way for a third party to know for sure that a subject has phenomenal consciousness (subjectivity).
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In living creatures, it has a clear and usually self-evident purpose and/or can be shown to give a survival advantage.
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There is no known survival advantage and, therefore, no known evolutionary driver for it to have developed.
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It is possible , at least in known principles, to build an intelligent robot which will be conscious of its surroundings in this sense.
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It is not known how phenomenal consciousness arises and therefore no way in which we can begin to design a robot which is conscious in this sense.
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An explanation of access consciousness constitutes an “easy problem” in the sense that it is known how to proceed even if it will take much research to obtain. It is amenable to the scientific method.
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An explanation of phenomenal consciousness constitutes a “hard problem” because it is not known where to start. Because the data is not publicly observable, the scientific method can be applied only, at best, indirectly.
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Access consciousness presents no conceptual or ontological problems. Phenomenal consciousness does and, indeed, is the basis of all questions.
[1] N. Block, “On a Confusion about a Function of Consciousness” , Behavioural and Brain Sciences, 18:227-47
[2] N. Block, “Concepts of Consciousness”, in “Philosophy of Mind, classical and contemporary readings”, Oxford University Press, 2002, ISBN 978-0-19-514581-6
[3] David Chalmers, Journal of Consciousness Studies 2 (3), 1995, pp. 200–219."Facing Up to the Problem of Consciousness"
[4] David Chalmers, “The conscious mind”, Oxford University Press, 1996, ISBN 978-0-19-511789-9
[6] B. A. Farrell, “Experience”, Mind, 59:170-98, 1950
[7] Thomas Nagal, “What is it like to be a bat”, Philosophical Review, 79:394-403, 1974
[8] Schrödinger, Erwin "The Mystery of Sensual Qualities" Chpt 6 of Mind and Matter (1958), in What is Life? with Mind and Matter and Autobiographical Sketches Cambridge University Press, Canto Edition (1992) ISBN 0521427088 p. 154.
[9] Broudy, H.S. Kierkegaard on indirect communication. The Journal of Philosophy, 58(9), April 1961, 225-233.
[10] Soren Kierkegaard, “Concluding Unscientific Postscript”
[11] Ian Ravenscroft,”Philosophy of mind, a beginner's guide”, Oxford University Press, 2005,ISBN 978 0-19-925254-1
[12] N. Block, “Consciousness”, in Gutenplan 1994
For this reason, investigation of access consciousness has been referred to, originally by Chalmers, as the (relatively) “easy problem”[3]. Even though not all the answers are known and there is much research left to be done, there is no reason to believe that answers cannot eventually be found.
Phenomenal consciousness
It is tricky, if not impossible, to define phenomenal consciousness and it is best illustrated by example. Consider someone who is watching a sunset. They certainly have knowledge which can immediately be used to prompt speech, reasoning and action, so the person is “access conscious”, or “aware” of the sunset. However, in addition to that, there is the experience of watching a sunset which goes beyond factual knowledge[6]. To use Nagal's description [7], there is “something it is like” to see a sunset. There is an appreciation of beauty, there might be a sense of peace and well-being or any number of similar feelings. In other words, there is an experience over and above the physical perception and this experience is something which is difficult, if not impossible, to communicate to others. This is akin to the well known problem of how to describe to a blind person what it is like to see red. It cannot be done [8]. Or if a person has never tasted Marmite the only way to describe what it tastes like is by reference to other tastes, such as salty and yeasty. It cannot be done outside the domain of tastes. A complete chemical description of Marmite would not help in describing the experience.
The subjective and essentially private aspect of phenomenal conscious experience is developed by Soren Kierkegaard who said "human existence is a mode of being in which subjectivity is the truth and [...] such truth cannot be communicated directly" [9, page 225] “Subjectivity is truth” [10].
These experiences, called “qualia” in the literature, are a characteristic of phenomenal consciousness and, although they are usually accompanied by access consciousness, they are not identical with it. It is certainly possible to have access consciousness without phenomenal consciousness as described above for the case of a computer. It is also possible to have phenomenal consciousness without access consciousness although, in humans, this is only likely to happen if there has been brain damage.
Unlike access consciousness, “phenomenal consciousness” has so far only been attributed to biological structures.
A comparison between these two types of consciousness is given in the table.