Noteworthy Excerpts
Consciousness Explained -- Daniel C. Dennett
Strong hallucination:
"One conclusion we can draw from this is that we are not brains in vats -- in case you were worried. Another conclusion it seems that we can draw form this is that strong hallucinations are simply impossible!* By a strong hallucination I mean a hallucination of an apparently concrete and persisting three-dimensional object in the real world -- as contrasted to flashes, geometric distortions, auras, afterimages, fleeting phantom-limb experiences, and other anomalous sensations. A strong hallucination would be, say, a ghost that talked back, that permitted you to touch it, that resisted with a sense of solidity, that cast a shadow, that was visible from any angle so that you might walk around it and see what its back looked like."
*In a nutshell, Dennett explains a philosophical game about a “brain in the vat”: a Higher Being takes a living, conscious brain to be suspended and adequately cared for within a container of fluid-what-have-you. He is able to stimulate the necessary neuron impulses to produce the effect of feeling, and is therefore hypothetically able to construct a subjective reality. Even if given infinite power, this is impossible because the amount of information needed to accurately convince the consciousness that its experiences are valid is, put mildly, beyond astronomical. All the variables that must be accounted for (perception of surroundings: the position and minute movements of the body, gravity, orientation, weight and atmospheric pressure, shifting of atmospheric pressure as the body moves, etc.) are too numerous to calculate, input, and return feedback in real time. There is invariably more trouble then, when given that every situation has limitless possibilities of development. The brain, in this situation, is like a computer which has a program that must be written as it is performed. Impossible? Even with infinite power to do so, hell yes. There is probably some fallacy of logic here, but this is getting to be a goddam huge nutshell. Moving on.
“Fleeting” or “weak” hallucination:
"[Similarly,] Descartes thought, since perceptions are caused by various complicated chains of events in the nervous system that lead eventually to the control center of the conscious mind, if one could intervene somewhere along the chain (anywhere on the optic nerve, for instance, between the eyeball and consciousness), tugging just right on the nerves would produce exactly the chain of events that would be caused by a normal, veridical perception of something, and this would produce, at the receiving end in the mind, exactly the effect of such a conscious perception."
Example: when an amputee experiences "phantom-limb sensation", he does not see or hear his missing limb, but feels that it itches, burns, moves, etc.
The hallucinator:
"[O]ne of the endemic features of hallucination reports is that the victim will comment on his or her rather unusual passivity in the face of the hallucination. Hallucinators usually just stand and marvel. Typically, they feel no desire to probe, challenge, or query, and take no steps to interact with the apparitions. It is likely, for the reasons we have just explored, that this passivity is not an inessential feature of hallucination but a necessary precondition for any moderately detailed and sustained hallucination to occur."
Consciousness Explained is a most excellent book. It lacks in humor that might otherwise enliven the whole affair, but Dennett's insight is beautifully and clearly expressed. Groovy. ♥
Strong hallucination:
"One conclusion we can draw from this is that we are not brains in vats -- in case you were worried. Another conclusion it seems that we can draw form this is that strong hallucinations are simply impossible!* By a strong hallucination I mean a hallucination of an apparently concrete and persisting three-dimensional object in the real world -- as contrasted to flashes, geometric distortions, auras, afterimages, fleeting phantom-limb experiences, and other anomalous sensations. A strong hallucination would be, say, a ghost that talked back, that permitted you to touch it, that resisted with a sense of solidity, that cast a shadow, that was visible from any angle so that you might walk around it and see what its back looked like."
*In a nutshell, Dennett explains a philosophical game about a “brain in the vat”: a Higher Being takes a living, conscious brain to be suspended and adequately cared for within a container of fluid-what-have-you. He is able to stimulate the necessary neuron impulses to produce the effect of feeling, and is therefore hypothetically able to construct a subjective reality. Even if given infinite power, this is impossible because the amount of information needed to accurately convince the consciousness that its experiences are valid is, put mildly, beyond astronomical. All the variables that must be accounted for (perception of surroundings: the position and minute movements of the body, gravity, orientation, weight and atmospheric pressure, shifting of atmospheric pressure as the body moves, etc.) are too numerous to calculate, input, and return feedback in real time. There is invariably more trouble then, when given that every situation has limitless possibilities of development. The brain, in this situation, is like a computer which has a program that must be written as it is performed. Impossible? Even with infinite power to do so, hell yes. There is probably some fallacy of logic here, but this is getting to be a goddam huge nutshell. Moving on.
“Fleeting” or “weak” hallucination:
"[Similarly,] Descartes thought, since perceptions are caused by various complicated chains of events in the nervous system that lead eventually to the control center of the conscious mind, if one could intervene somewhere along the chain (anywhere on the optic nerve, for instance, between the eyeball and consciousness), tugging just right on the nerves would produce exactly the chain of events that would be caused by a normal, veridical perception of something, and this would produce, at the receiving end in the mind, exactly the effect of such a conscious perception."
Example: when an amputee experiences "phantom-limb sensation", he does not see or hear his missing limb, but feels that it itches, burns, moves, etc.
The hallucinator:
"[O]ne of the endemic features of hallucination reports is that the victim will comment on his or her rather unusual passivity in the face of the hallucination. Hallucinators usually just stand and marvel. Typically, they feel no desire to probe, challenge, or query, and take no steps to interact with the apparitions. It is likely, for the reasons we have just explored, that this passivity is not an inessential feature of hallucination but a necessary precondition for any moderately detailed and sustained hallucination to occur."
Consciousness Explained is a most excellent book. It lacks in humor that might otherwise enliven the whole affair, but Dennett's insight is beautifully and clearly expressed. Groovy. ♥