The fading qualia argument

@Claim C: There is a computer program that is logically sufficient for consciousness (when being executed).@

  • Distinguish between phenomenal consciousness and self-consciousness.
  • Mental states that are P-conscious = mental states with qualia = mental states with phenomenal / qualitative properties = states for which there is something it is like to have them = states which have a subjective feel
  • Emotions, perception, sensations are all P-conscious.

The argument

See section 3 of Chalmers (1995). Absent Qualia, Fading Qualia, Dancing Qualia. In Thomas Metzinger (ed.) Conscious Experience. Imprint Academic. See online paper at

The Thought experiment

Imagine that you are looking at a red wall, while your brain cells are replaced by functionally equivalent nano-computers one by one. What would happen to your qualia? Here are some possibilities:

  1. P-consciousness fades away gradually.
  2. P-consciousness disappears suddenly when a large number of neurons have been replaced.
  3. P-consciousness is still present.

Chalmers argues that there will not be any change to the qualia of the experience. This implies:

  • Functional (and therefore computational) organization is sufficient for qualia.
  • Neurophysiological properties not directly relevant to consciousness. Qualia can occur in non-biological systems.

@In any case, the conclusion is a strong one. It tells us that systems that duplicate our functional organization will be conscious even if they are made of silicon, constructed out of water-pipes, or instantiated in an entire population. The arguments in this paper can thus be seen as offering support to some of the ambitions of artificial intelligence. The arguments also make progress in constraining the principles in virtue of which consciousness depends on the physical. If successful, they show that biochemical and other non-organizational properties are at best indirectly relevant to the instantiation of experience, relevant only insofar as they play a role in determining functional organization.@


Objection #1: The subject might be radically mistaken about his lack of consciousness

  • We can be mistaken as to whether a certain conscious experience is present.
    • Anton's syndrome - A cortically blind subject strongly denies that he or she is blind in the face of clear evidence of their blindness, usually accompanied by confabulation. Typically resulting from brain damage occurring in the occipital lobe following a stroke or head injury.
  • Rejoinder: But those with Anton's syndrome suffer from problems with reasoning. This does not occur in the replacement operation.

Objection #2: Maybe consciousness does not exist

  • The argument shows that if we are conscious, then a functionally equivalent system must also be conscious.
  • But are we really conscious?
    • Some people argue that the concept of consciousness is confused and inconsistent. Consciousness does not really exist.

Objection #3: Maybe it is not possible to achieve functional equivalence through replacement

  • We have not done the experiment, so maybe FETR is not possible.