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Visual hallucinations present a unique problem for ontology. On the one hand they are clearly not sense data, meaning they are not the phenomenal product of a transduced pattern of photons. On the other their emergence into awareness may create the subjective sense that this is the case. Hallucinations therefore are subjective (mind dependent) phenomena which are subjectively (phenomenally) experienced as objective phenomena. The basis for the seperation of experiences into the categories of real and hallucinated phenomena typically rests on the idea of origin. If an object in experience is intersubjectively verifiable as the cause of a visual experience, it is real, if not, it is a hallucination. This criteria is problematic. Both cases are produced by occurences outside awareness. Abnormal firing patterns and rates of action potentials in the visual cortex are as independent of intention and awareness as real world objects. This means The cause in both cases are mind-independent events. (To anticipate 1 criticism this is not really contentious, if you took the top off your skull and had a mirror the object you would see would be there regardless of your perception of it, and therefore so too must be the case when it's doing its thing with your skull intact)

The extended mind hypothesis proposes that the reduction of the mind to the contents of the skull is a mistake. In explaining this idea, Chalmers and Clark assert that in purely functional terms, a feedback loop from awareness to a piece of paper with information on it is identical to a feedback loop going from awareness to the activation of a distributed pattern of cells determined by connection wieghts between neurons, (being where memory is 'stored'). Similarly, using a calculator is, in a purely functional sense, the same as using the relevant neural structures, computation just happens in a different place.

My question, (yes it's coming..) is that does the existence of visual hallucinations throw a spanner in the works of the line of argument used to support the extended mind hypothesis? Feedback loops going from awareness to real world objects and back again are, in the same way as the examples of the paper feedback loop and the calculator feedback loop, functionally identical to feedback loops going from awareness to abnormal activity within the brain.

If extended mind hypothesis asserts no essential difference between these feedback loops:

(awareness) - (calculator) - (awareness) and (awareness) - (relevant neural activity for computation) - (awareness)

must we also then say that in visual perception

(awareness) - (physical object) - (awareness)

is the same as

(awareness) - (relevant abnormal neural states producing hallucinations) - (awareness)

meaning ontologically, for those subscribing to the extended mind hypothesis, hallucinations must be as real as real world objects.

Is this a problem for the extended mind?

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  • Interesting question. Would optical illusions also count?
    – draks ...
    Jun 14, 2012 at 20:16
  • the original question related to the fact that hallucinations (as events) are from the perspective of TEM as real as ordinary visual sense data, asking whether this is a problem for the model of the mind advanced in TEM theory. The case of optical illusions are indeed very interesting .. after reconsidering my position it would be hard i think for me to say yes
    – Dr Sister
    Jun 15, 2012 at 7:20

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Visual hallucinations present a unique problem for ontology.

Not really. In fact, the entire discipline of phenomenology is predicated on the notion that one can bracket the distinction between a visual hallucination and a veridical act of seeing.

Furthermore, ontology needs to deal with all kinds of entities that don't exist in the material world, so hallucinations are in no way unique.

The extended mind hypothesis proposes that the reduction of the mind to the contents of the skull is a mistake.

That's true, but remember that the extended mind hypothesis is in no way unique in proposing that; there are a number of philosophies which come to a similar conclusion by means of different manners of reasoning.

ontologically, for those subscribing to the extended mind hypothesis, hallucinations must be as real as real world objects.

No-- it means that from a phenomenological perspective, the cognition is the same.

In classical Indian philosophy, the canonical example given is that of mistaking a coiled rope for a snake. One looks and sees a snake, and later one looks again and realizes that it was not a snake at all, but a coiled rope. The two perceptions have the same status with regard to the mind, they are experienced the same; one happens to be veridical, and points to an external object which exists in the material world, and one points to a presumed external object which is not actually present in the material world.

In other words, the snake exists as a perception, but does not exist materially.

Is this a problem for the extended mind?

Not as I see it.

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  • I appreciate the reply :) .. i agree "from a phenomenological perspective, the cognition is the same." however i'm not saying that a hallucination is an object, only that as an event in the world, because its causes are as independent of awareness as an object, that it must be awarded the same ontological status, it's not to do with the meaning associated with it.
    – Dr Sister
    Jun 14, 2012 at 11:40
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    Correct; the event of cognition has the same ontological status in both cases-- but then, so would an act of imagination; I can imagine the Eiffel Tower, even though it is larger than my skull. The real Eiffel Tower and the imagined Eiffel Tower exist in different ways, but the perception of either of them has the same ontological status (i.e., that of an mental event.)
    – Michael Dorfman
    Jun 14, 2012 at 11:50
  • interesting thoughts .. the difference with imagination though is that it is a deliberate evocation, with hallucinations there is no intention involved, it's involuntary, and its cause is external to awareness. also "the perception of either of them [seeing and imagining the Eiffel Tower] has the same ontological status (i.e., that of an mental event.)" - do imagined events really have the same status as sensory phenomena? they're both events in the world, yes, but i can't eat an imaginary apple ..
    – Dr Sister
    Jun 14, 2012 at 12:24
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    You can't eat an imaginary apple, and you can't eat the apple you remember seeing yesterday, either-- but we're not talking about eating, we're talking about cognition. I think you ought to take a look at some phenomenology, if you are interested in these ideas.
    – Michael Dorfman
    Jun 14, 2012 at 14:24
  • having considered this more i think you're right. TEM is a conceptual model of the mind, not a methodology. Assuming its veracity doesn't preclude the use of phenomenological reasoning
    – Dr Sister
    Jun 15, 2012 at 1:35

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