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?