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According to materialism, the conscious mind is the product of the brain. Thus, if the brain is split in half such that the two hemispheres cannot communicate with each other, then there are three possibilities:

  1. Both hemispheres gain their own conscious mind.
  2. Only one hemispheres has a conscious mind.
  3. A single conscious mind operates across both hemispheres.

Within a materialistic paradigm, #3 is impossible. There cannot be unified control without communication between the two hemispheres.

Option #1 is false according to this article,

A new research study contradicts the established view that so-called split-brain patients have a split consciousness. Instead, the researchers behind the study, led by UvA psychologist Yair Pinto, have found strong evidence showing that despite being characterised by little to no communication between the right and left brain hemispheres, split brain does not cause two independent conscious perceivers in one brain. Their results are published in the latest edition of the journal Brain.

and this answer.

So I conclude from [sic] this quick literature review that Joseph ascribes the presence of two minds based on something that can be explained at a more basic level, and hence by a more simple model, namely disinhibited motor control. Given the principle of parsimony, I conclude his observations were right, but that his conclusions were not.

Option #2 is false according to this answer. The answer state consciousness does not transfer to one half, but continues to operate in both halves.

If by continuity you mean, "a feeling that I am who I was before the operation, (perhaps with some changes)", then it seems that each hemisphere would separately maintain continuity, in the same way patients after massive strokes and other sudden brain injuries don't usually feel "they are a different person".

Thus, only option #3 is viable according to the available data.

If option #3 is indeed the only possible explanation, yet is impossible according to materialism, then the materialistic explanation for the conscious mind is false.

A fourth possibility is there is an alternative communication pathway that is not severed, as hinted at by this answer.

Keep in mind that there are many other pathways between the hemispheres besides the Corpus Callosum - such as thalamocortical circuits, those via the midbrain and brainstem and of course external sensorimotor feedback.

Is option #3 the only viable option, or do the halves somehow communicate in a different way?

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    $\begingroup$ "or some implicit premise is false" ... there are hundreds of underlying premises hidden in these statements which all will boil down to debating the nature of consciousness. For example: "If the two brain halves cannot communicate with each other, then the halves should generate two independent conscious minds"; why would this be so? This contains a hidden premise along the lines of "any subsection of the brain gives rise to a conscious mind". In short, no, your argument does not sound valid at all (thus does not disprove a materialistic mind). $\endgroup$ – Steven Jeuris Apr 18 '17 at 20:23
  • $\begingroup$ @StevenJeuris I've clarified the argument. $\endgroup$ – yters Apr 18 '17 at 21:10
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    $\begingroup$ Why isn't "4. There is no longer a conscious mind" in the list of options? Or a 'different' form of conscious mind, given that no clear definition of 'conscious mind' is given. $\endgroup$ – Steven Jeuris Apr 20 '17 at 7:26
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    $\begingroup$ Also, your exclusion for option 1 and option 2 seem to contradict each other no? So you are using different lines of reasoning to aggregate into one conclusion, further indicating there are unclear underlying premises which you have not defined and seem to contradict each other. More concretely, your reason for excluding option 2 also seems to exclude option 3, why do you decide to keep that one? That said, I feel there is sufficient information in this question now (albeit some erroneous reasoning) for this to be answered, thus I reopened. $\endgroup$ – Steven Jeuris Apr 20 '17 at 7:32
  • $\begingroup$ @StevenJeuris I should also add what a non-materialistic mind looks like. This means the mind resides in a non-physical realm, and somehow can interact with different parts of the brain independently. Thus, if the different brain parts can no longer communicate with each other, they can still all received communication from the same mind, and be synchronized under unified control. The result is that falsifying #2 provides evidence for #3 under this theory of mind. $\endgroup$ – yters Apr 20 '17 at 15:06
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The question title reads:

Does the split brain disprove a materialistic mind?

The simple answer being no, nothing disproves that - the brain harbors the mind e.g., (Lilienfeld & Arkowitz, 2008).

Now you mention that two hypotheses on split-brain patients are false, namely...

  1. Both [hemispheres] gain their own conscious mind.

  2. Only one [hemisphere] has a conscious mind.

...and I agree with them being incorrect hypotheses as suggested in the linked pages.

Now you proceed with...

[Does a] single conscious mind operates across both [hemispheres ?]

Importantly, you state yourself that...

[...] there are [...] other pathways between the hemispheres besides the corpus callosum - such as thalamocortical circuits [...] and those via the midbrain and brainstem [...].

So from my perspective, up until now you have answered your own question whether one single mind operates across two hemispheres in split-brain patients. Anyway, to illustrate some additional interhemispheric commissures besides the callosal pathway, see Fig. 1. This shows that 'split-brains are in fact not entirely split; only the main causeway is severed.

Now there are wild stories about split-brain patients having a dual consciousness, including the paper by Joseph (1998) where the author speculates that one of his patients "...was possessed of two minds" based on the frustrations experienced by this person because his motor skills were erratic. Andrew & Akelaitis (1945) explain that split-brain patients can display diagnostic dyspraxia by an unbalanced inhibitory influence of the dominant hemisphere over the non-dominant side, explaining the uncoordinated behavior on the non-dominant side. These symptoms generally diminish over time, as the brain deploys alternative inter-hemispheric routing of communications.

brain
Fig. 1. Interhemispheric pathways are indicated by numbers 1, 2, 3 and 4. source: Urbanski et al. (2014)

References
- Andrew & Akelaitis (1945) Am J Psychiatr; 101(5): 594-9
- Joseph, J Clin Psychol (1988); 44(5): 770-9
- Lilienfeld & Arkowitz, Sci Am Mind (February 2008)
- Urbanski et al., *Front Integr Neurosci (2014)

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    $\begingroup$ That alternate pathways are eventually established does not address the situation immediately after the brain is severed. If these pathways do not yet exist, yet the conscious mind is still unified across both halves, then this is evidence for an immaterial mind. $\endgroup$ – yters Apr 20 '17 at 15:09
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    $\begingroup$ @yters - they exist beforehand; it is thought additional links get established once severed. $\endgroup$ – AliceD Apr 20 '17 at 21:20
  • $\begingroup$ I mistyped. The second sentence should read: If these pathways are not yet established, yet the conscious mind is still unified across both halves, then this is evidence for an immaterial mind. $\endgroup$ – yters Apr 23 '17 at 0:06

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