In my understanding of the relationship between soul activity and brain activity, the case is not problematic for thomistic dualism.

I start from two notions:

a. Soul activity is supported by brain activity. The soul is bound or coupled to the brain.

b. The mapping of soul activity to brain activity is unique for each brain. Each soul-brain binding or coupling develops its own "Neural Activity-Thought Mapping Language" or NATML.

Thus, a particular mental image or abstract thought is mapped to a neural activity pattern in John's brain which is different from the pattern which maps that thought in Peter's brain. The patterns may differ in one or more of the following features:
- the number of neurons involved,
- the spatial (3-D) arrangement of the neurons,
- the path travelled by the electro-chemical signal between the neurons.

In the case of these twins, since their brains are highly connected, forming a system which could be called a hyperbrain, their souls have developed either identical or at least mutually intelligible hardware mapping languages, so that the neural activity pattern that maps any thought, concrete or abstract, is either the same for both souls or is mutually intelligible, with the result in either case that their souls can communicate via the hardware layer.

The case of mutually intelligible NATML's can result from each soul having exclusive "write" right in its own hyperbrain volume and both souls having "read" right in the whole volume. Thus, when twin A sees a dog, she generates or "writes" a specific neural activity pattern in her own volume. Since twin B can "read" that neural activity pattern, she learns that it means "dog" for twin A, because twin B is also seeing the dog. Later on, when twin A just thinks of a dog, she generates the corresponding neural activity pattern, which twin B can "read" and decode correctly.

The case of identical NATML's can result from both souls being able to "write" to the same hyperbrain volume.

In summary, when one soul thinks any thought, concrete or abstract, it "writes" a neural activity pattern which the other sould can "read" - because both souls are bound or coupled to the same hyperbrain - and understand correctly - because both bindings use either identical or at least mutually intelligible NATML's.
 

Last edited by Johannes (1/17/2018 8:31 pm)

As for apparently making empirical tests to prove or disprove the metaphysical (and thus supra-scientific) view of Thomistic dualism / hylomorphism, I think there's an obvious method here.


If the twins really did share an intellect, then they would be unable to individually and freely contemplate a form without the other twin also contemplating it at the same time. One of them could look at a triangle and be asked what all triangles have in common and thus contemplate the universal form of triangularity, while the other could look at a square and contemplate what all squares have in common and thus receive the universal form of squareness, and if they didn't have two seperate intellects, they wouldn't be able to do that and would either be forced to receive the form of another geometrical object as well or be forced to contemplate the form of the first twin who starts the contemplation without being free to contemplate a different one.


Of course, there is the fact that they share all material thoughts and images and can even see through each other's eyes, but this doesn't seem to present much of a problem because everyone else has the capacity to look at a picture of both a triangle and square and decide to contemplate only the form of the triangle rather than the square, and even keep the square in one's imagination without abstracting from it by force of will.


But as far as we can see, the twins don't seem to have any problems when it comes to thinking about forms individually and on their own accord, so right of the bat such a simple insight could be used to defuse this craniopagus example as an apparent problem for hylomorphists.

And also, if they did share intellect, then we could likely expect problems with the use of language since one of the twins would be focusing on one proposition or thought with the exclusion of all other propositions that would need a seperate intellect to be used, which would mean the other twin would either think the same proposition without thinking any other or would be forced to abandon a contemplation in favour of another.


And that's without even including any of the more extraordinary explanations that could be used by the Thomist if the twins did have equal mathematical prowess or such apparently problematic things, such as telepathy, or something similar to how angelic intellects can instantly share thoughts with one another. 

 

Last edited by aftermathemat (1/22/2018 2:31 pm)

Johannes wrote:

Yes.

What about the experiment I described above, where the twins, if they share one intellect, would be unable to independently grasp particular forms and would instead either be forced to grasp a form they don't want to along with the form they already decide to grasp, or would even be completely overriden and be forced to grasp the form the other twin is grasping without freedom for an independent act of intellection?


If such a thing were recorded, would this affect hylomorphism? Or is such an idea prima facie implausible with the evidence we already have of the twins living a normal life, because if someone had a non-free intellect that was dependent upon their fellow twin on occasion, then this would entail all sorts of extreme difficulties with thought and speaking that are simply not present?