Neuropsychology and personalist dualism: a few remarks

Titus Rivas, September/October 2004

It is sometimes claimed that personalist Neo-Cartesian Dualism as a serious philosophical candidate within the mind-body debate may be declared 'dead'. (See for example this paper by Keith Augustine.) The experimental and clinical findings of neuropsychology would unequivocally show that the brain is the sole cause and source of consciousness and cognition. However, the only thing that these findings really show is that the mind may to a large extent be influenced by the brain. In fact, this insight is not only compatible with Neo-Cartesian Dualism, it is an intrinsic aspect of this theory!

(Here's an article about a contemporary neurologist interested in dualism.)

Anti-dualists seem very fond of confusing the predicate "being influenced by" with "being existentially dependent on". If they were right, the very same would have to hold for the brain. As I showed elsewhere, from a logical point of view the brain simply must be influenced by consciousness (subjectivity), unless we wish to believe that consciousness does not exist. So if influence really equals dependence, this would suggest that the brain is dependent on consciousness for its very existence. However, -outside the peculiar Buddhist theory of complete interdependence- they obviousy cannot both be equally dependent on each other for their existence. In other words, influence does not equal dependence!

There is one subfield of neurology that seems less obviously irrelevant: experiments with split-brain patients which at first sight may appear to show that within an experimental context they possess two separate streams of consciousness. If this interpretation were the only one possible, substance dualism would be in serious trouble (it would certainly not discredit personalist dualism in general by the way, as it might be reconciled with emergent semi-substantialist dualism as defended by Karl Popper). However, there is a lot of debate about this issue, and there is no general consensus that the data should inevitably be explained in this manner. As John Beloff (whose dualism might be less personalist than mine) remarked in a paper about dualism, during these experiments one of the apparently conscious streams of consciousness may simply be subconscious (i.e. mentally active, but at a non-conscious level). The phenomenon would presumably be caused by the peculiar experimental setting which makes the simultaneous conscious integration of all the data into one total picture impossible. The fact that subconscious processing is allowed to express itself through one of the hands may be due to the experimental setting as well, or else it might be related to a lower level of inhibition by consciousness of motoric expressions based on mental, non-conscious processing (perhaps functionally comparable to the strange exclamations of patients suffering from the Gilles de la Tourette-syndrome, expressions which may be humorous and to the point but which are not usually seen as based on conscious thought either). The personal self would consciously be aware of only one part of the perceptual data and the rest of the information would reach its subconscious mind. The process would be comparable to other settings such as subliminal perception, blindsight and automatic writing, in that there would be a lot of parallel cognitive processing going on, but exclusively at a subconscious (or non-conscious) level rather than by (or through) a presumed co-consciousness. As we can also see in those other cases, this type of processing may be a lot more complex and intentional than what we would expect of a 'blind', mindless automaton, but there is no reason to suppose that it also has to be conscious (in the sense of subjectively experienced by a subject). It is certainly wrong to suppose that subjectivity has absolutely no impact on the brain (as is claimed in epiphenomenalism and other forms of physicalism) but it is also wrong to believe that all 'creative' cognitive processing and responses must inevitably be caused by consciousness, unless we wish to confuse two very different meanings of the word conscious, i.e. (cognitively, but not necessarily subjectively) aware and subjectively experienced (in other words: specifically subjectively aware).

We know from psychological and psychiatric literature that people may develop subconscious personality structures and it is enough to conclude that part of the perceptual information presented in split-brain experiments cannot reach consciousness though it is still processed and acted upon on a subconscious level, by a subconscious part of the person's personality. So there would be no creation of a new, separate mind or self (in the sense of conscious subject), but it would simply be another (rather limited) example of a cerebral impact on the mental activity of a substantial personal self, namely a limited impact on the integration of perceptual data in consciousness during specific experiments. Results of split-brain experiments would remain special in other respects, but not in the sense that they would prove the supposed divisibility of the self.
The subsequent processing of the data that are not accessed consciously does not have to be influenced directly by the condition of split-brain. It is more parsimonious to assume that as the data are not (rather than separately) perceived consciously, their further cognitive elaboration, and any motor response following from this, is shielded from consciousness as well. This would also explain unexpected emotional responses and the release of repressed wishes, attitudes, styles of communication, etc. through the (part of the) motor apparatus linked to the (non-dominant) hemisphere that is (during these experiments) not directly, interactively associated with consciousness. We already know very similar phenomena from the field of automatic writing in persons who have not undergone a commisurectomy. Parts of these subconscious characteristics do not need to have been created by splitting the brain, but they may have been present a lot longer. We do not have to embrace psychoanalytic theory to accept that a lot of our psychological structure normally does not reach the surface of consciousness.

It is rather amusing to see how some theorists think they can prove the presence of consciousness just by pointing to complex verbal responses or the manifestation of unusual attitudes. Both are rather thoroughly covered in the literature on subconscious processes. If these theorists were right, there would be no philosophical problem of the presence of consciousness in others. This can only be true if the existence of complex or verbal subconscious processing is excluded a priori! Again, epiphenomenalism and physicalism are very wrong, but that is not to say that we should ignore all the evidence for subconscious (or non-conscious) mental processing.

By the way, the 'hunches' some subjects may have about data that are not consciously perceived, do not have to be explained by the mysterious transmission of ideas through remaining nervous pathways, but it is sufficient to simply see them as messages from the subconscious mind which remains as much part of the mental life of the self as before.
Summing up, if one accepts the reality of subconscious mental processes, as is widely done in Neo-Cartesianism, there is nothing about split-brain experiments that would constitute a serious threat to personalist substantialist dualism. In fact, substantialist dualism even offers a plausible explanation for the finding that most split-brain persons seem perfectly normal and integrated. They remain one and the same person, though some of their (own) mentation becomes (at least temporarily) inaccessible to consciousness.

If anyone seriously wishes to entertain the position that split-brain does create two conscious minds, he or she should realise the following:

Not even if we accepted a non-substantialist interpretation in terms of the production of a new self by commisurectomy, would this imply that a 'self' in the sense of subject could itself (rather than its mind) be divided into more selves. We would 'only' have to accept that dividing the two hemispheres somehow creates a self. The self or experient (as such) should continue to be seen as indivisible, because how could one experient be literally divided into more than one experient! So the creation of a self should be a creation out of nothing (ex nihilo), as it is not created from the original self (there can be no Adam's rib in this context) nor from the stuff the brain is made of. This is a very problematic concept which cannot possibly be associated with a material system such as the brain. So much for the debunking of the indivisibility-claim of substantialism.

Future developments?
The topic of split-brain is sometimes used in futuristic thought experiments involving the consequences for personal identity of brain transplants of one hemisphere. Usually, these experiments seem to start from materialist interpretations of split-brain data.

It is possible that in the foreseeable future some of these experiments may actually be carried out in practice. What would it imply if the severed hemispheres would survive separately and if they would apparently both be related to a separate personality? Strange as this may seem, such experiments would not prove anything either. First of all, we should not forget that unless we would ascribe spatial dimensions to the non-physical self, the link between a brain or hemisphere and a non-physical self cannot be spatial in any literal sense. This means that the self may continue to interact with the two hemispheres, even if these are completely separated spatially (i.e. to a larger extent than by commisurectomy). As I said before, there can be no full-proof empirical demonstration of the presence of consciousness linked to any physical system (except if we see our own introspection as such a demonstration in our own individual case). Thus, there can never be any type of experiment that would show that splitting the brain really implies creation of a new conscious self. It will for ever remain an ontological question and cannot be determined empirically.

Dualism is very much alive and kicking! Let's concentrate on making it (even) more sophisticated. I invite any theorist who would like to elaborate upon these remarks to contact me.

Titus Rivas, September/October 2004


Here's a paper I find quite interesting for its views on split-brain, though it implictly starts from a position the author calls Cartesian materialism: Peter Ells: The Decider System Model: A Defense of the Cartesian Theatre 

Two other important papers: -