Are St. Thomas’ theories of the soul and its relationship to the person and the body still valid in the light of modern neuroscience?
St. Thomas was a great philosopher and you’d be hard pressed to find a contradiction in anything he wrote. Is it possible though that because he was working from a pre-scientific understanding of how the body works, he might have attributed natural processes to the ‘soul’. For example, intellect and will. Are these really properties of the soul, or are they merely the aggregation of hormones and other compounds like dopamine (will) in the brain?
On the contrary, modern science has actually been validating the position of St. Thomas Aquinas over and against that of recent materialists.
Just one example of this is the fact that if ideas were produced by the brain, you would expect the same, or at least very similar, brain patterns and chemical structures for the same idea. What we’ve discovered, however, is that two people’s brains work with the same “idea” and process very differently, even going so far as there being a fundamental difference in how men and women process the same ideas and information with different parts of the brain!
In short, there is no physical/chemical correspondence between the “idea” of a circle in your brain than there is in mine; the only thing they have in common is the “pure form” of circle.
This isn’t to say that brain damage doesn’t affect how we process information, but then even St. Thomas Aquinas understood that the state of the brain affects the non-material states of the brain. From the Summa Theologica I-84-7:
First of all because the
intellect, being a power that does not make use of a corporeal organ, would in no way be hindered in its act through the lesion of a corporeal organ, if for its act there were not required the act of some power that does make use of a corporeal organ. Now sense,
imagination and the other powers belonging to the sensitive part, make use of a corporeal organ. Wherefore it is clear that for the
intellect to understand actually, not only when it acquires fresh
knowledge, but also when it applies
knowledge already acquired, there is need for the act of the
imagination and of the other powers. For when the act of the
imagination is hindered by a lesion of the corporeal organ (my note: the brain), for instance in a case of frenzy; or when the act of the
memory is hindered, as in the case of lethargy, we see that a man is hindered from actually understanding things of which he had a previous
knowledge.
Here he is pointing out that even though the intellect’s operation is purely non-physical in itself (the understanding of pure ideas), the intellect makes use of the imaginative power of the soul in order to work with the “pure idea”. So our pure knowledge of “circle” doesn’t depend on the brain, but whenever we use that idea we also imagine it, which is the operation of the senses, and this occurs in the brain (by imagination) rather than the organs we received the initial impressions of “circle” from (for example the eyes in the case of its shape). Aquinas is saying that we may still have the pure idea of “circle” stored in our immaterial intellect, but we can’t process it properly without the unhindered working of the brain since the way we understand “circle” is by senses (or imagination, in the case of already-stored ideas).
Aquinas’ arguments for why the intellect and will must be non-material also still hold up, and great modern materialist thinkers have actually bumped into them directly in their own studies without having even read St. Thomas or other medieval philosophy. The most prominent of these is the materialist Dr. John Searle, who studies the theory of the mind, and who has poured a LOT of cold water over the notion of truly intelligent computers in recent years. The funny thing is that Searle DOES believe that the mind is purely material, but has discovered that the way it behaves is utterly unlike what we would expect from a purely material system. He simply believes that this is due to some materialistic causes that we don’t yet understand, and which couldn’t ever be replicated artificially, but what he’s discovered fits up
exactly with what Aquinas used when arguing for the immateriality of the intellect.
For an interesting read on this subject I recommend the thesis written by Br. Christopher Fadok O.P., a former student of Dr. John Searle.
opwest.org/Archive/2006/FadokThesis.doc
I’ve found that Aquinas’ arguments are a LOT more robust than I would have ever guessed. It’s a shame he’s not studied more outside of the Church, because he could really shed some much needed light on some of our modern gaps of understanding (as in the case of Searle, who admits he’s never read Aquinas!)
Peace and God bless!