Sunday, December 19, 2010

Thomas Aquinas's Neuroscience of the Soul

One of my graduate students--Paul Vasholz--is writing a dissertation that argues for the compatibility of free will with modern neuroscience. In developing his argument, he builds on the work of Walter J. Freeman, a neuroscientist who defends the reality of human freedom, while also showing how neuroscience supports Thomas Aquinas's philosophical psychology.

Freeman's research has led him to formulate what he calls "nonlinear brain dynamics" as an alternative to the linear causality that is assumed in much neuroscientific research. Moreover, he argues, this nonlinear brain dynamics supports Aquinas's teaching about the unity of mind, brain, and body. Freeman's position catches my interest, because it seems to sustain my argument about the emergent evolution of the soul in the brain and the freedom of the human soul as the product of that emergent evolution.

For Freeman, the key question is whether perception is passive or active. While Plato views perception as a passive acceptance of eternal forms or ideas, Aristotle views perception as an active exploration of the world. Aquinas follows Aristotle in explaining perception as an active process of assimilation. The body does not absorb stimuli, but rather it changes its own form to grasp those aspects of the stimuli that are relevant to the goals in the brain. Knowledge is not driven by external powers, as suggested by Plato, but rather knowledge is driven by the brain's internal strivings and ends, as we explore the world and, by trial and error, assimilate ourselves to our physical and social world in a manner that satisfies our desires.

But then where do these self-generated actions into the world--our strivings to search and observe the world--come from? Aquinas's answer is that the ultimate source of our striving is nature and nature's God. Freeman's answer is that the ultimate source is natural evolution. Through evolutionary history, human beings have inherited a natural set of desires or inclinations that guide their intentional behavior.

I agree with Freeman that there is much in Aquinas's philosophical psychology that supports this understanding of the emergent evolution of the soul or mind as the activity of the brain. But Freeman fails to confront the incoherence in Aquinas's reasoning on this point, which manifests a fundamental problem in Aquinas's Aristotelian science of human nature. This is not just a problem for Aquinas, but a general problem in reconciling Biblical religion and evolutionary science. (See Freeman's "Nonlinear Brain Dynamics and Intention According to Aquinas," pp. 211-12, 211, 230-31, 233.)

The problem is the incoherence in both affirming and denying a radical dualism of body and mind. On the one hand, Aquinas agrees with Aristotle's biological psychology that the mind is the form of the living body, and thus mind and body are inseparable, so that the death of the body is the death of the mind. On the other hand, Aquinas's commitment to the Christian teaching about the afterlife forces him to say that the human mind or soul is immaterial and thus capable of existing without the living body supporting it. The situation becomes even more confusing when we see that Aquinas's commitment to the Christian teaching about the resurrection of the body forces him to say that the human mind or soul cannot exist in its perfection unless it is the activity of a living body.

Aquinas recognizes that in adopting Aristotle's biological psychology, he has to reject Plato's dualistic psychology. For Plato, the immortal soul rules over the mortal body like a pilot of a ship, and thus the soul can live on after the death of the body. Many early Christians (like Augustine) saw this Platonic dualism as the closest pagan approximation to Christian theology. After all, Plato's dialogues offer elaborate arguments for the immortality of the soul in an afterlife with eternal rewards and punishments. Plato's Timaeus looks enough like Biblical creationism that it became the primary text for medieval Christian cosmology. And yet orthodox Christians cannot be Platonic dualists, because Christians must believe in the resurrection of the body in the afterlife, which suggests that the perfection of the soul depends on the body. Moreover, Aristotle's criticism of Plato's theory of the eternal Ideas, with its dualism of mind and body, and Aristotle's teaching that the mind is the functional activity of the body denies Platonic dualism.

To defend the doctrine of the resurrection of bodies to eternal life, Aquinas thinks he needs to reject Platonic dualism and embrace Aristotelian mind-body unity. But it's not at all clear that an Aristotelian biological psychology can allow for living bodies to become immortal. Moreover, traditional Christian doctrine teaches that there's a period between death and resurrection in which human souls exist without bodies, just as angels exist without bodies. But it's hard to see how this is reconcilable with the inseparable unity of mind and body.

Aquinas is thus caught in a contradiction. He must say that "the soul is the form of the animated body," and "forms dependent in being upon matter do not themselves have being properly, but being properly belongs to the composites through their forms" (Summa Contra Gentiles, II, 51, 57). This would be compatible with neuroscientific research showing that the mind is the emergent activity of the brain. But then Aquinas also says that the human mind is an immaterial form that is not necessarily the form of a living material body. This suggests a radical dualism contrary to neuroscience.

The confusion is deepened, however, when Aquinas teaches that since "the soul is united to the body as form to matter," the perfection of the soul after the death of the body requires a resurrection of the body and its reunion with the soul. Thus must be so, because "the state of the soul in the body is more perfect than outside the body" (Summa Theologica, suppl., q. 75, a. 1).

Furthermore, according to Aquinas, this resurrected body must be a real living body. And since all living bodies are ageing bodies, the resurrected bodies must have a specific age. Since Jesus rose again at about age 30, that age must be the perfect age for the body, and so, Aquinas reasons, when human beings are resurrected, they will all have bodies of the same age--30 years old. Those who died as children will be moved up to age 30, and those who died in old age will be moved back to age 30 (ST, suppl., q. 81, a. 1).

But then we must wonder, when people wish for immortality, is this what they're wishing for--to be frozen eternally at one moment in time?

Shouldn't we say that this kind of immortality would be death?

Some related posts can be found here, here, here, here, here, here, here, here, here, here, here, and here.


Troy Camplin said...

Some fun thoughts. The immortality of the soul is a Platonist idea and was attached to Christian theology, but does not have a Biblical basis. The New Testament promise is thus of resurrection. If we truly discard the Platonist elements, we solve the soul-separate-from-the-body contradiction. We are left with a soul/mind emergent from the actions of the embodied brain, thus fully material and fully mind simultaneously. (Interesting how this problem is solved by becoming more strictly Biblical.)

Now, even if we assume Aquinas' vision of our being "frozen" at 30, that would be an un-aging, not an unchanging 30. Complex adaptive systems have to change to maintain their form, but they do not have to age (think bacteria). One could thus maintain bodily and mental form through change without having to age.

Anonymous said...

Perhaps this addresses the issue somewhat: