Murphy argues that brain localization technology has demonstrated the truth of emergence over and against the idea that the soul unifies mental processes (perhaps the physical brain is the occasion of the soul’s unification of the human person?). For example, damage to certain parts of the brain can produce certain behavioral or cognitive abnormalities or dysfunctions, and we have, in many instances, localized the parts of the brain responsible for certain kinds of behaviors or cognitive functions through brain scans of brain-damaged patients.
She even criticizes the Thomistic understanding of the soul as a kind of life principle, replacing it with nenurological properties. Instead of the soul being responsible for intelelctual or symbolic functions, she correlates these functions with specific brain regions, and she uses DNA and neurochemicals to explain the activitiy of the nutritive soul. Ultimately, she argues that science has provided us with what Thomas wanted to provide, but was unable because he lacked the requisite brain scanning technology and knowledge of neuroscience.
Murphy argues that evolutionary history explains how the ability to love the transcendent God gradually emerges through physiological processes. These mental activities are governed in terms of higher-level laws made possible, as Jeffreys notes, through specific parts of the brain. Jeffreys notes that Murphy and Hasker both dispute the idea of a purely immaterial soul, particularly when it comes to the question of supervenience, since, Hasker argues, it is impossible for the mind to vary independently from the body. Indeed, neither can vary independently from the other, so closely bound up are the body and the mind. In the language of supervenience, we would articulate the dependence of the mind upon the body in terms of the impossibility of there being an A-difference without there being a corresponding B-difference.
However, a Thomistic understanding of the relation of the mind to the body entails understanding the importance of acknowledging the relation between the mind and the body. For Aquinas, the mind and body are intimately bound up with one another. The soul, for Aquinas, as Jeffreys notes, is defined precisely as the “form of the entire body and of each of its parts.” The soul, while it can exist apart from the body, for Aquinas, requires the body for many of its vital functions. Thus, the correlation between the functions of the mind and the states of the brain can be preserved without resorting to non-reductive physicalism. John Eccles, for example, a neuroscientist, appeals to his field in support of dualism, as Jeffreys notes. We can thus acknowledge how importantly bound up the mind is with the physical person, including the brain, without insisting that the human mind emerges metaphysically from the human brain.
Murphy believes that rather than seeing non-reductive physicalism as a philosophical thesis, we view it as a scientific theory, unified by the metaphysical thesis of non-reductive physicalism, as Jeffreys notes. He notes the circular nature of Murphy’s research program, since she is assuming its truth and then finding evidence for it scientifically, setting her up for confirmation bias. Instead, the notion of non-reductive physicalism needs to be attacked or defended philosophically; that is, assessed as a philosophical thesis, rather than as a scientific theory.
Jeffreys insists that non-reductive physicalism will not provide us with a successfully research program because he does not believe that it allows us to explain or understand the entirety of the human mind or soul, and that the reason it fails to do this is because it lacks an adequate understanding of causality. The non-reductive physicalist, such as Murphy, insists that the mental arises from the physical, but she does not explain how this is even possible. It is certainly a counterintuitive causal relation. How can something mental arise from the physical? How can evolution explain how inanimate objects produced animate objects which, after a sufficiently sophisticated evolutionary process has taken place, proved capable of having emotions and thoughts and beliefs and desires? Murphy, however, believes that in due time, science will provide us with answers to these questions, consistent with her belief that emergentism ought to be understood as a scientific theory rather than a philosophical thesis.
Jeffreys, Derek (2004). The Soul is Alive and Well:
Non-reductive Physicalism and Emergent Mental Properties. Theology and Science, Vol 2, No. 2, 2004 (dx.doi.org/10.1080/1474670042000261105 )