Editor's comment

Patricia Smith Churchland is Chair of the Philosophy Dept. at UCSD. Her work relating recent brain studies with philosophy is extensive.

Reading on: Criticism of dualism

Churchland, Patricia Smith Brain-Wise: Studies in Neurophilosophy The MIT Press, Cambridge, MA 2002 [abridged – 230 words] – comments on the soul-brain hypothesis

In general, as a hypothesis about the nature of the mind, how does substance dualism stack up against physicalism? The short answer is that substance dualism chronically suffers from the lack of any positive description of the nature of the mental substance and any positive description of the interaction between the physical and the nonphysical. The content of the hypothesis is specified mainly by saying what the soul is not: that is, it is not physical, not electromagnetic, not causal, and so forth. Negative characterizations can be useful, and they may be fine as a place to start. Evaluation of the hypothesis cannot proceed, however, without some positive elaboration: we need to hear something about what the proposed interaction is, where the interactions occur, and under what general conditions. Were someone to proclaim a new theory of light that says only that light is not electromagnetic radiation, it would be difficult to know how to test it. Because the soul-brain hypothesis lacks a substantive, positive characterization, it too is hard to take seriously, especially at this stage of science.

The slow degeneration of memory and cognition generally seen in Alzheimer’s patients, for example, is currently explained within neuroscience as the progressive loss of neurons in the cortex. How, according to its adherents, might a soul-based story go? We are not told.