At a talk I gave this weekend, a man in the audience (a psychiatrist, actually) took an interactionist view of the mind: he said that while the brain could certainly influence the mind, the reverse was also true: mind can causally influence the brain. I failed at the time to convince him otherwise. I realize now that what I should have said was this: Can the wind influence air molecules?
Obviously, the wind IS air molecules. Nothing more. If one says that the wind influences air molecules, all one is really saying is that if a whole bunch of air molecules happen to be moving in some direction (that’s what we mean by “wind”), this motion will influence other air molecules. That is to say, air molecules influence each other, which is obviously true. Wind itself doesn’t have any existential status, let alone causal power, over and above its constituent parts.
To prove his point, the psychiatrist said that things like counseling can work better in some psychiatric conditions than medication. Fine. QED for top-down causation, he thought: a non-biological intervention influences biology. But how does counseling work? It involves talking. How does that talking make a difference to the listener and his or her brain? The sound from the talking goes in their ear, and that produces electrical activity in the auditory nerve, etc. If that sound is organized just right, the neurons processing it will influence other parts of the brain in such a way as to change emotion, or thought processes, or whatever. But at the end of the day, it’s neurons influencing other neurons. Moreover, what PRODUCED the talking, on the part of the counseling therapist, is their vocal apparatus, which is also controlled by their brain. So all we’re really seeing here is neurons affecting other neurons. (And neurons, of course, are similarly reducible into their constituent parts. Predictability, of course, is another matter, mostly because of nonlinear dynamics.) If one wants to refute that, the burden is to document a mental event that has no neural correlate (see also supervenience).
This whole episode reminds me strongly of the time a graduate student in English told me that Shakespeare was so much more that a sequence of letters. (She was railing against my delivery of the infinite monkeys scenario.) Excuse me? Shakespeare IS so much more? IS? What the hell are you talking about?
The psychiatrist’s argument about top-down causation sounds like reification, where abstractions are regarded as physical things.
Some systems don’t appear to be the sum of their parts, but just because we aren’t using linear combinations doesn’t mean the system is not reducible to it’s parts, addition is not the only combinatory operation.
It is like reification, except in that dualists like this gentleman would say, “no, no, the mind is NOT physical. But it is a real thing, and it can influence the brain.” Nonsense, for sure. As to the linearity thing, I think you’re right: most people have weak intuitions about how nonlinear systems act, and when they think of large systems, what they really think of is large LINEAR systems. And those don’t seem complex enough to produce the richly dynamic, self-modifying behaviors of, e.g. brain/minds. Another reason for stronger science and quantitative literacy.
So if the mind is not physical, but interacts with physical things, I would just say our previous use of the word “physical” needs to be expanded to include this new causal factor. But we’d need some conclusive demonstrations of superveiniance first.
It never ceases to amaze me how easily we can get unpredictability or structure from simple rules.
Having attended that conference, I think that the psychiatrist was just too threatened to accept your message.