Bad news and worse than bad news for mental causation—this could be an alternative title of the book that I have just read. The real title is “Mind in a Physical World” by Jaegwon Kim. The book is a series of lectures that the author gave at the University of California in 1996. Fun fact: David Chalmers was the member of the audience. I wish I could be a fly on the wall at that moment.

The author bothers himself with the problem of mental causation. There is mental causation or there is no mental causation—this is how the problem could be formulated. Imagine you are having an itch, and you want to scratch it, and you scratch it. Is your wish to scratch an itch causing you to scratch the itch? In order to scratch an itch, your brain (namely, the motor region of your brain) needs to be activated. Thus, your wish to scratch an itch that activated your motor region. If it sounds like cartesian dualism, it is not exactly it. What I am trying to describe is supervenience. 

Let’s generalize. For any mental property M (M - for mental), there exists a physical base property P (P - for physical), such that M has P at time t, and if anything has P at t, it has M at t. This means that mental properties supervene on physical properties. Supervenience is a more relational concept that describes how mental properties depend on physical properties without implying that they are the same thing. Imagine two people with identical brain states (P). If supervenience holds, then they must also have identical mental experiences (M). However, this does not mean the mental experience is the same thing as the brain state.

Supervenies can be temporarily satisfactory, but it turns out that it doesn’t solve the problem of mental causation. If M supervenes on P, then M* supervenes on P*. However, if P causes P*, as things usually do in physical domain, then there is no additional work to be done by M. M only seemingly causes M*, while genuine causality is from P to P* (this argument is called the exclusion problem). Therefore, there is no mental causation.

Now, let’s look at the same argument but substitute mental and physical with macro and micro properties. Macroobjects in the world around us consist of microobjects, but properties that macroobjects have may be distinct from properties on microobjects. I will use an example of viscosity. Viscosity is a macroproperty of a liquid that describes its resistance to flow (e.g., honey is more viscous than water). It arises from the interactions of individual molecules. The individual molecules that make up the liquid follow physical laws, but they don’t have viscosity as an individual property. Therefore, it seems that viscosity have causal powers. Does it solve mental causation? The author believes that it doesn’t. 

The way to reconcile the issue and still remain physicalist is to come up with (or discover) so-called bridge laws. These laws are supposed to link second-order properties with their base properties. If a certain second-order property may be realized by multiple constellations of first-order properties, there could be a set of bridge laws to explain this. For instance, if different species have divergent mechanisms of attention (I do not claim they do, but if), then it is not a problem for bridge laws as there could be as many laws as needed. 

The problem, according to the author, is the lack of explanatory power in bridge laws. Why is it C-fibers activation that correlates with subjective pain? What specific property of C-fibers there is that can explain pain? And why is there pain at all when C-fibers are activated?

The solution that the author proposes is to make bridge laws functional identity laws. If now mental property M is defined in terms of its causal role and its causal effects, then physical property P meets the same causal specification. 

If you are lost at this point, I apologize. I’m lost as well. I was unable to reconstruct the whole chain of arguments. Many things were just left hanging in the air, and many things, for me, didn’t follow. Many questions were followed by more questions. Moreover, in the end, the author arrived at the conclusion that his reductionism is not good enough because some mental properties, like subjective experience of taste or smell, are not functional.

I may suggest reading the book simply to have food for thought.

Big revelation: Supervenience and emergentism are different things!

September, 2024