Darek Barefoot's argument from Mental Causation
Darek Barefoot, in response to some criticisms of my book by Richard Carrier, has developed a version of the argument from mental causation based on two corollaries of naturalism and two corollaries of reason. The corollaries of naturalism must be true if naturalism is true, the two corollaries of reason must be true if there is to be the sort of rational inference we find in the sciences.
The two corollaries of naturalism are:
1) To the extent that changes in natural systems have causes, those causes are potentially available to the senses either directly or by scientific instruments.
2) Every belief accompanies a natural (physical) state, and the properties of a belief are wholly dependent upon and determined by the natural state that it accompanies.
The two corollaries of reason are:
1) Reason includes, although it is not limited to, the acceptance of a belief due to the accurate, conscious perception that true premises logically entail it.
2) A belief may be considered to be held rationally only to the extent that what are consciously perceived by the holder to be the reasons for his accepting the belief are in fact the reasons for his doing so.
It should be noted that the corollaries of reason need not be true of all beliefs. We might believe some things non-inferentially because we perceive the objects in question. Thus, perhaps my belief that my glasses are one the table doesn’t require me to draw any inferences in order to be justified. If I have a hunch that Smith won’t betray my secret if I tell it to him, this may not have to be due to some traceable reasoning process. However, if we deny that there is rational inference of the kind that I have been talking about in this essay, which conforms to the two cited corollaries of reason, then the heart of science is ripped out. If physics is a true source of knowledge about the physical, then some people have to be able to draw precise mathematical inferences.
What lies at the heart of naturalism is the idea that the methods of science, of observation and measurement, can be applied to every type of reality. In the last analysis, everything is at least potentially available to the senses and can be analyzed in scientific terms. If there are features of reality that we can only reach through introspection, which in principle someone could not figure out looking at it from the outside, then something has escaped the nets of naturalistic analysis.
If a broadly materialist world-view is true, then only physical states can have any causal efficacy. If could provide necessary and sufficient conditions for propositional s states by specifying physical states, then we would be able to bring propositional contents into the web of causal interaction in a naturalistic world. However, the trouble is we cannot do that. The following is an adaptation of an argument Barefoot provides against the reconcilability of the corollaries of reason with the corollaries of naturalism.
1) Only the physical properties of representations can generate functional states in computational systems.
2) Propositional contents cannot be identified with the physical properties and their representations.
3) Therefore, propositional contents cannot generate functional states in computational systems.
4) Propositional contents generate some beliefs in some minds.
5) Therefore, some beliefs in minds cannot be identified with, or wholly dependent upon, functional states in computational systems.
I conclude, therefore that the problem of mental causation is still a serious difficulty for materialism, and failure to solve it calls into question the very scientific enterprise which alone provides the foundations for naturalism. We still haven’t got a good naturalistic answer to the question “Even if grounds do exist, what exactly have they got to do with belief as a psychological event.”