If the logic of the EA (given in the previous post) is valid, then only if either (i) or (ii) is incorrect, is there potentially room to develop a theory of MC. So any theory of MC that attempts to meet “Kim’s challenge” must explicitly state which premise, (i) and/or (ii), is incorrect.
To begin with, note that without the sufficiency of c, Kim cannot apply the “exclusion of over-determination” principle, so cannot rule out mental causation on the basis of the EA. The sufficiency of c is crucial if the EA is to succeed at excluding MC.
In my book and on this blog last in Oct. 2013 I argued that the EA does not hold under indeterminism. I will repeat the argument again here because I think it is a necessary part of the foundation for everything I later want to say about how MC (including volitional MEs associated with FW) and downward causation work in the brain. If I am wrong about there being an escape from Kim’s logical headlock, the foundation of the house of MC I want to build collapses. That is, if the EA also holds under indeterminism, then MC, FW and MR are ruled out, period, and I would have to become a hard incompatibilist, whether determinism or indeterminism is the case. Is there an escape from such a bleak worldview?
Here goes. Premise (ii) does not hold if indeterminism is the case, because any particular present microphysical state is not necessitated by its antecedent microphysical state or states. In other words the traditional definition of causal closure that “every physical event has an immediately antecedent sufficient physical cause” is not satisfied, because when a cause c can be indeterministically followed by any number of possible effects ei, then c is not a sufficient cause of any of the possible ei, because they might not happen if they have not yet happened, and they might not have happened even after they have happened.
Classical deterministic laws are laws that apply among sufficiently causal actualia, where both c at t1 and e at t2 are actual events. Quantum mechanical laws are instead deterministic at the level of possibilia, but indeterministic at the level of actualia, because which possible outcome will occur upon measurement is only probabilistically specifiable. Nonetheless, under quantum mechanics c is sufficiently causal of its entire set of possible outcomes ei with their associated probabilities of occurring. It is just that c is not a sufficient cause of any particular one of its many possible effects that happens to happen when measured. Classical deterministic and modern quantum mechanical laws both operate deterministically, and causation is sufficient, but over different types of physical entities. Actualia and possibilia, while both physical, have mutually exclusive properties. Actualia are real and exist now or in some past moment; they have a probability of 1 of happening or having happened. Possibilia are not yet real and may never become real, and exist in the future relative to some c, and have a probability of happening between zero and one. A given event cannot be both actual and possible at the same time.
Closure, therefore, applies to different types of physical events under ontological determinism and indeterminism. “Closure” entails that the set of physical events is closed; Any particular effect will be a member of the same set to which a sufficient cause itself belongs. Determinism is closed at the level of actualia; Any particular cause or effect will be a member of the set of all actual events in the universe across all time. Indeterminism, in contrast, is not closed at the level of actualia because a non-sufficient actual cause and one of its possible outcomes that may never happen are not both members of the set of actualia. Rather, quantum theory is closed (and deterministic) at the level of possibilia: Any particular outcome or event will be a member of the set of all possible outcomes or events in the universe across all time, and any possible cause is sufficient to account for the set of all of its possible effects. Under indeterminism physical explanations are of a different type than under determinism, though both actualia and possibilia are physical, and theories of either are physical explanations.
An indeterministic causal closure thesis could be restated as follows: “(ii*) the set of all possible microphysical states is completely diachronically necessitated by antecedent possible microphysical states.” The realization thesis for the indeterministic case might be: “(i*) all mental states are synchronically determined by underlying sets of possible microphysical states.” But claim (i*) is contrary to the definition of supervenience. Mental events do not supervene on sets of possible physical states, they supervene on specific, actually occurring physical states. Since it is absurd to maintain that mental events synchronically supervene on sets of possibilia, we can rule (i*) out. It remains to be shown whether (i), i.e. supervenience on actualia, can be combined with (ii*), i.e. causal sufficiency and closure among possibilia, to yield (iii).
An actual microphysical state and the set of all possible microphysical states are different kinds with mutually exclusive properties (e.g., real/~real; present/~present). The essentially syllogistic structure of the exclusion argument requires staying within a logical kind. It is logically valid to draw from the major premise (ii) ‘All physical events are caused by preceding sufficient physical causes’ and the minor premise (i) ‘mental events are realized in physical events’ the conclusion (iii) that ‘the physical events that realize mental events have preceding sufficient physical causes’. But now we are splitting ‘physical’ into two types with mutually exclusive properties, possibilia and actualia. The conclusion (iii) of the syllogism holds only if both the major and minor premises hold and are both are about actualia as in (ii) and (i), or both are about possibilia as in (ii*) and (i*). If one premise is about possibilia and the other about actualia, the conclusion does not follow, because the premises are about exclusive entities. For example, (ii) and (i*) would read ‘All actual physical events are caused by preceding sufficient actual physical causes’ and ‘mental events are realized in sets of possible physical events,’ which violates syllogistic logic as much as ‘all men are mortal’ and ‘Socrates is a robot’. Conversely, (ii*) and (i) would read ‘The set of possible physical events are caused by preceding sufficient possible physical causes’ and ‘mental events are realized in actual physical events,’ which similarly violates syllogistic logical form.
In conclusion, if determinism is the case, then the EA holds, and MC, FW and MR are ruled out, as is compatibilism. However, if indeterminism is the case, the EA does not hold and MC and FW and MR are not logically ruled out, at least by the EA.
This still leaves open the hard work of explaining how MC might work in a brain that harnesses indeterministic events to make information downwardly causal, which I will take up in my next post on downward causation.