Downward Causation I

Lately I’ve been fiddling with a thought experiment that seems to suggest the causal efficacy of higher-level properties and objects, and have been wondering how such causal efficacy may be compatible with causal closure of the physical (more exactly microphysical) domain.  Since I am gullible and prone to make mistakes I present my half-baked ideas on these matters, in search of further criticism and illumination.   

As a non-reductive physicalist, I want to maintain the existence and causal efficacy of higher-level objects, properties, and events (that is, at levels higher than the microphysical).  And since I am also a physicalist, I am required to acknowledge the causal closure of the microphysical, i.e., that if a microphysical event has a cause, then it has a microphysical cause.  But there is a tension between these two positions: if higher level entities have non-redundant causal powers, then this leads to downward causation (the microphysical level is open to causal input from higher levels).  Downward causation, in turn, seems to violate the causal closure of the microphysical.  Kim‘s causal exclusion argument and Merricks‘s overdetermination argument exploit this tension in favor of reductive or eliminative physicalism. 

I believe that the tension ought to be resolved without giving up the causal efficacy of higher level entities.  Now I have a thought experiment which convinces me of their causal efficacy.  The basic idea behind the thought experiment is this.  Our social world is rife with conventions, and these conventions are arbitrary.  For instance, it is the convention everywhere to drive on one side of the road (right or left), but each country could just as well have adopted the alternative convention of driving on the other side of the road.  Hence the movements of hundreds of millions of car-wise arrangements of microparticles could have been vastly different.  This seems to indicate that our traffic conventions (in addition to microphysical laws) determine the movements of these microparticles, which is an instance of downward causation.

My thought experiment builds on the basic idea that the movements of microparticles this way or that way depend causally on the adoption of this or that rule of convention.  So, consider the game pieces on the chess board, moved about in accordance with the rules of chess.  These pieces are composed of microparticles, and the movements of these microparticles on the board are microphysical events which have microphysical causes.  Sure, these game pieces are moved about in accordance with the rules of chess.  But given the causal closure of the microphysical, the movements of the microparticles composing the pieces would be fully determined by the laws of microphysics. 

Now here’s the twist.  Take the game of kness, which is exactly like the game of chess, except that the knight can only jump over pawns (I suppose the clergy and the royalty might appreciate this rule).  Whenever we sit down to play a game of chess, we might decide to play kness instead.  And if we decide to play kness instead chess, everything else remaining the same up to the moment of the decision, then the movements of the knight-wise arranged atoms on the board would be systematically different from those in the game of chess. 

So, what accounts for this systematic difference between the kness game we play and the chess game we could have played in this scenario (and in the correspondingly different movements of knight-wise arranged atoms)?  It cannot be the laws of microphysics, since they remain the same regardless of whether we play in accordance with the rules of chess or kness.  It cannot be the initial positions, velocities, and other intrinsic/extrinsic properties of the microparticles at the start of the game, since we have stipulated these to be the same in our ceteris paribus clause, “everything else remaining the same”.  Therefore, the systematic difference can only be accounted for by the difference in the rules of chess and kness, which govern the movement of chess pieces.  These rules, when rigidly followed by the players, dictate the systematically differential movements of knight-wise arranged microparticles in kness as opposed to chess. 

Objection 1.  By now, of course, you will have noticed a gaping loophole in my ceteris paribus clause, which allows us to get around the conclusion just reached.  The physicalist who affirms the causal closure of the microphysical domain will surely insist that everything could not have remained the same up to the moment of our decision to play kness instead of chess.  There would have been differences in the microphysical states underlying the intention to play kness and the intention to play chess.  Moreover, the determinist would add that I am assuming, in that ceteris paribus clause, the libertarian position that free choice uninfluenced by physical causes and influencing physical events is possible.  This libertarian assumption begs the question against causal closure of the physical domain, and renders the argument in the previous paragraph circular.

My Response.  Now, I believe these physicalist responses are red herrings (I especially do not want to mix up the issue of the causal efficacy of higher level entities with the debate between determinists and libertarians on the free will).  The loophole can easily be mended, as follows.  Instead of human players, imagine two computers playing against one another in a room.  These are programmed to move about the game pieces on the board in accordance with the rules of chess or kness.  This eliminates the room for human error.  And let’s rig up the room to a setup like that of the Schroedinger’s Cat: a Stern-Gerlach device measures the spin of a quantum object in a superposition state, and according as the measured spin turns out to be up or down, the computers play chess or kness.  This allows us to get around the issue of human free choice.  Whether the computers play chess or kness depends on the probabilistic outcome of the measurement, everything else remaining the same up to the moment when the measurement takes place.  Then our old conclusion still stands.  The laws of microphysics and the initial states of the microparticles cannot account for the systematic difference in the movements of knight-wise arranged microparticles in chess and kness.  Only the different rules of chess and kness do that.  (There is, of course, a difference in the spin of the quantum object which triggers a game of kness as opposed to chess.  But this only explains why the computers play kness instead of chess.  It doesn’t explain the systematically different movements of knight-wise arranged microparticles in chess and kness.) 

In later posts in the same series, I hope to anticipate and address some further objections that a redutive physicalist is likely to make, and suggest a way of resolving the tension between causal closure and downward causation.  But quite likely I will face insurmountable objections.  So, more half-baked ideas on the way in the next few days!

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2 thoughts on “Downward Causation I

  1. Boram,

    Interesting thought experiment. It seems to me that the objections aren’t red herrings. And that your restatement of the thought experiments (involving computers and the Stern-Gerlach device) just pushes the problem back.

    It seems to me that the move to superimposed quantum states just assumes that the microphysical is not causally closed, and that is doing most of the work. You may respond that you intend by `closure’ to mean something compatible w/ quantum indeterminacy — perhaps it is to be cashed out by statistical or probablistic causal determinacy. Fair enough, but in *that* case, there is a physical difference which determines why the particles-arranged-knight-wise move the way they do — the probability of the given quantum particle being in a certain state.

    You say, “But this only explains why the computers play kness instead of chess. It doesn’t explain the systematically different movements of knight-wise arranged microparticles in chess and kness.”

    Okay, if we’re willing to grant that, then what does explain these movements? The rules of knees (or chess). But presumably in order to play either, those rules must have been programmed into the computers, and those programs involve microphysical states of the computer. So, the physicalist will probably say that those are the relevant causal explanation of the movements of the knights.

    I guess I’m still not seeing why the explanation *has* to be higher-order to make sense of the experiment.

  2. Aaron, nice. I mean especially the point you make on your second last paragraph. That’s one of the probably insurmountable objections I alluded to at the end of the post. I think I have some sort of response to it (involving multiple realization, among other things), but it will have to wait until tonight.

    As for your suggestion that “the move to superposed quantum states just assumes that the microphysical is not causally closed”. In response to that I can only say: of course causal closure has to take into account indeterminateness of quantum mechanics. But here we must follow Peter Kosso in distinguishing between “being in/determinate” (which is a static concept) and “being in/deterministic” (which is a dynamic concept).

    Namely, determinateness or indeterminateness has to do with the state of affairs at any given instant: if a property of a given thing has no definite value at a given instant, it is indeterminate. A superposed quantum state of up or down is indeterminate in this sense. Determinism or indeterminism has to do with the evolution of one state of affairs at one instant to another state of affairs at another instant, and determinism says that the second state of affairs is uniquely determined by the first (as per Kosso’s definition).

    Now, I distinguish causal closure from both being determinate and being deterministic. Causal closure of the microphysical, as I understand it, states that higher-level properties do not introduce new forces over and above the fundamental forces generated by microphysical properties. The kind of libertarianism that opposes causal closure would state that mental properties do introduce new forces over and above the fundamental forces of microphysics. The use of superposed quantum states in my thought experiment does not presuppose this sort of libertarianism, which is diametrically opposed to causal closure. So I think the computerized, Schroedinger’s Catty version of the thought experiment does achieve something, which is to avoid this problematic, question-begging sort of libertarianism. It doesn’t address the more difficult objection you’ve noted though.

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