10.1.2. Reflexive prediction, determinism, and the impossibility of free will

 6th in free-will series

Will you—or won’t you—take an M & M candy in the next minute after it’s placed in front of you? In this thought experiment, we assume that I’m able to predict your action with absolute accuracy based on physics. I inform you that I predict you’ll take the candy, but you’re a rebellious sort, and just to prove you’re no automaton, you decide on defiance. Your proneness to disconfirm predictions deliberately seems to render impossible any prediction of your choice, provided you’re informed of it in advance. But remember I can predict your choice. 

    At least one of the following assumptions concerning the physical possibilities must be false to remove the contradiction:

    1. That it’s physically possible that you be informed of a deterministic prediction when you’re indifferent to the alternatives

  

    2. That it’s physically possible to predict your behavior precisely

  

    3. That it’s physically possible for you to defy the prediction

A.   Because you don't want to defy it

B.   Because you won't be able to defy it despite wanting to

The possibility of conveying a precise prediction (No. 1)

It might be claimed that physics precludes that you could ever be informed of a determinate prediction when you’re indifferent to the alternatives, since you’ll be moved to falsify it. But if perfect prediction is possible, conveying its substance should be easy: no barriers are apparent.

The possibility of predicting precisely (No. 2)

We may try denying the second assumption, that precise prediction of your behavior is possible. It might be said that human organisms aren’t the kind of systems that can be predicted precisely. But again, one must wonder why not. Organisms are but clumps of matter; they can be described as systems in biological terms, but otherwise they are no less subject to purely physical description than other purely physical systems. No specific barrier limits prediction of biological systems when they’re conceived as physical systems.

The possibility of defying the prediction: You won’t want to defy it (No. 3A)

The possibility of defying the prediction must be questioned. Perhaps you won’t choose to be negative, your character and personality notwithstanding. But the truth of the prediction doesn’t affect any of the things that we use to attribute a reactant tendency to infer what you want to do; its truth affords no cause for bringing other motives into play. A true prediction confronts you no differently from a false prediction: whether the prediction happens to be true or false has in itself no bearing on how it’s received.

The possibility of defying the prediction: You can’t defy the prediction despite wanting to (No. 3B)

Having excluded the other possibilities, we should conclude that you will confirm the prediction despite not wanting to confirm it. This result is due to your taking of the candy being a physical act, which must conform to physical prediction, whereas having an attitude of wanting is identified by psychological criteria and does not necessarily conform to any specific physical criteria.

A note on quantum indeterminacy

Although the ground is well traveled by others, I should say a couple of words about quantum mechanics in its bearing on whether absolutely true predictions really are physically possible. First, the relevant macroscopic states are essentially deterministic.  Second, quantum uncertainty doesn’t explain why in the thought experiment you would want determinately according to your character, for which expectation I argue.

Conclusion

The thought experiment serves as an “intuition pump” (Daniel Dennett) concerning the incongruence between mentalistic and physical concepts. Compatibilism is the doctrine that the world can be deterministic despite your ability to exercise “volition.” Compatibilism thus implies that in describing our “wants” we describe a real cause of our behavior.

Mental concepts, such as "wanting," refer only fictitiously. They serve fallibly to enhance foresight about our behavior and that of other people. Fatally for compatibilism, the thought experiment accentuates that fallibility.

10.1.1. Another refutation of compatibilism: Newcomb’s paradox shows that free will is entirely illusory

 5th in free-will series.

Hard determinists (such as I)—maintaining that genuine free will is illusory—typically concede that genuine volition exists but claim the sense of free will concerns thoroughgoing agent autonomy: origination. (See T. Honderich, A theory of determinism (1998).) Previous essays defended hard determinism by reducing origination to the illusory sense of free will, consisting of the misperception that experienced deciding causes action. In this essay, I attack the illusion of free will at its home base: volition. It is not even the case, I contend, that our behavior is under voluntary control.

Newcomb’s paradox is incoherent

My starting point is the well-known problem in philosophical decision theory called Newcomb’s Paradox. I don’t claim to be a serious student of decision theory; my purpose is to turn the paradox to a different purpose—different but not entirely novel. Others have argued that the denial of free will is inherent in the paradox’s assumptions, but I take the argument a step further by contending that in relevant part the assumptions are true.

In the form I’ll use, Newcomb’s Paradox concerns a game organized by a faultless Predictor. The game’s set-up consists of two boxes, one transparent and the other opaque. Predictor places a thousand dollars in the transparent box but places an amount in the opaque box that’s contingent on the prediction. Chooser is to pick either the opaque box or both boxes. When Predictor knows Chooser will pick the opaque box, it places a million dollars in it, but if Predictor knows Chooser will pick both boxes, it leaves the opaque box empty. Chooser’s best outcome would be to pick both boxes when it contains a million dollars, but the infallible Predictor then will have left the opaque box empty, since being infallible, it has predicted the choice. But the Predictor goes exclusively with its prediction and makes no changes after Chooser's actual choice, and following this line of thinking, Chooser should pick both boxes. If Predictor put the million in the opaque box, then Chooser gets $1,000,000 + $1,000 = $1,001,000. But since Predictor is always right, it would have predicted that Chooser would choose both boxes, so Chooser is stuck with only a thousand.

Both sides have advocates because valid principles seem to support either decision. Supporting the both-box choice is the principle that we should choose based on the consequences of our choices, that is, based on what they cause. The maxim holding that correlation isn’t necessarily causation expresses this principle. We should choose both boxes because what's done is done. The other principle is that we can rely on lawful regularities when they—as opposed to relations of mere correlation—underpin our choice. Since the Predictor always rewards the choice of the opaque box with $1,000,000 and punishes the choice of both boxes by awarding only $1,000, we should choose the opaque box. The two valid principles lead to contradictory solutions because the puzzle itself contains contradictory assumptions: if you can choose something besides what the Predictor prophesies, the Predictor isn’t infallible, since Predictor then can be wrong. If you focus on the assumption that Predictor is infallible, you pick the opaque box. If you focus on the causal consequences of your ability to choose, you choose both boxes.

Re-evaluating volition

Commentators haven’t widely recognized the incoherence of Newcomb’s paradox because (as tacit compatibilists) they don’t see how a precise prediction derived without considering Chooser’s volition could be perfect: why can’t Chooser contravene a determinate prediction in willful pursuit of its self-interest? The problem is evident if Predictor were to announce beforehand that it predicts Chooser will pick the opaque box: what’s to stop Chooser from refuting Predictor by picking both boxes—netting a $1,000 increase in payoff? Predictor’s infallibility might be said to stop Chooser, but the question is how could Predictor be infallible (or how could the universe be suitably deterministic) when Chooser may want to thwart the prediction, if informed. What’s the outcome when Chooser—as seems entirely possible—wants to pick contrary to prediction? The answer must be that Chooser fails to pick what it wants. If Predictor forecasts the opaque box and Chooser wills the both-box choice, Chooser can’t act according to its will. It will have to act as if in a hypnotic trance when hypnotic suggestion conflicts with volition. (Post-hypnotic suggestion may be a useful model for hard determinism.) 

The weakness of this solution to Newcomb’s paradox is abruptness. Why should choice suddenly become impossible when prediction is complete yet occur when prediction is almost complete? The paradox should force us to reconsider the general proposition that genuine volition exists, and Libet’s findings provide a basis for re-evaluation. If we will our behavior, how do we know we do, given that we find out that we carried out a willful act only after our brains transmit the effective impulse? I’ve been calling that impulse the “decision,” but Chooser frames the decision after the act. Our predecision intentions comport with our actions only because of the formers' abstractness and vagueness, and strict volition is an illusion caused by our flawed perception of mental temporality. The conclusion holding that perfect-prediction’s logical possibility precludes choice is a dispositive claim against compatibilism, which—to deny any contradiction between free will and determinism—analyzes free will as volition. Our acts aren’t truly voluntary. 

Changed on July 2, 2012, 11 a.m.: Clarified that Predictor announces prediction in second-to-last paragraph. (See discussion with Joseph.)

I elaborate on the logic of the second-to-last paragraph in 10.1.2 Reflexive prediction, determinism, and the impossibility of free will