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Determinism vs. Free Will

What does it mean for our traditional conceptions of free will and moral responsibility that all our thoughts and all our behavior are caused by physical processes in the brain?

There is a long-standing philosophical debate (see Free will.) Determinism is a fairly clearly defined term, whereas Free will is not. In Freedom Evolves, Daniel Dennett finds considerable philosophical recreation in considering different sorts of free will and whether they are “worth having.” Our position is that because Prediction is Intractable, the threat to any sort of free will is overblown.

We can define determinism in two similar ways:

  1. If we could somehow rewind the world and replay it, exactly the same things would happen the second time around, or
  2. If we could exactly measure the entire state of the world and had the right physics, then we could predict what will happen next.

Right away we see that determinism also has a rather philosophical character, since neither of these things could ever actually be done. The first requires time travel, and the second requires a privileged observer outside the universe (as well as some really impressive measurement technology.)

Physical Nondeterminism

For the concept of determinism to have any practical relevance we must limit the discussion to small parts of the universe that can be isolated in a controlled environment so that they can be subjected repeatedly to the same stimulus. If we look at Atomic physics (likely the smallest scale relevant in brain function), then we find that atoms are in many ways highly deterministic. Each atom seems to be utterly interchangeable with other atoms of the same isotope, and properties such as excitation energy are so invariant that they are now used to define fundamental measurement units such as the second. However, if we look at phenomena such as the timing of Spontaneous emission, we find only randomness, and Quantum mechanics tells us that this non-determinism is fundamental.

So then we're done, right? No determinism, so having a physical brain does not constrain free will. Hold on… First of all, as Dennett points out, randomness is not a “form of free will worth having.” Second, as discussed in Mind, the brain is designed to overcome the fuzzy imprecise behavior of the goop it is made out of, keeping our hearts beating at an appropriate rate in spite of atomic scale randomness such as Brownian motion. Even so, since the brain is basically an Analog computer there is surely some level of true random nondeterminism that leaks into our decisions.

But even without this, human decisions would still be highly unpredictable due to the sheer complexity of the brain and the unpredictable inputs that each person constantly receives from the larger environment (which includes other unpredictable people reacting to our own behavior, adding to the Physical Chaos.)

Behavioral Regularities

In spite of underlying randomness and irreducible complexity, in our common experience we do see that people are somewhat predictable, showing a Personality or temperament that is reasonably consistent over time, as well as habits or other characteristic behaviors.

This differs from the sort of precise “I know what you will do next” determinism of philosophy thought experiments because it is only true in a statistical sense: “Joe tends to go and work out at the gym when he's had a bad day at work.” This sort of human predictability is real, and can at times seem like a sort of suffocating mechanical control that defeats our free will, especially when we are consciously trying to change how we behave. Though this sort of human determinism may be frustrating, it is familiar and unthreatening.

See Reprogramming the Mind.

New Developments

What is new is that fMRI and other improved measurement techniques are revealing more of the physical workings of the brain, undermining our naive dualism and suggesting the possibility that human behavior could be predicted much more accurately using these new means. Indeed, in the lab it has been found possible to predict simple decisions some seconds ahead of the apparent time of conscious decision.

Due to the fundamental intractability of complex systems, predictions of individual behavior will always be short-term, statistical, or both (as are weather predictions, and for the same reason.) However, improved instrumentation and analysis may allow more accurate and less subjective predictions of behavior. The most dramatic area of practical application of behavior prediction is in the control of socially unacceptable behavior, especially in the legal system. See The Law and Neuroscience Project and Neuroethics. There is also considerable interest in exploiting regularities in human behavior for financial and political gain (marketing, spin control.)

Since free will is traditionally understood as being a conscious process, see also Consciousness.


George Ortega, 2012/07/23 12:10

“Even so, since the brain is basically an Analog computer there is surely some level of true random nondeterminism that leaks into our decisions.

The problem for free will is that both determinism and randomness make it impossible, and there's no third option.

I did an episode of my show on this. Episode 14. Why Both Causality and Randomness Make Free Will Impossible. The transcript is available here

Robert MacLachlan, 2013/01/21 20:36

I agree that free will doesn't operate the way it has been supposed, either from the commonsense view (which is driven by an intuitive but non-physical Mind/Body Dualism), or in the philosophic view, which assigns far too much importance to the conscious mind (see Unconscious). What do we gain by saying that free will is an illusion? We still have to decide what to eat for breakfast, don't we? My preference is retread existing intuitive concepts of mind with a layer of physical realism, rather than saying free will is an illusion, consciousness is an illusion, the self is an illusion, morality is an illusion, etc. Of course! We don't perceive anything directly, as it truly is. Every time we open our eyes and see something, that's a creative act. Every time we speak, we're making up a Story.

In your transcript you present several arguments. One is that most of the action in the mind is in the unconscious. That's true. But then you say that “You don't have any control of your unconscious, so free will is unreal.” I don't agree. You are your unconscious. Nobody else is controlling your unconscious, and it isn't random either.

I think you are correct in rejecting quantum physics as a physical basis for the traditional philosophic free will (the uncaused cause), but you are far too uncritical in accepting intuitive notions of causality. The chain of causation is neither as direct or as weighty as you suppose. Events certainly have preconditions, but to say that everything has a cause is more an act of faith. Causality is one of those things that does have some basis in reality, but that we don't perceive directly. Humans have innate tendencies to perceive causal sequences (see Descarte's Baby) because this is useful and socially relevant information, but that doesn't mean we always get it right.

Malcolm Watts, 2016/04/12 21:35

“Events certainly have preconditions, but to say that everything has a cause is more an act of faith.”

   Is it? Anything that happens without cause can be classified as a miracle. Which of the two requires faith, miracles or cause and effect?  
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analysis/philosophy/determinism_vs_free_will.txt · Last modified: 2013/10/12 14:11 by ram