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> The brain is mostly deterministic. Quantum-level nondeterminism has very low probability to matter much.

Sources, please?

At an atomic level, events are not deterministic.

At a molecular level, events are not deterministic.

Perhaps you are referring to parts of the brain that are not made of atoms?

Personally, I suspect that the brain is entirely non-deterministic in terms of the material it is made of and fine-grained behaviour [because physics and chemistry support that idea].

But I suspect the brain's structure does something to offset this at the larger scale, and make it more predictable/deterministic (averaging, wisdom of crowds, etc). However, I do not assert the latter as fact, merely my own speculation.

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At an atomic level, events are not deterministic.

At a molecular level, events are not deterministic.

Therefore, we all behave randomly. Qed.

It's controversial at best that atomic-level physics is non-deterministic.

http://scienceblogs.com/interactions/2007/06/08/on-quantum-m...

"The probabilities are what they are, no matter what we want, no matter what we visualize, no matter what we meditate upon while imbibing inspirational substances. It doesn’t matter how much you want that electron to be spin up, it doesn’t matter how many good “vibes” you give the electron about being spin up, it always has exactly a 1/2 chance of being spin up, a 1/2 chance of being spin down."

Sigh. http://lesswrong.com/lw/r5/the_quantum_physics_sequence/

Even if the evolution rule is deterministic, it's still epistemically/indexically nondeterministic from the perspective of the observer.

Quantum events in the brain would decohere almost immediately, leading to effectively nondeterministic behavior at any scale above the cellular. The philosophical determinism of wavefunction realism (which is the LW argument) is irrelevant to the actual behavior.

> At an atomic level, events are not deterministic. > At a molecular level, events are not deterministic. > Therefore, we all behave randomly. Qed.

This doesn't follow. The combination of many random events can be highly predictable.

Tossing a fair coin is random. Combining 10000 coin tosses will give you a result close to 5000 heads and 5000 tails, and I can predict you won't get 4000 heads and 6000 tails or 100 heads and 9900 tails.

So there's various types of randomness, and the more you average out uncorrelated events the more you get something very close to a predictable result.

Example via A. Einstein:

http://userpages.umbc.edu/~dfrey1/ench630/ein_ran_walk.pdf

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