I didn't mean to suggest that quantum effects were the only source of uncertainty.
If I've got a cubic meter of pure water, I can slosh it around and observe all sorts of interesting effects. I can then model that cubic meter of water with another cubic meter. That second cube won't behave identically. A cubic meter of water has a very high Reynolds number and can have considerable chaotic turbulence (chaotic in the classical sense, not quantum). The exact motion of the water simply won't be the same, no matter how precisely you mimic the 'input' into the system (forced motion of the cube, for instance).
Nonetheless, the second cube is a fantastic way to understand the first cube, and in some way is qualitatively identical, even when the specific motions aren't replicated exactly. This is exactly the same for computational simulations of the fluid. Of course they can't predict chaotic behavior, but for all intents and purposes they can be just as useful as having that second cube of water.
Likewise, a computer simulation of a neuron may never exactly predict what a real neuron will do. Just like one neuron can never exactly predict what another neuron will do. Just like one bucket of water can never exactly mimic another. But who cares?
You're comparing two very different things here though. One bucket of water is substantially like another just as one brain is like another. A brain and a computer model of a brain are two very, very different things, with completely different meta-properties.
Yes, but what I'm pointing out is that what you are complaining computers fail to have, other physical systems also fail to have! Even a second bucket of water can't predict the first bucket of water! Thus, the fact that a computer can't either is sort of insubstantial to the question of a simulation's utility, no?
The essential point is that you can't model the behavior of a non-equilibrium system by modeling its constituent elements, which is what Kurzweil claims.
That no two non-equilibrium systems are exactly alike seems to me a different question.
If I've got a cubic meter of pure water, I can slosh it around and observe all sorts of interesting effects. I can then model that cubic meter of water with another cubic meter. That second cube won't behave identically. A cubic meter of water has a very high Reynolds number and can have considerable chaotic turbulence (chaotic in the classical sense, not quantum). The exact motion of the water simply won't be the same, no matter how precisely you mimic the 'input' into the system (forced motion of the cube, for instance).
Nonetheless, the second cube is a fantastic way to understand the first cube, and in some way is qualitatively identical, even when the specific motions aren't replicated exactly. This is exactly the same for computational simulations of the fluid. Of course they can't predict chaotic behavior, but for all intents and purposes they can be just as useful as having that second cube of water.
Likewise, a computer simulation of a neuron may never exactly predict what a real neuron will do. Just like one neuron can never exactly predict what another neuron will do. Just like one bucket of water can never exactly mimic another. But who cares?