[whatshisface]

The brain is thought to be merely a computer in the original sense of a long strip of paper along with a scribe and a rulebook. The logic is, a Turing machine can simulate quantum electrodynamics to an arbitrary degree of accuracy. Then, two beliefs about physics and the structure of the brain are included:

1. There is nothing going on in the brain that would require simulation to infinite accuracy. Not even a chaotic system would have this property, because they take a finite time to "blow up" an initial uncertainty, and the smaller the initial uncertainty the longer they take to blow up. For this proposition to be violated there would have to be an undiscovered fininite-time nondeterministic blowup, which is unlikely, but I've heard rumblings that we haven't proven that it can't happen in Navier-Stokes. So maybe it can happen in the brain.

2. There is nothing going on in the brain that depends on nuclear physics or anything more "powerful" than quantum electrodynamics.

I have not seen any evidence that 1 or 2 aren't true for the brain, so that puts something behind saying it's "merely a computer."