There is no rational basis for assuming it is not, as we have not a single example of a computable function outside the Turing computable set.
The term "computer" has it's original outside of "electronic computer". It used to be a role, a job function. There has been no time in human history where the only computers have been electronic computers.
But, sure, let's be more precise: Any Turing complete system is equivalent to any Turing complete computer and can reasonably be called a computer, but let's also limit it to any system that can not compute functions outside the Turing computable set. We don't know of any such systems that have been shown to compute functions outside the Turing computable set, at all, including brains.
The rational basis for assuming the brain is a computer is that we have not a single shred of evidence that exceeding Turing computability is possible, nor any theory for how to even express a function that is computable for humans but not Turing computable.
If you can find one single such example, there'd be a rational basis for saying the brain isn't a computer. As it stands now, assuming it isn't, is nothing more than blind faith.
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The term "computer" has it's original outside of "electronic computer". It used to be a role, a job function. There has been no time in human history where the only computers have been electronic computers.
But, sure, let's be more precise: Any Turing complete system is equivalent to any Turing complete computer and can reasonably be called a computer, but let's also limit it to any system that can not compute functions outside the Turing computable set. We don't know of any such systems that have been shown to compute functions outside the Turing computable set, at all, including brains.
The rational basis for assuming the brain is a computer is that we have not a single shred of evidence that exceeding Turing computability is possible, nor any theory for how to even express a function that is computable for humans but not Turing computable.
If you can find one single such example, there'd be a rational basis for saying the brain isn't a computer. As it stands now, assuming it isn't, is nothing more than blind faith. .