X-Message-Number: 25097
Date: Thu, 18 Nov 2004 17:02:42 -0800
Subject: Computers and Brains (to Francois)
From: <>

Dear Francois:

You wrote:

"You have many times stated that a computer program behaving like a 
human mind would need to 'run' on some sort of hardware very much 
like a living brain, because a brain is not like a computer. It can 
grow new connexions and cull away old ones, reshaping its 
'circuitry' as it goes. That is very true. However, I think that 
the whole thing could be programmed in pure software, changing 
connexions and all."

The point is, when you program this in software, it is nothing more 
than a string of bits being manipulated according to rules. A 
string of bits isn't conscious---it can't be. For one reason, 
there's no objective meaning to a string of bits. Is it a brain 
program, or a stock advisor program for an alien civilization? It 
could be either or none of the above. Programs don't have an 
objective existence like physical things do. A CPU can't be 
anything but what it is, since it's a physical thing. There's no 
component of subjectivity involved.

Thomas has argued much the same, but in different words. Sure, he 
says, you might be able to upload (though I disagree with him 
here), but you would need hardware that replicates (to some extent) 
the human brain. A mere program running on a standard CPU wouldn't 

I should also point out that if quantum mechanics is at all 
relevant to who we are, how we experience things, or how we work, 
then a brain program is impossible, even in principle (the brain 
would not be Turing-computable). So not only would the brain 
program not be conscious, because its interpretation is subjective, 
but you couldn't even write it to begin with. So you would have to 
build a custom piece of hardware similar to (at least in some 
respects) the brain.

Best Regards,

Richard B. R.

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