Human mind Turing computable according to Eliezer

From: Eliezer Yudkowsky (
Date: Wed Oct 06 2004 - 16:35:08 MDT

Robin Lee Powell wrote:
> At we have:
> Penrose isn't trying to explain quantum physics; he's trying to
> persuade you that the human mind isn't Turing-computable.
> (Penrose is right about this, although purely by coincidence.)
> But at we
> have that human thought, at least, *is* turing computable.
> I'm not certain that this is a contradiciton, but I'd like to see
> more about Eliezer's views on this point; anybody got a link?

I was once a Penrosian noncomputationalist, for much the same reasons then
as my friend Mitchell Porter is now:

i.e., "Consciousness is so darned mysterious, and yet we already understand
the nature of computation very well, so if consciousness were computable we
would understand it already; plus the nature of computation seems
incompatible with the nature of consciousness; no matter how we manipulate
computing elements they'll never add up to quales."

I would be hard put to pinpoint the exact time when my opinion changed, but
my guess would be in the vicinity of late 2002. IIRC, that was when my
understanding of human cognition reached the point where I could start to
see that the answer didn't have the form I'd initially assumed. My
rationalist's postmortem (i.e., the rule I should have followed to have
never made the mistake in the first place) is that I saw a mysterious gap
in my knowledge, and I looked for a mysterious substance to fill the gap.
In retrospect, the blindingly obvious historical analogues include
"phlogiston" and "elan vital", the mysterious substances once postulated to
explain the mysterious phenomena of chemistry and biology. It seems to be
a flaw in human psychology; it's certainly a very common episode in the
history of science. "Emergence" as an explanation for intelligence is
another example of the same mistake.

I underestimated the power of the mundane. The problem with reading the
history of scientific revolutions, rather than living through the
experience, is that we don't assign the same weight to dry history as
living experience. It's just something we read about that happens to
strange people in books, much like Tolkien is an account of things that
happen to strange people in books.

Only now do I appreciate how reasonable the mistake of the vitalists must
have seemed *at the time*, how *surprising* and *embarassing* it was for
reality to come back and say: "Yep, *still* just mundane physics."

By "mundane", I mean here to say, same 'ol same 'ol physics; an explanation
that doesn't push the mystery into the level of organization dealt with by
physics; the explanatory burden, the unweaving of the mystery, carried out
on a higher level, rather than exporting the mystery into the low-level
elements. Perhaps the vitalists would also have protested, just as did my
earlier self, that to say 'consciousness involves quantum gravity' is not
going outside physics. But there is definitely a whiff about it of the
mysterious, the non-mundane, just like incorporating elan vital into
physics. And it pushes the explanatory burden into involvement with the
lowest level of then-known physics; this is almost always a mistake when
the impetus comes from a non-physics field. The only successful example I
can think of is Darwin versus Kelvin on the age of the sun. And even
there, the answer was just more of the same math; nothing *mysterious*.
And so I specify 'mundane physics'.

Mundane reductionism always, always, ALWAYS wins. If you think that is too
much emphasis, I should put in a few hundred repetitions of "always", one
for every historical case in which reductionism won.

In every generation it is the same plea: "No, this time it really *is* too
mysterious for science." The children grow up in a world where stars and
chemistry and life have always been mundane and previous generations were
just being silly mystics. And when they encounter something that's
*really* inexplicable, like consciousness, why, such a mystery has never
happened before, it is wholly unlike such non-mysterious things as stars
and life forms. Surely if there were a mundane explanation we would have
found it already. As if stars and life forms had not been great mysteries
for millennia on end, until one day someone solved them, and then they were
not mysteries any more.

I did not comprehend the power of the mundane explanation. It's a common
enough human problem. Now that I know what to look for, I see people doing
it all the time. Lesson after lesson after lesson of mere history, even if
the universe repeats the point a thousand times over, don't have the same
emotional force as a single personal experience.

But now I know better.

Eliezer S. Yudkowsky                
Research Fellow, Singularity Institute for Artificial Intelligence

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