Invisible wrote:
> Sure. But a UTM is carefully *designed* to be universal. Wolfram asserts 
> that many kinds of things "just happen to be" universal.

No, he asserts that many things just happen to be capable of being designed 
to be universal. A UTM is just the kind of TM that's universal. Rule 110 is 
only universal if you initialize it with the appropriate program in the 
cells to start with.

> demonstrates that just one of them is definitely Turing-complete.

It's turing complete only when running on the right program, initialized 
with the right set of data on the cells. 110 itself doesn't calculate 
anything except what rule 110 says to calculate.

>>> (Presumably such a result would include deciding exactly when a 
>>> simple system is or isn't Turing-complete.)
>>
>> We already have that too.
> 
> Really? So you can tell me exactly which CAs are or aren't 
> Turing-complete then?

Sure. The ones that can emulate arbitrary turing machines are turing 
complete. :-)  Oh, you mean, can I tell that just by looking without doing 
any mathematical proofs? No. :-)

> Yeah, even after reading NKS, I'm still not *exactly* sure what he was 
> getting at. Maybe he isn't either...

He's getting at "Hey! Hey, look at me! I should be famous!"

-- 
Darren New, San Diego CA, USA (PST)
   Forget "focus follows mouse." When do
   I get "focus follows gaze"?

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