Rickert on embedded computation (was re: science of consciousness.)

Neil Rickert rickert at cs.niu.edu
Thu Apr 30 12:08:08 EST 1998


patrick at gryphon.psych.ox.ac.uk (Patrick Juola) writes:
>In article <6ia3l2$lea at ux.cs.niu.edu> rickert at cs.niu.edu (Neil Rickert) writes:
>>patrick at gryphon.psych.ox.ac.uk (Patrick Juola) writes:

>>>But Turing machines neither need nor are expected to predict their
>>>inputs.

>>Bah! Humbug.

>>Turing machines have no input.  The data is all there on the tape
>>before they begin execution.

>But it needn't be.  Because the Turing machine can't control its
>inputs, it might just as well all be on tape at the beginning.

Thank you.  You have made my point perfectly.

In other words, to model certain types of computational problem on a
TM, we must change the problem to fit the TM.  We must eliminate the
interactivity.  To model Win95 on a TM we must treat it as if the
complete set of mouse movements is already on the tape when we switch
on the computer.

Or, in other words, the TM only models a highly idealized version of
what happens in the actual computer.  And that is what I have been
arguing all along.

>That's the difference between a TM with input and a TM with an
>oracle.  An oracle-TM can phrase a question *and get an answer*.
>The inputs to a TM -- or to a real computer -- need have nothing
>to do with the current machine state.  Even when your Mac apparently
>locks up waiting for you to click the "confirm" button, what it's
>really doing is reading successive bits from the input tape waiting
>for one that it likes....

No.  What it is really doing is waiting for you to click the
"confirm" button.  It isn't really reading successive bits from any
input tape, for there is no input tape.  In terms of the cpu
activity, it is idling or executing a different task until an
interrupt signals the mouse action.

So, when you say "what it's really doing is reading successive bits
..." you mean that you have invented your own private reality, and
then described what happens in that purely invented reality.




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