X-Message-Number: 11254
From: Thomas Donaldson <>
Subject: Finite versus finite-state machines. Why?
Date: Fri, 12 Feb 1999 00:13:28 +1100 (EST)

To Mike Perry again:

Yes, I know that finite is not the same as finite-state. That's exactly
why I provided those examples.

The real issue you raise is that of whether the Universe itself is
finite-state. It seems to me that if it expands indefinitely then that
idea looks shaky from the start --- and current cosmological results,
especially experimental results, suggest an indefinite expansion. 
Furthermore it's far from obvious that quantum theory (which will someday
be superseded by a broader theory containing both general relativity 
and quantum theory) means that everything is a finite-state machine.
Consider the spectral emissions from a single atom at a range of 
velocities from close to c to 0, coming and going. Now consider the
same for other kinds of atom, particle, etc. IF there is no common 
factor, then there will be an infinity of possible emissions --- in 
addition to the infinity of possible locations given by an indefinitely
expanding universe. (Planck's constant does not obviously mean that 
there is a common factor, if I understand quantum mechanics rightly).

Furthermore, suppose for the sake of argument that human beings are
(at least over a period of a few years) finite-state machines. If 
over time they show that they are finite but not finite-state, the
period of a few years really does not matter very much. 

And just what does this idea tell you about human beings (or anything
else)? If we had only TWO possible states, that would be significant.
Even if we had only 100 possible states, that would be significant. But
if we have 100 trillion possible states, the simple number of states
starts to change the issue entirely. Do you propose to understand 
people by listing all possible people states? (And naturally, since
the possible states will change with time, your list will become obsolete,
late or soon). If you believe that it means we can be copied by a 
finite-state machine, rather than simply a finite machine, just what
special difference does that make? 

To make my own view clear here, I will say that we can very likely be
copied by a "machine" (if we extend the definition broadly enough that
we ourselves are machines in the first place). It may need parts which
at present only biological methods produce, especially allowing growth
and some kinds of self-repair, but that does not in itself mean that
it cannot be thought of as a "machine". But it is exactly that insistence
on a FINITE-STATE machine which I do not fully understand.

And oh yes, I agree that we can work on both. I would hope that Saul Kent
or some other leader in 21st Century Medicine will soon provide us with
means to help out their research, much more than we can do now.

			Best and long long life to all,

				Thomas Donaldson

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