Peter Jones writes:

> > I'm not necessarily talking about every possible computation being 
> > implemented by
> > every physical system, just (at least) the subset of finite computations 
> > implemented by
> > a physical computer or brain. I think this is another way of saying that a 
> > recording, or
> > a single trace of a computation branching in the multiverse, can be 
> > conscious. To prevent
> > a recording being consious yoiu can insist on counterfactual behaviour, but 
> > that seems an
> > ad hoc requirement introduced simply to prevent the "trivial" case of a 
> > recording or any
> > physical system implementing a computation.
> The requirement that computations require counterfactuals isn't
> ad hoc, it comes from the observation that computer programmes
> include if-then statements.
> The idea that everyting is conscious unless there is a good
> reason it isn't -- *that* is ad hoc!

No, it follows from the idea that anything can be a computation. I think this 
is trivially obvious, 
like saying any string of apparently random characters is a translation of any 
English sentence 
of similar or shorter length, and if you have the correct dictionary, you can 
find out what that 
English sentence is. This is analogous to finding an alien computer which, when 
power is applied, 
is set into motion like an inscrutable Rube Goldberg machine. If you get your 
hands on the 
computer manual, you might be able to decipher the machine's activity as 
calculating pi. Moreover, 
you might be able to reach inside and shift a few gears or discharge a few 
capacitors and make it 
calculate e instead, utilising the fact that the laws of physics determine that 
if the inputs change, 
the outputs will change (which, I trust you will agree, is the actual physical 
basis of the if-then 

Now, in human languages as in machine design, there are certain regularities to 
make things 
easier for user. It might be possible, albeit difficult, to decipher a foreign 
language or figure out 
what an alien computer is computing by looking for these regularities. However, 
it is not necessary 
that there be any pattern at all: the characters in the unknown language may 
change in meaning 
every time they appear in the string in accordance with a random number 
generator, a cryptographic 
method called a "one-time pad". Similarly, the meaning of the physical states 
of the alien computer 
could change with each clock cycle according to some random number sequence, so 
that if you had 
the key you could figure out that the computer was calculating pi, but if you 
did not its activity would 
seem random. I don't think it would be reasonable to say that the computer is 
only calculating pi when 
you have the manual at hand ready to refer to, even though without the manual 
the computer is 
completely useless to you if you want to calculate the area of a circle, for 

Remember, even the apparently random computer handles counterfactuals, in that 
if a gear or a 
semiconductor junction were changed, the whole subsequent activity of the 
machine would change, 
and the manual would tell you how the computation had changed.

You could dismiss the computations of random physical systems as trivial or 
useless, but what if you 
believe that some computations can be conscious? It would be no easier for us 
to observe or interact 
with these computations than it would be for us to observe or use the pi 
calculation, but by 
definition the conscious computations *themselves* would be self-aware.

We might say in the above cases that the burden of the computation shifts from 
the physical activity 
of the computer to the information in the manual. The significance of this is 
that the manual is static, 
and need not even be instantiated if we don't care about interacting with the 
computer: it is a 
mathematical object residing in Platonia. 

Stathis Papaioannou
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