[nmaley]

Good point. The essence of processing is the transformation and combination of signs. Processing a sign is a kind of energy transformation. The process takes input signs, performs some kind of energy transformation, and produces a new sign, with different signification, which may be a better or more useful signifier for some purpose. Think NAND gates, or neurons. Example: if it looks like a duck and quacks like. duck, then it's probably a duck. A neuron summing 'looks like a duck' signal and 'quacks like a duck' signals is a more reliable signifier for ducks than either of the inputs. As for signs, see C S Peirce or Ruth Millikan for a clearer explanation. TLDR: Signs are relations between objects and processes (Sign, Signifier and Interpretant)

[TheOtherHobbes]

That's still begging the question - what is a sign (symbol/signifer)?

I'd suggest it's a signifier for a subjective state. You can persuade a symbol processor to do anything to any symbol collection, but the results are only useful if the symbols mean something - which is to say they have some analog to subjective experience.

If that's the case then computers and symbol processing are tools for working with subjective experience.

This does not mean there's a possible mapping between all symbol states and all of subjective experience. It's often assumed this is true, but it's a conjecture and has never been proven. It won't be proven until we know exactly what subjective experience is.

So the best we can say is that computers are tools for working with a subset of subjective experience.

Which is interesting enough in itself without being absolutist about it.