On 20 Jul 2011, at 18:42, meekerdb wrote:

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On 7/20/2011 6:43 AM, Bruno Marchal wrote:I'm afraid this is not true. Some people even argue thatcomputationdoes not exist, the physical world only approximate them,according tothem. I have not yet seen a physical definition of computationHow about "a series of causally connected states which process information"Can you give me a physical definition of the terms "series","causal", "connected, "states", "process", and "information"?And I am very demanding: I would like an axiomatic definition.In absence of such a definition, you are just describing animplementation of a computation in what you assume, implicitly, tobe a natural universal system., except bynatural phenomenon emulating a mathematical computation. Computerandcomputations have been discovered by mathematicians, and there many equivalent definition of the concept, but only if we accept Church thesis.Now if you accept the idea that the propositions like "if xdivides 4then x divides 8", or "there is an infinity of twin primes" aretrueor false independently of you, then arithmetical truth makes*all* thepropositions about all computations true or false independently ofyou. The root of why it is so is GĂ¶del arithmetization of thesyntaxof arithmetic (or Principia). To be a piece of a computation is arithmetical, even if intensional (can depend on the *existence* of coding, but the coding is entirely arithmetical itself.In short, I can prove to you that there is computations inelementaryarithmetical truth, but you have to speculate on many things toclaimthat there are physical computations. Locally, typing on thiscomputer, makes me OK with the idea that the physical realityemulatescomputations, and that makes the white rabbit problems even more complex, but then we have not the choice, given the assumption.So I assumed I didn't understand Bruno's argument correctly.You seem to have a difficulty to see that elementary arithmetic"run"the UD, not in time and space, but in the arithmetical truth.He should. Truth is not existence.What is "existence"? If you refer to physics, then you are beggingthe question, or you are just assuming that we are not machine.BrunoBut I think you beg the question by demanding an axiomaticdefinition and rejecting ostensive ones.

Why?

`The point is that ostensive definition does not work for justifying an`

`ontology. That's what the dream argument shows. Being axiomatic does`

`not beg the question. You can be materialist and develop an axiomatic`

`of primitive matter. The whole point of an axiomatic approach consists`

`in being as neutral as possible on ontological commitment.`

Axiomatics are already in Platonia so of course that forcescomputation to be there.

`The computations are concrete relations. They don't need axioms to`

`exist. Then the numbers relation can be described by some axiomatic.`

`This means only that we *can* agree on simple (but very fertile) basic`

`number relations. For primitive matter, that does not exist, and that`

`is why people recourse to ostensive "definition". They knock the`

`table, and say "you will not tell me that this table does not exist".`

`The problem, for them, is that I can dream of people knocking tables.`

`So for the basic fundamental ontology, you just cannot use the`

`ostensive move (or you have to abandon the dream argument, classical`

`theory of knowledge, or comp). But this moves seems an ad hoc non-comp`

`move, if not a rather naive attitude.`

Bruno http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com. To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/everything-list?hl=en.