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  The Value, if any, of Decidability

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by Yuri Gurevich
http://research.microsoft.com/~gurevich/Opera/114.ps
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Abstract:

Quisani: Hello. It's that time of the year again when we have a discussion, isn't it? Author: Come on in. It is a busy time but I am happy to see you. Q: I am afraid my mood is rather critical today. A: That is all right. Speak your mind. Q: It is about computability and decidability. It seems to me that logicians' computability has little to do with real computability. Some so-called computable functions are not computable in any practical sense. It is ridiculous to call them computable. A: It is well known that some computable functions are not feasibly computable. Q: But in what sense are they computable? You, logicians, have hijacked the notion of computability. Computability should mean practical computability. A: Practical computability is too hard to define. Take a function f, say, from binary strings to binary strings which is not computable by any Turing machine, and define g(x) =

Citations

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