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Single Idea 10038

[filed under theme 5. Theory of Logic / K. Features of Logics / 8. Enumerability ]

Full Idea

In order to be sure that new expression can be translated into expressions not containing them, it is necessary to have a survey of all possible expressions, and this can be furnished only by syntactical considerations.

Gist of Idea

A logical system needs a syntactical survey of all possible expressions

Source

Kurt Gödel (Russell's Mathematical Logic [1944], p.448)

Book Ref

'Philosophy of Mathematics: readings (2nd)', ed/tr. Benacerraf/Putnam [CUP 1983], p.448


A Reaction

[compressed]


The 10 ideas with the same theme [whether all formulae in a system can be specified]:

There are infinite sets that are not enumerable [Cantor, by Smith,P]
A logical system needs a syntactical survey of all possible expressions [Gödel]
For a reasonable language, the set of valid wff's can always be enumerated [Enderton]
Effective enumeration might be proved but not specified, so it won't guarantee knowledge [Tharp]
A complete logic has an effective enumeration of the valid formulas [Tharp]
A set is 'enumerable' is all of its elements can result from a natural number function [Smith,P]
A set is 'effectively enumerable' if a computer could eventually list every member [Smith,P]
A finite set of finitely specifiable objects is always effectively enumerable (e.g. primes) [Smith,P]
The set of ordered pairs of natural numbers <i,j> is effectively enumerable [Smith,P]
The thorems of a nice arithmetic can be enumerated, but not the truths (so they're diffferent) [Smith,P]
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