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pdonis an hour ago

> any nontrivial axiomatic system has statements which are true but unprovable

Although this is a common way of stating what Godel's incompleteness theorem tells us, it's actually not correct. As was posted upthread, when you combine Godel's first incompleteness theorem with Godel's completeness theorem (all this in first-order logic), you find that, for any sentence that is not provable in a system of first-order logic (such as the Godel sentence for that system), there must be a semantic model of that first-order logic in which the sentence is false. (I gave an example of such a model for the first-order axioms of arithmetic upthread.)

kerwioru9238492 an hour ago | parent [-]

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