2019-02-08

I reviewed the “two flavors” of incompleteness theorems and the easy incompleteness proofs in Peter Smith’s book (chapters 6 and 7).

I started thinking about undecidability in logic, and wrote the page for the Entscheidungsproblem. I made some embarrassing realizations, like finally understanding that all the common undecidability statements (for first-order logic) are equivalent, and also realizing that undecidability for a logic is different from undecidability for a theory. It seems totally insane to me that this isn’t emphasized in the resources I have been consulting.

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