The recursion theorem, by that name, is due to Kleene but owes its existence (and proof) to the work of Gödel (1931) on the incompleteness phenomenon. We look at few versions of this very powerful tool in what follows, and then come back to this comment regarding the connection with Gödel’s work. Theorem. (Kleene’s Recursion Theorem) If ImageszImages.f (z, Imagesn) images Images, then for some e, we have Images (Imagesn) ⋍ f (e, Imagesn), for all Imagesn.

Proof. Let Images. Then


Take e = (a, a).          □ ...

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