The article explores the connections between the recursive predicates of provability (Pf) and refutability (Rf) in formal logic.
It begins by defining the Rf predicate as a recursive predicate that encodes the notion of refutability, similar to how the Pf predicate encodes provability. The author then establishes a series of lemmas that clarify the relationships between these two predicates.
Lemma 1 shows that for any formula α, it is not possible for both Rf(n, ⌜α⌝) and Pf(n, ⌜α⌝) to hold, where n is a natural number. Lemmas 2 and 3 provide further insights into the characteristic functions of Pf and Rf, demonstrating their complementary nature. Lemma 4 then consolidates these findings, establishing that for any formula α, either Pf(n, ⌜α⌝) or Rf(n, ⌜α⌝) holds, but not both.
The article then discusses the implications of these results for the notions of provability and refutability, and their connections to the concept of undecidability. It argues that the recursive definition of Rf, alongside the lemmas, helps to shed light on the nature of indeterminacy in formal systems, suggesting that it may not be as inherent as previously thought.
The author concludes by highlighting how the insights gained from the investigation of the Pf and Rf predicates can provide new perspectives on Gödel's incompleteness argument and the underlying notions of codings and self-referentiality.
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by Paola Cattab... klokken arxiv.org 04-08-2024
https://arxiv.org/pdf/2404.04038.pdfDypere Spørsmål