1Not able to be firmly established or refuted.
(of a proposition or theorem) not able to be proved or disproved.
- ‘Godel showed that in any formal system adequate for number theory there is an undecidable formula, that is, a formula such that neither it nor its negation can be proved.’
- ‘In Undecidable theories Tarski showed that group theory, lattices, abstract projective geometry, closure algebras and others mathematical systems are undecidable.’
- ‘Viruses are free to mutate into an infinite variety of functionally equivalent forms, whereas the process of establishing their equivalence is undecidable.’
- ‘And we know that 1st order logic is undecidable,’
- ‘All we could achieve by our mathematics would be non-constructive existence proofs that told us that they existed, in much the same manner that we can deduce the existence of undecidable propositions.’