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Impossibility Theorem

Logic, Foundations and Set Theory

An impossibility theorem is a theorem that demonstrates a problem or general set of problems cannot be solved; such results are also known as proofs of impossibility, negative proofs or negative results. The cited article says they often resolve decades or centuries of work spent looking for a solution by proving there is no solution, that proving something is impossible is usually much harder than the opposite task because a proof must work in general rather than for one example, and that they are usually expressible as negative existential or universal propositions in logic. The irrationality of the square root of 2 is named as one of the oldest such proofs. Theorems that rule out a construction or solution are grouped under this concept.

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Source Impossibility Theorem

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Source Vaught Conjecture (Wikipedia)
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Impossibility Theorem
  • Wikipedia, lead section
    In mathematics, an impossibility theorem is a theorem that demonstrates a problem or general set of problems cannot be solved.
  • In Branch: Logic and Foundations, Lead section
    In mathematics, an impossibility theorem is a theorem that demonstrates a problem or general set of problems cannot be solved. These are also known as proofs of impossibility
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Vaught Conjecture (Wikipedia)
Statement Form Of: Vaught's Theorem, Section: Vaught's theorem
Quote, Statement Form Of: Vaught's Theorem, Section: Vaught's theorem
Vaught proved that the number of countable models of a complete theory cannot be 2.
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