In set theory, a branch of mathematics, the condensation lemma is a result about sets in the constructible universe.

It states that if X is a transitive set and is an elementary submodel of some level of the constructible hierarchy L.

More can be said: If X is not transitive, then its transitive collapse in the Lévy hierarchy. Also, Devlin showed the assumption that X.

The lemma was formulated and proved by Kurt Gödel in his proof that the axiom of constructibility implies GCH.

Condensation Arguments

A condensation argument itself.

References

• (theorem II.5.2 and lemma II.5.10); condensation argument(s)

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