Full Idea
Axiom of Constructability: this is the statement V = L (i.e. ∀x ∃α(x ∈ L(α)). That is, the universe of well-founded von Neumann sets is the same as the universe of sets which are actually constructible. A possible axiom.
Gist of Idea
Constructibility: V = L (all sets are constructible)
Source
Kenneth Kunen (Set Theory [1980], §6.3)
Book Reference
Kunen,Kenneth: 'Set Theory: Introduction to Independence Proofs' [North-Holland 1980], p.170