	There is a formula of set theory that expresses the idea that X=L. It has only free variables for X and α. Using this we can expand the definition of each constructible set. If s∈L, then s = {y|y∈L and Φ(y,z...,z) holds in (L,∈)} for some formula Φ and some z...,z in L. This is equivalent to saying that: for all y, y∈s if and only if [there exists X such that X=L and y∈X and Ψ(X,y,z...,z)] where Ψ(X...) is the result of restricting each quantifier in