Full Idea
The substitutional interpretation says the universal quantifier is true just in case it remains true for all substitutions of terms of the same type as that of the universally bound variable.
Gist of Idea
Substitutional universal quantification retains truth for substitution of terms of the same type
Source
Dale Jacquette (Intro to III: Quantifiers [2002], p.143)
Book Reference
'Philosophy of Logic: an anthology', ed/tr. Jacquette,Dale [Blackwell 2002], p.143
A Reaction
This doesn't seem to tell us how it gets started with being true.