equivalence thesis
The equivalence thesis states that for any proposed notion of truth, each instance of the schema "S is true if and only if P" resulting from the substitution of a translation of the sentence designated by S for P, is true. This thesis is often taken to be a minimal requirement on any notion of truth.

Note that the equivalence thesis does not presuppose a correspondence notion of truth. For example, deflationary notions of truth, such as the Quinian 'disquotational' notion, satisfy the equivalence thesis.
Whit Schonbein