Self-Satisfaction
It seems reasonable to assert "a theory of truth is itself true if and only if it fulfills its own criteria for truth" (I'll call this the "self-satisfaction principle"). If I say "x is true if God said so", this fulfills the self-satisfaction principle. However, if I say "x is true if and only if God said so", this does not (precisely because I made the claim, and God has not).
Traditional theories of truth don't fare well:
- Correspondence: the theory is an abstraction and cannot possibly correspond to anything concrete
- Coherence: the theory initially stands alone, and has nothing to cohere to
- Pragmatism: is it pragmatic to be a pragmatist? Outside of an initial assumption of order and uniformity, coupled with a utility function, no.
Unfortunately, creating "only if" theories of truth that fulfill the self-satisfaction principle is pretty easy (if I say, "x is true only if I say so", if I write "x is true only if I write it"). A real theory of truth would have to fulfill the self-satisfaction principle and describe an "if and only if" relationship.