Tarski's (T) schema says that:
- X is true if, and only if, p
- The first sentence that Janet uttered today is true if, and only if, snow is white.
Were the (T) schema Tarski's definition of truth, this could be the start of a criticism. For we do expect instances of definitional sentences to be necessary truth. E.g.,
- Patrick's best friend is a bachelor if, and only if, Patrick's best friend is a never-married, marriageable man
- F(X) if, and only if, G(X)