 \(T\), the Truth, is a theory only in the technical Tarskian sense, not in the ordinary everyday sense of that term. It is a set of sentences closed under the consequence relation: \(T\) may not be finitely axiomatizable, or even axiomatizable at all. However, it is a perfectly good set of sentences all the same. In general, we will follow the Tarski-Popper usage here and call any set of sentences closed under consequence a theory, and we will assume that each proposition we deal with is identified with a theory in this sense. (Note that theory \(A\) logically entails theory \(B\) just in case \(B\) is a subset of \(A\).)