 Suppose now t is theoretical with respect to a theory T. Then it holds that in order to measure t, we need to assume the truth of some axiom \(\phi\) of T. Suppose, further, that t has occurrences in \(\phi\), as is standard in examples of T-theoreticity. From this it follows that, in standard truth-conditional semantics, the truth value of \(\phi\) is dependent on the semantic value of t. This leads to the following epistemological problem: on the one hand, we need to know the extension of t in order to find out whether \(\phi\) is true. On the other hand, it is simply impossible to determine the extension of t without using \(\phi\) or some other axiom of T. This mutual dependency between the semantic values of \(\phi\) and t makes it difficult, if not even impossible, to have evidence for \(\phi\) being true in any of its applications (cf. Andreas 2008).