 A straightforward realist reply is that knowledge of the meanings of sentences with undetectable truth-conditions is acquired in the same way as knowledge of the meanings of sentences with recognisable truth-conditions: namely, compositionally by acquiring knowledge of the lexicon and the relevant compositional principles [Pagin  2009].[2]  Anti-realists respond by contesting the interpretation of the compositional principles that generate sentences with undetectable truth-conditions — where realists assert \(S \lor \neg S\) is true (\(S\) being the Socrates sentence), anti-realists maintain there is no ground for asserting this disjunction [e.g. Tennant 1987].