 Why is there no Liar paradox in this sort of hierarchy of languages? Because the restriction that no truth predicate can apply to sentences of its own language is enforced as a syntactic one. Any sentence \(L\) equivalent to \(\neg \Tr(\left\ulcorner L\right\urcorner)\) is not syntactically well-formed. There is no Liar paradox because there is no Liar sentence. See the entries on  Tarski  and  Tarski’s truth definitions  for more on Tarski’s views of truth.