Can anything that can be said in one language be translated, without loss of meaning, into any other? Katz, inspired by Frege and others, argued for an affirmative answer to this question and proposed a Principle of Translatability. Since then, this alleged principle has come under scrutiny from linguists, who have proposed a number of counterexamples. While the consequences for Katz’s exact formulation of his principle are severe, the interpretation of the empirical data is often difficult and it is unclear whether slightly weaker principles may obtain. In my dissertation, I examine the literature discussing translatability and argue that it has suffered from a lack of precision regarding key terms, especially meaning and language. I propose that putting the question of translatability in terms of what Chomsky called I-languages allows better theoretical traction, although the exact question that we end up with looks very different from the one that we started with.