Willard Van Orman Quine (1908-2000), the American mathematical logician, has claimed that when translating an alien language we construct hypotheses as to what is being said, or what items the words refer to; however, except in a few basic cases, it is impossible in principle to decide conclusively between different hypotheses which differ in ways affecting not only the meaning but even the truth of what is being said.
Quine’s example is that a ‘native’ might utter the word ‘gavagai’, which we take to mean ‘rabbit’; but it might be interpreted (with suitable adjustments to our interpretation of the rest of the sentence) as ‘undetached rabbit part’, or ‘momentary temporal part of an enduring rabbit’, and so on.
Strictly, this indeterminacy applies to all translation or interpretation, even within one language. This makes Quine doubt whether there really is such a thing as synonymy, and is connected with his holism.
Also see: principles of charity, humanity, radical interpretation
W V O Quine, Word and Object (1960), ch. 2