Quine’s problem (which is different from the Duhem problem) begins by calling into question ‘the belief that each meaningful statement is equivalent to some logical construct upon terms which refer to immediate experience.’ (Quine, 39) However it was never Duhem’s intention to save the hypothesis, merely to indicate the element of uncertainty of falsifying evidence. Quine has taken the Duhem problem and extended it so that there is no limit to the set of hypotheses which face a test: “our statements about the external world face the tribunal of sense experience not individually but only as a corporate body.” (ibid, 41)
Of course, Quine is correct in saying that “Any statement can be held true come what may, if we make drastic enough adjustments elsewhere in the system. Even a statement very close to the periphery can be held true in the face of recalcitrant experience by pleading hallucination or by amending certain statements of the kind called logical laws. Conversely, by the same token, no statement is immune to revision,” (ibid, 43) but as Grünbaum shows, this is a trivial result.
It’s best not to reduce Grünbaum’s argument too far, but a brief analysis of the paper is necessary: Grünbaum demonstrates that while the Quine problem is trivially true as a matter of following the rules of logic, it leaves us only with no compelling reason to favor any of our auxiliary hypotheses over our scientific theories, and in its non-trivial form is a non sequitur. Anyone interested in examining Grünbaum’s argument fully can read the paper here [.pdf] (alt link).
In a letter dated June 1, 1962 and printed in Harding (1976), Quine responded to Grünbam. It’s interesting to understand Quine in light of this letter. I’ve reproduced it below, bolding specific passages of note.
Dear Professor Grünbaum:
I have read your paper on the falsifiability of theories with interest. Your claim that the Duhem-Quine thesis, as you call it, is untenable if taken non-trivially, strikes me as persuasive. Certainly it is carefully argued.
For my own part I would say that the thesis as I have used it is probably trivial. I haven’t advanced it as an interesting thesis as such. I bring it in only in the course of arguing against such notions as that the empirical content of sentences can in general be sorted out distributively, sentence by sentence, or that the understanding of a term can be segregated from collateral information regarding the object. For such purposes I am not concerned even to avoid the trivial extreme of sustaining a law by changing a meaning; for the cleavage between meaning and fact is part of what, in such contexts, I am questioning. Actually my holism is not as extreme as those brief vague paragraphs at the end of “Two dogmas of empiricism” are bound to sound. See sections 1-3 and 7-10 of Word and Object.
W. V. Quine
After all, if you see something that appears to be a black swan no matter how many tests are conducted, only by the most tortuous steps can one protect the theory “All swans are white.”