In a recent I argued that one could derive a contradiction by combining three of Quine's philosophical theses, namely (i) his behaviourist inference (BI) from the indeterminacy thesis-that there is, beyond a certain point, no objective basis for choosing between various manuals of translation, (2) his mind-body theory (QMB) and (3) his restriction of the underdetermination of physics to an epistemological or inductive one (QRUP). My procedure, which I shall not recapitulate in detail here, was to picture two psychophysicists who use different manuals of translation, who apply QMB in their practice, and who seek to explain a particular piece of behaviour each by the theory he has developed. My claim was that under a certain possible development BI would be violated if QRUP also held. In a reply2 to my paper Mr. B. G. Crabb argues that my conclusion that Quine's theses are jointly inconsistent is not established. His reason (if I have understood him correctly) is as follows. My argument relies critically on supposing that our psychophysicists proceed to their explanations on the basis of translation; they must (in my Gedankenexperiment) have translated their subjects' utterances when they established their correlations, and they must now translate the words of the subject whose behaviour they are currently explaining. But, Crabb replies, why are they committed to this dependence on translation? Why should they not, ignoring what is said by their subject, proceed directly to a physiological explanation of the behaviour in question by the ordinary methods of physiology? Why therefore should a translational indeterminacy be regarded as coming into conflict with QRUP, since translation need not enter at all into what the psychophysicists do? The difficulty with this objection is that it interprets my argument as claiming that we cannot combine BI and QRUP without inconsistency. But I did not claim that, and can see no basis whatever for thinking that it is true. The inconsistency, I claim, arises when we combine QMB, BI and QRUP. QMB is a theory of mind which identifies mental states with certain physiological correlates thereof. (For sundry qualifications see my earlier paper.) It prescribes a certain routine for determining such correlates. Now what of psychological explanation? The surrogate of psychological explanation must, on QMB, consist in adducing as explanatory of behaviour the physiological state correlative to the mental state which we would normally invoke to explain that behaviour. Thus, in my story, the two psychophysicists are applying QMB, each according to his lights, when they give their diverse explanations of the fact that