Quine's naturalistic holism is marked by the idea that our methodology should be concerned with empirical data as understood by modern science in conjunction with the idea that every theory is underdetermined by the data it espouses to interpret.
This seems to lead to the conclusion that our theories are never certain, and are always open to revision.
But suppose the traditional epistemologist thinks that what Quine means in the first half of this supposition, regarding his empiricism, is in need of clarification. The epistemologist would want to ask Quine just what qualifies as 'science' or more plainly 'empirical'.
Or perhaps in questioning Quine's holism the traditional epistemologist wants to know why Quine thinks to begin with that a theory being undertetermined by empirical data is suggestive of what Quine thinks it's suggestive of.
Furthermore, one might question the globalism of Quine's holism, and how he moves from points of an empirical nature to knowledge simpliciter.
These questions might very well arise in the spirit of Quine's holism itself, wherein their answers are uncertain and dictated by whatever conditions characterize their place in the 'web of belief', in which case Quine could respond to them with relative ease.
But where they are truly interesting is where they arise outside of the context of Quine's holism, in question of Quine's holism. The traditional epistemologist holds that unless these questions have specific answers there is no justification of Quine's holism, no reason for them to accept Quine's holism (and no reason for Quine to accept his own holism).
Indeed, when these questions are asked in the context of accepting Quine's holism as true, an inevitable circularity ensues, as Quine himself admits of his naturalism elsewhere.
For Quine's relativistic holism requires that there be no set 'criterion' for determining what is and isn't 'science', nor even a set criterion for what is and isn't 'holism'.
To accept Quine's holism is expected by Quine to be a provision that stems from his holism itself. But be it that accepting his holism is what is in question, it seems that Quine is begging the question against those who are seeking a standard or justification of his methodology.