If historical importance is judged by “extensiveness of influence”—what might be called the Citation Index standard—then the repetition of the “clichés Norris rises above” is more important than Norris. Watson names no one who repeats the clichés, however, because they are not important to the history of philosophy. And why? Philosophy is not just anything that is written on philosophical questions or in philosophical language, but the best (“best attack,” “best informed”) and most (“most careful,” “most extensive”).
Isn’t Norris’s historical importance precisely his greatness as a philosopher despite his contemporary neglect? If his excellence as a philosopher is compared to the extensiveness of his influence, wouldn’t Norris be correctly described as an underrated philosopher?
It isn't difficult, however, to name the people who repeat the clichés, precisely because they are all names that are, in fact, important to the history of philosophy: Hobbes, Locke, Hume, and so forth. The clichés had more extensive influence than the serious criticism. Thus a historian of philosophy is faced with two distinct kinds of importance, which can and sometimes do diverge: actual influence and comparative excellence. I would say that Norris is, in fact, an underrated philosopher, and I'm not quite so critical of evaluations like 'underrated' and 'overrated' as Miriam, but this sort of judgment is something that can only be made relative to particular features along one of these lines: Norris had some (minor) influence on others and/or came up with (some) reasonably good arguments.
Nor does philosophy simply consist in 'the best and the most'. If we allow ourselves a probably too-crude schematism, we can say that the historian of philosophy examines ideas, positions, and arguments in three aspects: they have their own structure, they are held for various reasons and under various motives, and they can be and are communicated to others. Each of these aspects can be dealt with in a more specific and a more general form. Structure we deal with by analysis (if we examine them on their own) or by placing them in their dialectical context (if we examine them in relation to other ideas, positions, and arguments); the motivations we examine individually (as in philosophical biography) and abstractly (by relying on a moral psychology of philosophy, which ideally would include the tools of a cognitive science of philosophy, but is more usually done in a more rule-of-thumb way); and the communication we look at in terms of the particulars of the case (which is history of philosophy at its most historical) and in terms of the principles governing the abstract relationships in the social networks (which is, effectively, sociology of philosophy). All of these are essential, and it is noteworthy that of the two kinds of importance, comparative excellence in kind has only to do with structure, whereas extent of influence has only to do with communication. And it actually doesn't matter much whether Norris is a great philosopher in either of these ways: what is important is that he does have some good arguments and that he did have some influence. British Malebrancheanism was an extraordinarily minor strand of philosophy; Norris's arguments against the agent intellect are of almost no historical significance, if by that we mean to indicate influence on other philosophers. They did not change the way people thought about the subject, because no one paid attention to them -- neither the major philosophers of the period nor the lingering remnants of early modern scholasticism. They fell between the cracks.
Thus if I call Norris an underrated philosopher, it's important to understand that there is no single standard of what counts as underrated. This does not mean that we can't evaluate anyone as underrated or overrated, but only that when we are doing so we can't assume that there is a single standard of importance governing the evaluation. Values are not the problem: rather, we need to be taking care that the limits of our evaluations are taken into account. The neglect of Norris makes complete sense when we look at his influence: he had some, but it was limited and did not last. It makes complete sense as well given the interests and projects of the time. Only when we take interest in quality of argument against (for example) scholastic views of intellect and reason do we see him stand out: in a field of rationalists and empiricists only a few rationalists bother to address the third major view of intellect and reason still in existence, and except for Norris these are not especially high-quality. There is a very straightforward way in which the clichés Norris rises above are more important than any of his interesting arguments: if you want to understand the historical course of philosophy, it is the clichés that matter, not the high-quality arguments. And in history of philosophy this is indeed a form of importance: one wants to understand the history, after all. And philosophy is not just 'the best and the most'; missteps and failures can be philosophical, too, and interesting to the historian of philosophy precisely because of their contrast with things that are more excellent.
So I agree entirely with Myers that we should not be squeamish about value terms; but I think it is still true that our evaluations will often be relative to a particular set of factors. Importance, whether considered in terms of quality or extent of influence or some mixture of both, will always be importance with respect to this or that point.