BonJour, again
I'm well over half way into BonJour's excellent book, and have read his rejoinders to objections to the tenability of a moderate rationalist epistemology. I won't concern myself much with these (but I believe he's done an excellent job of deflecting the various criticisms, many of which are ill-conceived, like the charge of "dogmatism"), and will note that unlike many modern philosophers (particularly of the neo-analytic tradition), BonJour takes the notion of concepts seriously. In so doing, he quotes an author who acts as though there's a clear divide between our "concepts" and the world of things and objects. BonJour, in characteristically good sense, poses the question "but why should we think of them this way" (my own words)? He notes we can all agree that the possession of a concept of a given thing X suggests at least that we can think of X's, classify things as X's and often recognize X's in appropriate circumstances. However, why should this lead us to think that concepts are in any way dichotomous with the notion of reality? He asks, if not reality, whence do our concepts ultimately derive? My concept of redness derives from my encountering things which instantiate the property; one may object that the claim that "nothing can be red and green all over, in the same respects", pertains solely to my concept of redness, but why should we think that it follows from this that what is represented in mind is merely some subjective entity and not an objective property of something? With no good answer to count in the favour of such a view, we have no reason to do so. I am glad that BonJour gives such serious consideration to the role of concepts, because many seem to merely gloss over it; yet it is vital for any epistemological viewpoint to take their role most seriously, lest one confuse how that role might be filled. BonJour is of course concerned with concepts and their interrelation with the world conceived of as a ding an sich, and given his criticism of Kant, I think he'd agree that the Kantian worldview (particularly the impositionist strain) is hard-pressed to give a good account of our concepts and their relation to reality without lapsing into subjectivism.
BonJour later, in a section focusing on metaphysical objections to rationalism, goes on to consider the nature of various objects of a priori cognition (e.g. numbers) and recounts some alternative ways of explicating concept-formation. Though he seems to favour a sort of Platonism, he gives positive consideration to the Aristotelian notion of forms being instantiated by various things in the real world, as well as concept empiricism (roughly similar, and closer to the Objectivist epistemology, where abstraction from concretes allows the formation of concepts), and claims that it at least can account for the causal role which abstract concepts figure in justifying various a priori claims. The book should thus be of interest to Aristotelians as well as other rationalists of the moderate sort, for its close examination of various oft-neglected areas of philosophy.