I was reading through some old Peirce-L posts and came upon some stuff on Duns Scotus some might find interesting. Scotus is an important influence on Peirce. Although one suspects many things Peirce arrived at he arrived at on his own and the parallels are merely interesting happenstance. I'd also note that one probably ought notice some parallels to European neo-phenomenology. (What I've taken to calling Heidegger and those of his ilk.) This is from Scott David Foutz writing in Quadlibet 6:4.
Scotus' position, which has come to be known as Moderate-Realism , advocates a three-tiered existence of natures such as "human nature". The ontologically prior mode of existence is that wherein human nature is of itself neither universal or particular, but indifferent to each. A second mode is that whereby the nature is itself made particular through existence in reality through contraction via an individual difference. And the third mode is existence in the intellect whereby the concept is universally predicable of numerically multiple particulars. This triad allows Scotus to maintain that (i) "human nature", for example, does exist in the particular human whereby real commonality is accounted for, (ii) that our concept of universals corresponds to actual instances of nature, both undetermined and determined with respect to singularity, and (iii) that universals have a real ontological status 2 independent of the intellect's concept or the particular's nature..
Later he writes,
Scotus will, however, posit a formal distinction, which is made only in the intellect, yet corresponds to the ontologically prior status of human nature. The individual nature itself remains unintelligible, due to the intellect's inability to conceptualize such a radical individuator. The formal distinction, though intellect-dependent, corresponds to actual metaphysical constituents of the individual nature.
One should also mention the summary of a book on Peirce and Scotus up at Arisbe. "The Realism of John Duns Scotus in the Philosophy of Charles Peirce"
Now I've discussed Scotus here a fair number of times. I just bring this up as I'm reading that book on Heidegger's realism and have come to the crucial chapter in Carman's Heidegger's Analytic. There the issue is moderate realism. Now Carman argues against both the kind of realism Putnam espouses, Kant's "epistemological realism" as well as the middle ground of deflationary realism of Fine's NOMA as well as Davidson's holism. I'm thus far not entirely convinced by Carman. (And admittedly this is more a question of how to read Heidegger than a philosophical argument, thus far) But the whole issue of Duns Scotus and his realism, not to mention Peirce and particularly Peirce's treatment of Kant's realism seems quite appropriate.
I'll hopefully touch upon this more in the future as I sort out the ideas and arguments in my mind.