In this post I'll note some areas of concern I have from an Aristotelian-Thomistic (henceforth just 'Aristotelian') point of view with Kant's B-edition preface. Again, as I said in my first post, this isn't really meant to be a summary of Kant's views, but more along the lines of a set of notes.
One thing which already indicates Kant has a different conception of reality than an Aristotelian realist view is his description of logic toward the beginning. Kant says that logic is "the science that exhaustively presents and strictly proves nothing but the formal rules of all thinking." But a realist will want to ask why logic is defined in terms of its applicability to our thoughts rather than to mind-independent propositions or even objects. After all, since Kant's time, many different logics have been developed, and we can think in terms of any of these if we want to. But this says nothing about which one more correctly describes reality. Of course, what Kant will want to argue is that what I am calling "reality" is actually a product of human cognitive capacities. So the difference to note here between the two views is not so much of whether logic is to be applied to reality, but rather, what reality refers to.
A second point of interest is Kant's discussion of mathematical knowledge at Bxii, where he takes as his example that of a Euclidean triangle. Kant uses this point to illustrate how he thinks it is that we acquire mathematical knowledge. What I would focus on though is his view that, more generally, Euclidean geometry is necessary. For Kant, a judgment is necessary if and only if it is a priori. The problem is that we now know that Euclidean geometry is not, in fact, necessary, since it doesn't even accurately describe the physical universe. So either euclidean geometry is not a priori or Kant was wrong to include necessity as part of something's being a priori. But it seems rather clear euclidean geometry was formulated a priori if anything was. So it must follow that not all a priori cognitions are necessary. But this is okay for the Aristotelian. The Aristotelian method of doing metaphysics or science has never been equivalent to discovering necessary truths which are wholly a priori; rather, it is empirical. We can delineate what is metaphysically possible and impossible through a priori reasoning and we see whether our theories correspond to empirical reality.
Kant's view of the a priori goes with his view of metaphysics. He defines metaphysics as "a wholly isolated speculative cognition of reason that elevates itself entirely above all instruction from experience." Not according to an Aristotelian view however. As Aquinas states in 'De Veritate', "Whatever is in the intellect was first in the senses." Of course, the reason Kant wants to make metaphysics a wholly a priori discipline is because he wants the certainty which he thinks the method of previous thinkers cannot provide. In his own words Kant thinks that "up to now [i.e. up until Kant] the procedure of metaphysics has been a mere groping, and what is the worst, a groping among mere concepts." But the Aristotelian wants to ask why it has only been a "mere groping among concepts"? For one, the metaphysician does not need to limit the scope of his inquiry to concepts, at least if we don't hold to the view that metaphysics must be a priori. As regards "mere groping," admittedly, we cannot be absolutely certain our metaphysical theories are true; but this is a far too strict condition upon knowledge which, were it not for Descartes, we would not think was necessary.
In the next post I will focus on the second half of the preface, examining Kant's solution to the problem of metaphysical knowledge as he sees it.