In the literature on Anselm, I’ve noticed what seems to me to be a real anxiety to make sure that Anselm isn’t “really” trying to get all the way to the necessity of the Incarnation by “pure reason.” The reason this explanation is necessary in the first place is that Anselm certainly appears to be doing that and doesn’t seem to view the attempt as problematic on a methodological level. In doing so, he is following in a proud tradition — for instance, Gregory of Nyssa’s “Great Catechism” is able to get to the Trinity and even to the creation and fall by means of something like the common sense of the Hellenistic world, though he recognizes that the Incarnation is going to be difficult to swallow. His general principle is to use Scripture for those who respect Scripture, and reason for those who accept only reason. Convincing the former is thought to be easier (though the historical record doesn’t seem to bear that out), but there isn’t a sharp division between the two that I can see.
I think that the reason for the anxiety about Anselm’s approach is that people are reading it in terms of Aquinas’s nature/grace distinction — i.e., reason can get you to a certain point (where Aristotle winds up), and then you need revelation, which is not contrary to reason but whose contents couldn’t be predicted using reason alone. The Trinity, for example, is firmly on the “revealed” side of this distinction, yet Gregory and Anselm both appear not to be worried about the fact that their reasoned argument has gone way over the line.
The reason for their lack of concern is probably that that line wasn’t a big concern of theirs, and we don’t need to read them anachronistically as though they knew about the nature/grace problem and were really concerned not to be doing something like “natural theology” because that would be somehow impious. Instead, maybe we should read them as doing what they’re actually doing — that is, assuming that the world described in Christian revelation is actually this very world where we are. If that is the case, then of course reason should be able to recognize the inner necessity of God’s actions in the world, because God is after all acting in this very same world where our reason finds its home.
I have a bunch of things that I want to say here but can’t fully support yet. For instance, I object to Aquinas’s two-tiered system first of all because it’s so inelegant. Another thing: maybe Barth’s polemic against “natural theology” should’ve gone further and also rejected the kind of “revealed theology” that’s defined in opposition to “natural theology.” Etc. I’m aware that there are all kinds of nuances that I’m not capturing here — sorry about that.
An und für sich 
That’s a really interesting direction re. Barth. You should read the second part of vol. 2.1 (especially the final part of section 31 (part 3)) – In this section, Barth seems to be doing something very much akin to what David Bentley Hart is doing in the beauty of the infinite (which is ironically, in some places, a polemic against Barth) – viz. developing a notion of the infinite (in this case ‘eternity’)which is not parasitic upon time as either univocity or negation but in terms of ‘real time’ – in this sense, I think Barth did go further than a polemic against natural theology which remained reliant upon the rejection of natural theology for its own survival. Check it out!
I’ve read that part of the Dogmatics, but I’m not quite seeing the connection you’re making — why is eternity the key concept here? (I’ve also not read David Bentley Hart and am indeed kind of boycotting it.)
Oh – simply because this is where I think we have Barth’s first hint of his own ‘anologia entis’ (although it’s really more an ‘analogy of being’ because it’s fairly different to the AN of Przywara or von Balthasar) – so we have Barth’s notion of the overcoming of Nature and Grace dichotomy or at least how the two should be conceived of together. I’m not sure whether or not you’re critiquing Barth’s revealed theology or critiquing his own critique of natural theology – I’m simply saying, I don’t think Barth’s revealed theology was a simple negation of natural theology. And I think this is most explicit in the section on the Eternity and Glory of God!
what you’re describing in your last paragraph is what Milbank wants from H. de Lubac and Przywara, although I think that they cannot be squeezed in that way. it is also one of the reason that he finds it so easy to dimiss Barth. There are many reasons to be nervous about Barth but this one doesn’t seem that interesting to me, primarily because debates about what is ‘natural’ and ‘revealed’ turn out to be so uninteresting and debatable and because these terms are usually meant as rhetoric flourishes or conversation-stoppers. but such a position is probably just intellectual laziness on my part.
One thing that I’ve come to think in my own development of a non-theological use of natural theology is that the natural-revealed dichotomy can be made productive if you think of the two terms as a duality analogous to the wave-particle duality in quantum physics. This means I’m often confused as a natural theologian or one who wants to get rid of revelation, but really I’m not.
a further difficulty with the natural-revealed distinction is that more sophisticated accounts of the natural knowledge of God also claim that this knowledge stems from God’s active revelation within nature (usually understand as either in the cosmos, or in an incohoate knowledge of the law, which Kant’s starry skies and moral law within basically secularized). There are exegetical objections to this reading of Romans, but the text has been used in this way.
Natural knowledge of God, as traditionally understood, still depends upon revelation, and this distinction then leads to the debates regarding what is the actual content of natural knowledge of God and revelation, and here is where Roman Catholics, Lutherans, and Reformed folk differ on what the material content of natural knowledge of God is. And, of course, different accounts of what constitutes natural knowledge of God (or natural law) hardly makes such an endeavour seem worthwhile to those inclined to disbelieve in it.
Jon, Your original comment would’ve been way better if you’d replaced “Check it out!” with “But don’t take my word for it!”
Ha! Why should I take your word for it?