To clarify, it seems to me that Brennan is quite ably articulating and explicating a particularly vigorous and metaphysically robust version of subsidiarity often associated with Catholic social teaching, and particularly the neo-Thomist revival of the previous two centuries. My quibble, and I’m not sure if it amounts to much more than that, is with the idea that this is identical to “what subsidiarity means in Catholic social doctrine, period.”
In the papers linked in the previous post I do make more specific claims with respect to subsidiarity in “other” traditions, particularly the Reformed. But given the shared medieval (and even to a great extent the early modern) background and the diversity there, I do wonder whether that more robust, ontologically-freighted version of subsidiarity is the only version at play in the specifically Roman Catholic tradition, either before or after 1891.
Thus, writes Brennan,
subsidiarity is often but erroneously described as a matter of devolution or smallness of scale. In Taparelli’s thought, however, and, in turn, in Catholic social doctrine, it is neither. Pace much modern political theory, power is not all held at the top in the first place, so the possibility that subsidiarity is a devolution norm turns out to be based on a fallacious premise; smallness, furthermore, is not per se good (or bad).
Later Brennan reiterates the point: “Commentators who treat subsidiarity as a matter of devolution or simple smallness of scale overlook the deep ontological springs of the principle.”
I admit that by the time we get to the late nineteenth century that different, although perhaps complementary, visions of subsidiarity came to be associated with various traditions, e.g. Roman Catholic Social Teaching and neo-Calvinist social thought (e.g. sphere sovereignty). As I put it in, “A Society of Mutual Aid: Natural Law and Subsidiarity in Early Modern Reformed Perspective,” there seem to be at least two basic models in play. One is deductive, ontologically hierarchical, and top-down. The other is inductive, functionally hierarchical (at least possibly), and bottom-up. These are not necessarily exclusive models, and give rise to a wide variety of emphases and articulations of the doctrine. But even if the latter model is rather less metaphysically-rich than the former, I think it still warrants being called subsidiarity, even if it is described as thin rather than thick (mere subsidiarity, perhaps?).
So to say that something like a (neo)Thomistic version of subsidiarity is the only one that is really subsidiarity is akin to saying that only a (neo)Thomistic version of natural law is really natural law. This kind of argument is not historically tenable. But even if the claims are limited with respect to the modern articulations of subisidiarity (or natural law) in the Roman Catholic encyclical tradition, such claims seem overly restrictive and narrow.
That is more of a hunch, I suppose, than a fully defensible thesis, and I’m quite happy to be corrected and instructed by those, like Brennan, who know “what subsidiarity means in Catholic social doctrine, period,” far better than I do.