Subsidiarity is that principle by which we respect the inherent dignity and freedom of the individual by never doing for others what they can do for themselves and thus enabling individuals to have the most possible discretion in the affairs of their lives.Now, the reason this quote strikes me is because it isn't, really, the definition of subsidiarity. While this extrapolation may be just - while the meaning the Bishops derive from the teaching could be argued to be implicit in what has been said about the principle - I'm not aware of a precedent for applying subsidiarity in a lateral way like this. Now, in context, the letter is speaking about the higher order of the State not interfering in the functions of lower orders (such as the health care industry privately run, or families, etc.), and that notion is a strict interpretation of subsidiarity. But the sentence above doesn't really say that. It doesn't make clear the traditional "vertical" understanding of this principle, and seems to argue it on a "horizontal" plane.
The reason I bring it up is that it interests me. I wonder if it's fair to bring this horizontality into the discussion of subsidiarity, or whether a separate principle within the realm of solidarity is really meant for this application. Again, I'm not concerned with the broader point in the context of the letter, but I'm concerned with the exact meaning of this quotation (which, such as it is, is actually irrelevant to the context in which it is found if you want to get technical). Personally, I prefer keeping very closely to the Church's traditional language on subsidiarity and its application primarily to the question of the justice due to individuals on the part of the whole of society and the political organizations therein. But the "we" in this quotation might be, say, a next door neighbor. And is that relationship, and the demand "not to do for the other what the other might do himself," properly governed under the principle of subsidiarity as it has been explicated in Magisterial writings? Thoughts, anyone?