I must correct what I wrote in my last-but-one entry. The complete text of Althusius' Dicaeologicae is indeed available in PDF format, as I discovered by perusing the current issue of M&M. Of particular interest in Grabill's introductory essay is his attribution of the origin of the principle of subsidiarity, not to Catholic social teachings, but to Althusius himself and the tradition of Reformed Christian thought:
The research team of Jacques Delors, president of the European Commission during the long and difficult gestation period of the Maastricht Treaty in the European Union, thinks the modern beginning of subsidiarity as a guiding principle of power allocation in plural systems of governance is to be found in a 1571 resolution passed by the Synod of Emden to govern the relationship between parishes and general synods. The researchers attribute the genesis of this political principle to Calvinist “federal theology, Emden and Althusius,” which predates Pope Pius XI’s famous description of the doctrine of subsidiarity in the 1931 encyclical Quadragesimo Anno (nos. 79–80) by nearly three and one-half centuries.