This paper, an attempt at an institutional history of ideas, compares patterns of reproduction of scientific knowledge in Catholic and Protestant educational institutions. Franciscus Eschinardus' Cursus Physico-Mathematicus and Jean-Robert Chouet's Syntagma Physicum are examined for the strategies which allow for accommodation of new contents and new practices within traditional institutional frameworks. The texts manifest two different styles of inquiry about nature, each adapted to the peculiar constraints implied by its environment. The interpretative drive of Eschinardus and a whole group of “modern astronomers” is here seen as pushing beyond the traditional task of “saving the phenomena”, towards celestial hermeneutics which is thoroughly experimental and mathematical. In spite of the insistence on physical interpretation of celestial phenomena, Eschinardus’ astronomical discourse is yet constrained by a complex game of intellectual-political considerations. Commitment to the Thomistic organization of knowledge, which sets a boundary between a science of motion (physica) and the “geometry of heavens” (mathematical astronomy), suppresses any impulse to ask about the mechanical causes of celestial appearances. The Copernican cosmology is thus rejected qua an attempt to cross this guarded boundary. Chouet in Geneva, by contrast, frees himself from these constraints on the organization of natural knowledge. By strictly separating philosophy from theology, he can combine physics and astronomy, favor a Copernican cosmology and adopt a Cartesian mechanistic worldview. Moreover, unlike the Jesuit Eschinardus, Chouet seeks to explain natural phenomena in terms of causes, rather than just interpret them. Yet he does so within a philosophical discourse largely scholastic in nature, which best suits the conservative institutional framework in which he teaches. Whereas the Jesuit Eschinardus employs a new type of discourse without severing his links with the traditional Thomistic worldview, the Calvinist Chouet adopts a new Cartesian worldview and adapts it to a largely traditional type of discourse.