Between 1621 and 1626, the soldier-historian Philip O’Sullivan Beare authored treatises to motivate Catholic powers toward greater intervention in Ireland, and to defend his country’s honor more generally. Moving beyond political theology, the author’s unfinished manuscript Zoilomastix incorporated natural history and astronomy. The current article draws attention to a previously overlooked fragment wherein the Irishman considered contemporary debates on the structure of the heavens. It first considers the material history of the fragment, before exploring the influence of continental pedagogic and military networks upon the author. The paper then presents evidence of O’Sullivan Beare’s adherence to Thomist, Bellarminian cosmology, and of his disagreement with Clavius and Galileo, via Jacques du Chevreul’s 1623 commentary on Sacrobosco’s Sphere. Contrasting the fragment’s contents with the cosmogony published in the author’s Patritiana decas (1629), it demonstrates that these exegetic readings were part of the author’s wider strategy for “making truth” amidst shifting political, confessional, and cosmological paradigms.

The studies of Bonaventura Cavalieri’s indivisibles by Giusti, Andersen, Mancosu and others provide a comprehensive picture of Cavalieri’s mathematics, as well as of the mathematical objections to it as formulated by Paul Guldin and other critics. Issues that have been studied in less detail concern the theological underpinnings of the contemporary debate over indivisibles, its historical roots, the geopolitical situation at the time, and its relation to the ultimate suppression of Cavalieri’s religious order. We analyze sources from the seventeenth through twenty-first centuries to investigate this relationship.