The seventeenth-century French Benedictine philosopher Dom Robert Desgabets (1610–1678) has been taken by many historians as an idiosyncratic but ultimately loyal proponent of Cartesianism in the years following Descartes’ death. As a Catholic cleric aware of the importance of squaring the new philosophical conclusions of the seventeenth-century with Church theology, Desgabets wrote extensively on the ways in which this could be achieved with regard to the most contentious and complex theological Church dogma of the time: transubstantiation. Through an examination of (...) Desgabets’ writings on transubstantiation, this article argues that he was emboldened by his particular religious context and preoccupations to undertake an in-depth theological interrogation and revision of Descartes’ eucharistic thought, which motivated him to offer a more epistemologically and theologically ambitious account of transubstantiation than Descartes himself thought possible or wise. This article therefore uses Desgabets as an example of the complex interplay between theology and “new” philosophy in the early reception of Cartesianism. It shows how this interplay allowed early, theologically minded Cartesians like Desgabets to use the intellectual resources of the Catholic Church to fortify and safeguard the legacy of Cartesianism in a way Descartes himself did not do. (shrink)