"Metaphysical interferences": Leibniz, Spinoza and Tschirnhaus on the principle of plenitude

During his epistolary exchange with Spinoza, Tschirnhaus argues the impossibility of deducing the nature of particular bodies from extension alone. This objection lies in his incapability to detach himself from Descartes' substantial conception of bodies as finite parts of matter. Nevertheless, this question becomes obscured by Leibniz's irruption at a crucial point of the correspondence. His interference will transform a physical dispute into a theological one. This paper aims to show that the metaphysical issue detected by Leibniz consists in the radical affirmation of the principle of plenitude, upheld by Spinoza in proposition 16 of the first part of the Ethics, as well as the heretical consequences that follow from it. The examination of the role that Leibniz's critique played in the development of the discussion will allow us to read in a new light both Tschirnhaus' paradoxical attitude and Spinoza's enigmatic and elusive answers.