In this thought-provoking discussion, John Heil, Professor of Philosophy at Washington University in St Louis, tackles the perplexing concept of Cartesian Transubstantiation. He delves into the clash between Aristotelian and Cartesian metaphysics, unpacking Descartes' unique interpretation of the Eucharist. Heil critically examines how transubstantiation conflicts with Descartes' views on substance and accidents, prompting a reevaluation of traditional church doctrines. This engaging talk blends philosophy, theology, and metaphysics in a captivating exploration.