In this paper, I examine a heretofore ignored critic of Descartes on the heterogeneity problem: Anton Wilhelm Amo. Looking at Amo’s critique of Descartes reveals a very clear case of a thinker who attempts to offer a causal system that is not a solution to the mind-body problem, but rather that transcends it. The focus of my discussion is Amo’s 1734 dissertation: The Apathy [ἀπάθεια] of the Human Mind or The Absence of Sensation and the Faculty of Sense in the (...) Human Mind and their Presence in our Organic and Living Body. Amo’s discussion of the interaction, or lack thereof, of the mind and body hinges on the essential feature he identifies for the human mind—apathy, that is, impassivity. In this work, Amo engages explicitly with Descartes’s writing, which allows us to more precisely see the nature of his agreement and disagreement with the Cartesian metaphysics of mind. I proceed by treating Amo’s five stated criteria for spirit-hood which, in turn, reveal the kinds of causal connections that are possible for embodied spirits on his view. My aim is threefold: To lay out what I take to be Amo’s view of and arguments for the five criteria he takes to be required for a substance to be spirit. To locate Amo’s agreement and disagreement with Descartes. To suggest that Amo’s view on mind-body interaction involves a kind of occasional causation. (shrink)