Mentality is often considered naturalistically suspect and in need of a naturalistic vindication, or "naturalization." For many naturalists, Cartesian immaterial minds are the worst case: they are almost invariably presumed to be transnatural entities, beyond any possibility of naturalistic redemption. Steven Horst is typical; he simply declares "Philosophical Naturalism...involves rejection of paradigmatically supernatural entities and properties (e.g., Cartesian souls)." This is unwarranted. As every introductory student of philosophy knows, Cartesian minds were conceived as causally interacting with bodily objects and events, and again as everyone knows, Descartes was taken to task, immediately, for this eminently commonsensical idea. It was his illustrious contemporaries, like Leibniz, who, by denying minds' interaction with matter, placed minds outside the natural world. If we wanted "paradigmatic" supernaturalists about minds from the period, we would do better to mention Leibniz with his pre-established harmony, Malebranche and his occasionalist followers, and others. It may well be that Descartes's idea of an immaterial mind in causal relations to material bodies was inherently flawed, or that as a matter of fact Cartesian immaterial minds do not exist. But that is something that needs to be shown, by a naturalistically acceptable procedure. The point is that Cartesian minds were conceived as part of the causal-explanatory structure of the natural world; if they do not exist, they do not exist as part of the natural world. It isn't as though they are kicked upstairs into a supernatural world and find a home there. The problem with immaterial souls, as with phlogiston and caloric fluids, is that there are no such things as far as we know. It would be nonsense to think that all we found out about phlogiston and caloric fluids was that they turned out to be transcendental, supernatural entities.
"From Naturalism to Physicalism: Supervenience Redux" (Romanell Lecture)
Proceedings and Addresses of The American Philosophical Association 85/2 (2011): 109-34.