Demon, Brain, Soul

One popular modernization of Descartes is the 'brain in a vat' interpretation of his 'evil demon' scenario. He proposes the latter to explain the possibility that the existence of one's own body can be doubted--it might be an illusion produced by a evil demon. Analogously, a brain in a vat, located in a laboratory, could be stimulated to create the illusion of the possession of a body. Now, the evil demon scenario is a pivotal element in Descartes' attempt to prove the Immortality of the Soul, which entails the possibility that the Soul can survive the death of the Body. For, that the existence of the Body can be doubted, whereas that of the Mind cannot, provides Descartes with the decisive separation of the two. Perhaps the soundness of his argument is questionable, since it entails equating 'I am not certain of my corporeality' and 'I am certain of my incorporeality'. Regardless, the modernization undercuts Descartes' purpose--a brain in a vat is still corporeal--so that even if it does explain how the perception of one's own body is illusory, it falls short of accomplishing what Descartes requires at this juncture--the dubitably of any corporeality whatsoever. Such an abstraction from the importance to Descartes of the thesis of the Immortality of the Soul is not a isolated modern case. For example, Sartre seems to completely ignore it in his critique of 'I think, therefore I am'. Furthermore, arguments often known as 'Refutation of the Idealism', and 'Proof of the Existence of the External World', are ridiculed by Moore and Heidegger, without any evidence of recognition of the roles that they serve Kant in his argument against Descartes regarding the Immortality of the Soul. That Sartre--in-itself vs. for-itself; Moore--natural vs. non-natural; and Heidegger--beings vs. Beings, each inherit Cartesian dualism, is perhaps evidence of the shallowness of such presentations.