From this he draws the conclusion that since he can doubt the body but not the mind, the latter must be known with greater certainty than the former. Descartes' underlying assumption in this argument is that the mind and the body are two distinct substances. Descartes then proceeds to state that the mind possesses the property of indubitable existence, while the body does not. I grant Descartes his claim that the mind and body are separate entities, however I think he came to a conclusion too quickly. For example, one might doubt that Bruce Wayne is a masked vigilante, but one cannot doubt this about Batman. It does not follow that they are therefore two different entities. Therefore, Descartes overlooks the possibility that his mind might simply be his brain, and therefore a part of his body. Likewise, if Descartes wants to claim that his mind and body are two different substances, he must address the problem of how one can causally interact with the other. For example, if you stub your toe, there is a sensation of pain that the mind is said to experience. But this makes no sense since the mind cannot properly be said to experience pain if it is, as Descartes supposed, an immaterial substance. Furthermore, what is certain about pain is that it cannot be a mental experience because pain is only known through the central nervous system, which in turn is a