body as a geometrically defined region of space includes the possibility of its infinite divisibility, but the mind, despite the variety of its many faculties and operations, must be conceived as a single, unitary, indivisible being; since incompatible properties cannot inhere in any one substance, the mind and body are perfectly distinct. (Med. VI) This radical separation of mind and body makes it difficult to account for the apparent interaction of the two in my own case. In ordinary experience, it surely seems that the volitions of my mind can cause physical movements in my body and that the physical states of my body can produce effects on my mental operations. But on Descartes's view, there can be no substantial connection between the two, nor did he believe it appropriate to think of the mind as residing in the body as a pilot resides within a ship. Although he offered several tenatative suggestions in his correspondence with Princess Elizabeth, Descartes largely left for future generations the task of developing some reasonable account of volition and sensation, either by securing the possibility of mind-body interaction or by proposing some alternative explanation of the appearances....
