Thomas Nagel has some interesting ideas regarding the mind-body issue as he focuses extensively on the issue of consciousness. The philosophical idea regarding dualism is, in its most basic definition (the separation of the physical and the non-physical), an easy concept to grasp, however when one delves deeper into philosophy it becomes a concept that becomes increasingly complex to rationalize. In "What Is It Like to Be a Bat?" Nagel tackles the subjective qualities of a being so as to counteract the physicalist point of view, which minimizes all of the functions of the mind to merely physical components. The primary concern is the consideration of how subjective experience cannot be examined by objective means, and therefore not be examined by scientific means.
Nagel's argument considers how conscious beings have experiences, and more importantly that those experiences can not be quantified or completely understood on a subjective level by any other being than the one "doing" the experiencing. If we are conscious beings, then there must be something it is like to be a conscious being. One can describe, perhaps even in great detail, general types of experience based on physical attributes and behavior; however one can not know every intimate detail about a particular being. In many ways, Nagel's argument is essentially an argument of fantasy verses reality. We have the capacity to conceptualize what it is like to be a bat, however since we cannot really be bats (and therefore have the experience of a bat); we can only truly examine another conscious creature's experience from our own perspective. It would seem then that there is something about being a particular conscious being that exists outside of the realm of the physical, though not necessarily in such a way that is completely separate from the body.
I find Nagel's argument to be very intriguing, though I hold closely to my own physicalistic view of the world. I cannot deny that he has, minimally, left me with very much to ponder with regard to the mind; however he has not really considered what it means for beings that are conscious to have these conscious experiences. A question such as "Why us and not some species of plant", for instance, is one that comes into my mind without much hesitation. Additionally, I feel that a requirement of consciousness is the inability for that aspect of a being to become non-existent. Nagel indicates that consciousness is essentially an element of a being that does not strictly require physical qualities to be manifested, which seemingly then must imply that there is something that will continue to exist whether or not a physical being continues to exist. The primary problem I have with Nagel's argument is that he does not explain what occurs when the physical body becomes non-existent if there is truly a mind that exists, at least in part, separately from the body. Lastly, he does not seem to express why it is important for one conscious being to have the capacity to subjectively experience another conscious being's experience.
The common knowledge that there will ultimately be death for every conscious being that exists forces me to question the true nature of consciousness. Folk psychology and theological ideas would imply that the mind/soul continues to exist even after the death of the body. If one believes the ideas provided by these sources, than an acceptance of Nagel's argument (and by extension at least some form of dualism) makes sense with little to no problem. For myself, however, death is ultimately the end for all conscious experience; which in itself serves little purpose except to allow human beings and select higher animals to dominate the evolutionary food chain. In some ways, the mind has the functionality of an individual home computer. One can store data and collect new data, and in some ways it may be possible to perceive a computer hard drive as an extension of one's self (as it will likely contain many vital pieces of data that one requires to function, such as information regarding ones bank account). It may even be possible to maintain a computer for a relatively long period of time. With that said, it is very likely that in due time the computer will run its course, crash, and in the end become dysfunctional and ultimately discarded by its owner. If one then views the mind as a computer, then it is inevitable that the mind will cease to function when an individual being dies. For myself, the physical brain is ultimately the "hardware" and the mind is simply downloadable "software" from the internet. All of the data is then stored in one physical location to be deleted at the moment of death. There is seemingly no continuation of the mind in any way that can be separate from the body.
Human beings and some select higher animals have evolved in such a way that we now have the capacity to rationally organize our thoughts and feelings, yet we are still driven by the same primal instincts like any lower creature. As superior to other beings as we would like to think of ourselves, we still act for the purpose of sex, power/dominance, food, and similar issues. In a way, the mind has done nothing but cause human beings to become increasingly foolish and have the capacity to create ways to exploit our internal drives so as to cause other beings to suffer. The superior mind serves little purpose if we do nothing with it but ultimately act for the same purposes as lesser organisms. Thomas Nagel's argument presented in "What is it like to be a bat?" is undeniably intriguing, however it only begins to touch the surface of a much more complex concept of conscious experience. Though I fervently disagree with his perspective in many ways, I have much respect for his ability to express his opinions in writing so eloquently.