A reductive explanation of consciousness will explain this wholly on the basis of physical principles that do not themselves make any appeal to consciousness. According to materialism, consciousness is the direct result of brain activity. Nonreductivism admits the existence of consciousness as part of the explanation. Nonmaterialism, on the other hand, views consciousness as an essential but nonphysical part of the human being. In order to emphasize the nonphysical nature of consciousness, Chalmers offers a number of convincing arguments against materialism.
The Explanatory argument holds that at most, structure and function can be explained by physical arguments relating to the brain and its connections, and as seen above, these do not sufficiently explain the manifestations of consciousness. It follows that consciousness cannot be explained by physical account. The conceivability argument holds that entities without any consciousness - such as zombies, for example - could exist. All their physical functions would be normal, but personality and free will would be absent. The fact that such creatures might conceivably exist proves that consciousness is nonphysical. The third argument is the knowledge argument. According to this argument, there are truths about consciousness that cannot be deducted from physical fact. This has been elaborated above. If this is true, then the materialist argument is false, and consciousness is not directly or inextricably bound with the physical brain.
When taken in concomitance, it therefore appears that Chalmers and Knapp agree on the general nature of consciousness: Both hold that it is nonphysical, and that, if there are physical connections with the brain, then these are only tenuous. Indeed, Chalmers offers three alternatives to materialism in order to more scientifically, or at least philosophically, explain the nature of the interaction between the physical and the phenomenological.
The most convincing argument when taken in the light of Knapp's arguments could be Chalmer's explication of Type-D Dualism (Chalmers, p.29). The fundamental principle of this theory is that phenomenal properties can affect the physical world, and vice versa. Chalmers also refers to this as "interactionism." In terms of consciousness, this means that the physical and nonphysical properties within the human body interact with each other and affect each other, although they are not of the same nature. What Chalmers refers to as the "microphysical states" are therefore developed by the interaction between the physical and the phenomenological; the physical properties of the brain, and the nonphysical nature of experience.
A further reason for my tendency to favor this view is that it is based upon previous philosophical work by Descartes, in developing substance dualism. This view holds that mental and physical substances are separate, but interact with each other. Indeed, this view also appears compatible with the latest developments not only in philosophy and even spirituality, for lack of a better term; it also resonates well with the nature of physical laws, where there is often no distinct causal link between a law and its fundamental phenomenological cause. Indeed, the author points out the contemporary physics has developed to a point where it can no longer rule out interactionism, but even encourages investigations into the possibilities it offers.
To return to Knapp's view, it is clear that consciousness, personality, free will, and all its associated phenomena exist. To deny this would be to suggest the existence of Chalmer's hypothetical zombies. Human beings have different personalities, likes and dislikes, obsessions and fears, that do not seem in any way dictated by the logic of the physical brain. Hence there has to be a nonphysical quality to explain this.
Chalmer's view of interactionism correlates well with Knapp's passenger analogy. The physical human body acts as a temporary vehicle for the consciousness, the personality - the soul. The question however remains - is it defensible to refer to the consciousness and its phenomenological experiences as the "soul"? This would depend on a person's definition of the term.
The soul could be said to have the following properties: it is nonphysical, it is immortal, and it is spiritual. The latter two have not been proven about the consciousness. While many hold that phenomena such as near-death experiences or the temporary separation of the consciousness from the body during coma or operations serve as proof for the eternal nature of the soul, this is not in fact proven beyond a doubt. The spirituality and immortal nature of the soul are however arguments that could be taken up within the religious rather than the philosophical sphere.
In the light of the above, the most important property of what Knapp refers to as the soul, is that it is part of the human being, but not proved as such to be a physical part of the body. It is nonphysical, but nonetheless influences and is influenced by the body, until death "parts" them. Whatever happens to the consciousness after this remains for religious philosophers to argue.
I believe that it is valid to refer to the consciousness as the soul, because it correlates well with Chalmer's Type D-Duality and its interactionism. Furthermore, there are many concomitant examples in the physical world, and even in the physical sciences, to support the idea of interactionism within the human body.
In the light of the above, I therefore conclude that the nonphysical, phenomenological experiences of the human being can be referred to as consciousness or the soul. It is also the seat of the personality and the human life force. This aspect leaves the physical body when it dies and is buried, although there is no conclusive evidence as to its longevity.
Chalmers, David J. (2002). Consciousness and its Place in Nature. Research School of Social Sciences: Australian National University. http://consc.net/papers/nature.pdf
Knapp, Stephen. (no date available). Consciousness: The Symptom of the Soul. How it interacts with but is separate from the body. http://www.stephen-knapp.com/consciousness_the_symptom_of_the_soul.htm