This is such a fascinating subject, I hardly know where to start. I actually have two degrees in this exact subject-- I studied analytical philosophy, but more specifically my specialist subject was what Philosophers call "The Mind/Body Problem".

In short-- What is the relationship between the physical thing, the body (or brain) and the apparently non-physical thing, the mind (or soul)? How can you resolve the fact that the two things are very different in nature, but seem to depend so intrinsically on one another.

---------- Post added 05-06-2013 at 04:25 PM ----------

The Philosphy of Mind typically focuses on three major positions that divide the possibilities, and from there theorists tend to find nuances within those broad areas, or occasionally theories that sit outside or straddle them.

Dualism - That mental phenomena are non-physical, and the mind and body are not identical. (Such non-physical minds are often call "souls" in the Philosophical context.) The most famous dualist is Renee Descartes, so you'll see a lot of talk of Cartesian Dualism.

Materialism - That the only real entities are physical ones (matter and energy) and the mind is just an expression of the physical body. Also sometimes called "physicalism".

Idealism - In this context, that the only real things are mental ones. That the physial world doesn't truly exist.

Of course, these aren't the only options by any means, but I think they interestingly sketch out the territory. When considering what you believe about the relationship of the mind to the body, it may help to consider which of these comes closest.