Philosophy of mind
There are a number of different schools of thought generally addressing the philosophy of mind, including dualism, monism, behaviorism, identity theory, eliminative materialism, and functionalism.
Dualism is thought to be the most common, natural view of the mind-body relationship. There are many different types of dualism. In it's most common form, substance dualism, dualists argue that the world is made up of at least two distinct substances: the material and whatever makes up the mind (generally, but not always, called the spirit). Nobel Prize winner John Eccles is a proponent of dualism.
Monism refers to the philosophical view that there is only one type of material. While this could be physical (see: eliminative materialism and identity theory), monism is generally used to refer to the school of thought where only the spiritual substance exists. These monists are often philosophical skeptics: because they think, they know the mind exists, but everything else could be illusory.
Behaviorism is the philosophical school (closely related to the psychological school) that holds that there is no such thing as a mind. Instead, they replace what we call minds with descriptions of behavior.
Identity theorists argue that mental states (such as the feeling of love) are identical with physical states (such as brain activity in the parietal lobe).
Eliminative materialism is the argument that our concept of mind is misguided from the start. Our 'folk psychology' describing emotions and sensations is full of bad descriptions, and further developments in neuroscience should eliminate talk of these mental states.
Functionalism is a school of thought that is not explicitly dualist or materialist. Functionalists argue that what is important about a mental state is the function it serves. One consequence of functionalist philosophy is that there could two races of humans that appear identical to each other. One group, called the identity theorists, are purely physical beings who feel like we humans do. The other group, called the dualists, are a combination of physical and mental substances who feel like we humans do. To a functionalist, pain in one group is the same in the other group, since it serves the same purpose as it does in humans in both. Although functionalism is open to dualism, most functionalists take a materialist route, generally along the lines of identity theory.