In Metaphysical Philosophy, there exists what is known as the mind-body problem. The Mind-Body Problem the debate over how connected the mind and the body are. We know that the physical brain is an organ of the body that interacts with the physical human body. Yet do the thought processes that we have, which are so far undetectable by modern technology, have any connection to our physical brain? Are the thoughts, feelings, fantasies, and ideas that we have only interpretations of chemical reactions and physical stimuli? Could the mind be our soul; completely separate from the brains functions?
In this Mind-Body problem, there are two different solutions to the problem. The first solution is known as Mind-Body Dualism. Dualism, first proposed by the philosopher Renee Descartes, postulated that the mind and the body are two separate things (221). Descartes proposed the most common form of Dualism, known as Interactionism. Interactionism is essentially the idea that the mind and the body, while being two separate things, casually interact with each other (216).
Physicalism on the other hand is the idea that the mind is nothing more than a series of physical interactions, and our thoughts and the self is nothing more than chemical interactions being interpreted by the brain (216). Within Physicalism, there are various versions. Reductionism, Eliminativism, and functionalism are all variants of Physicalism that take the same stance, but in different ways. Reductionism and Eliminativism are essentially the same; though they differ in that Eliminativism does not recognize words or ideas associated with the concept of the mind wile Reductionism does recognize those words. Functionalism proposes that the mind works similar to a computer in the same way that a computer can turn a series of electrical sparks and translate that into a virtual game (217).
Metaphysical materialism is the monistic claim that the only reality that exists is a physical reality. What this means is that materialists believe that reality is a physical based process where things such as the mind are chemical and electric reactions. To the materialist, the mind is only the brain and a non-physical mind does not exist. This is essentially the same as Physicalism and the two are generally interchangeable.
An example is a rose. The materialist believes that the rose has sharp thorns, even if he has no hands to feel the rose with. The idealist, however, would say that the rose thorn is not sharp in reality because in his reality he cannot feel that it is sharp. For one, reality is what is physical. For the other, reality is what is mental.
The third position on the Mind-Body Problem is Idealism. Idealism is the thought that the body and the physical realm does not exist, but that only our mental states exist in reality. In essence, Idealism is the exact reverse of Physicalism (217). Metaphysical idealism is the monistic claim that the only reality that exists is one based upon a mental or spiritual perception. Reality is not physical in nature, but is completely mental, and the objects that we interact with exist in our own mental realities.
Source: The Philosophical Journey by William F. Lawhead 5th Edition ISBN:9780073535876