The mind-body problem is one of the most important and difficult questions faced by philosophers since ancient times. It defines the relationship between our ?mind?, which can also be thought of as our ?soul? or our consciousness and awareness, and our ?body?, which is the physical part of us. Simply put, the question is this: are the ?mind? and the body are two distinct entities, or are they joined by a common unifying ground, with our thoughts, self-awareness, knowledge and other ?mental? attributes dependent on our corporeal beings and our body requiring our mental capabilities to survive? Is our mind something capable of existing on its own or does our physical end entail the end of our mind as well? Also known as dualism, the question has been mentioned in the writing of Zarathushtra dating from 6 BC and has also been discussed by Plato and Aristotle. It was, however, Rene Descartes? work regarding the subject that has been the most thorough and well-known. According to him, the mind was a non-physical entity. It did not obey the laws of physics ? in fact, it was completely different from any form of physical object that we are familiar with; it simply existed (Passions of the Soul, 1649). He further believed that while the body was controlled by the mind, it could also act entirely of its own volition, such as when sick or when overtaken by a strong emotion. The mind and body were, according to him, connected at the pineal gland, which is located in the brain. As we can see, the mind and body, according to Descartes, are two distinct things with only a small degree of control over each other. There were several inaccuracies in Descartes? ideas. Perhaps the greatest failing in these early assumptions was his belief that that a physically non-existent mind could control a corporeal entity. Even if the pineal gland was supposedly involved in making the connection between the mind and body, exactly how could the non-material mind influence or affect it? Descartes later admitted to Princess Elisabeth that he did not know exactly how the pineal gland was involved in this process. He further believed that only humans had minds, and so only they had pineal glands. He made the mistake of not giving much importance to the medical inaccuracies in his ideas, which is understandable since medical knowledge at that time was cursory. Several later branches of philosophy aim at overcoming the shortcomings of Descartes? otherwise profound ideas which were way ahead of their time. Epiphenomenalism, for example, holds that our intentions are influenced by our physical world, but our various states of mind do not influence the body. The various physical things in this world that we interact with affect our moods, our knowledge, our feelings and other faculties associated with our mind, but these faculties by themselves do not have an effect on the physical world. Epiphenomena literally mean ?side-effects?. This view aims at removing the vagueness of Descartes? idea that the body and mind are only connected partially through an organ? it defines the mind more precisely and does away with the unnecessary job of determining exactly which part of the body is concerned with the mind, something even modern science is still studying. Monism and materialism are two similar views which propose that everything in this universe (in fact the universe itself) is unified and therefore really is just one entity with several different manifestations. In terms of the mind and body, such views state that physical things are the only things that exists (this is the true definition of materialism, which is just a branch of monism). Therefore, the body is all that exists of the human being, and the mind can also be explained in terms of the body ? it does not exist as a separate entity. This takes a somewhat scientific approach to the problem by stating that the mind is simply an extension of the brain, just as the work that we do is done by our body and is nothing by itself. It reduces the need of defining the mind and body as two separate entities, and enables us to think of them as simply different parts of the same thing ? the human body. Thus we can see how these later theories help smooth out the errors in Descartes? assertions and give us a clearer idea of the relation between our mental and corporeal beings.