The 17th century French philosopher and mathematician René Descartes was a dualist rather than a monist. He argued that there are two fundamental principles that compose our world as opposed to just one. In the monist’s view there is only the physical, but in the dualist’s view there is the physical and also the non-physical. The latter is most commonly understood as the spirit, soul, or mind (a separate entity other than the physical brain).
Descartes’ first argument for his proposition of dualism is a famous one. He claims that one can doubt whether or not one has a body (physical essence), but one cannot doubt whether or not one has a mind (non-physical essence). This concept is captured in his famous quote, “I think, therefore I am.” It would be a logical fallacy for one to doubt one’s own existence. In order to doubt, one must have a mind to do the doubting. An individual can doubt the existence of another part of his body, such as a hand or foot, but the action of doubting the existence of the mind requires one has a mind in the first place. This is not the case for a hand or foot. These appendages are not essential to the act of doubting itself.
This argument is a very appreciable one. From this, Descartes concludes that there must be two essences in the universe, those being the aforementioned physical and non-physical. In Descartes’ opinion, the argument of indubitable existence proves these two essences/principles exist. We know the physical world exists because it is what we are inhabiting at this very moment. Second, we know the mind exists because it has shown to be separate from the world of ordinary matter, and its very use verifies its existence to the user.
The argument is a clever one, but I think it could be expanded upon. This expansion could also possibly result in a conclusion very different from the one Descartes intended. If, “I think, therefore I am,” is enough to show that the mind exists, isn’t, “I feel, therefore I am,” enough to show that the body exists? If the brain’s sensation manifests itself as thought in our conscious experience, how is this different than our other Aristotelian senses manifesting themselves through different physical sensations?
Although I enjoy Descartes’ argument, I find the mind identity argument to be more superior. One could attack my proposition above by saying, “It is not sensation that proves the existence of an organ. The mind’s ability to doubt shows that only the mind’s existence can be absolutely concluded.” But, why does this conclude the existence of a mind, and not just a brain? If thoughts are the physical sensations of the brain, and perceptions of touch, taste, and smell are the sensations of other organs, then this doesn’t demonstrate the brain as unique in the sense it is non-physical. One must assume dualism before the argument starts to arrive at the conclusion that the mind and brain are two separate things.
Until evidence or a different philosophical argument suggests otherwise, the mind identity seems to be the more rational conclusion. Sensations are the result of the natural world, and many of them can be explained in depth. Even Descartes acknowledged that there are interactions between the physical and what he believed to be the non-physical. Music can alter a person’s mood, and thoughts can alter a person’s physical motions. He admitted the interactions can go both ways, but it appears that the unique physical behavior of the brain was misinterpreted as more than the physical. Just because we do not have a full understanding of the nature of the brain does not mean it is beyond nature.
If I know my mind exists because I can think, then I know my eyes exist because I can see. All these various sensations are channeled to the brain, and all those perceptions are made possible by the brain, including the thoughts of the mind. Our cranium is a remarkable feat of our biology, but I am cautious before I conclude that it is somehow more than just natural. After all, isn’t it biased to conclude that the brain is unique because you are using it? If marine life can contemplate its existence (as it has been suggested), would it be erroneous for it to conclude that it is beyond the physical, simply because it can acknowledge the physical?