Although there are many great philosophers who have assisted in shaping the countless different areas of philosophy such as epistemology, ethics, logic, metaphysics, etc, the philosopher that I will proceed to examine is one who, in my opinion, has made one of the most influential contributions to the world of philosophy. Not only has his studies allowed us to observe our intellectual and physical worlds as two different phenomena, but, even more, his studies eventually led to the sharply distinguished subject of philosophy. René Descartes, better known as the father of modern philosophy, has, through his theory of rationalism, enabled us to understand the world to be through the use of reason. Descartes sought to replace the causal model of scientific explanation with a more modern model, this eventually leading to the shift from natural science, metaphysics and theology to empirical scientific methods. Descartes was a French mathematician, physicist and philosopher. His Cartesian dualism has paved the way for a major shift in the understanding of philosophy and physics.

In his time, Descartes’ rationalist was extremely taboo. Not only does he attempt to completely change the mode of thinking in his time, but he challenges previous scientific understandings of the world in claiming that almost everything individuals had believed up to the point of his teachings were false, specifically rejecting the previously championed Aristotelian world-view. In Aristotle’s theory of the intellect, he understands the body and soul as one. The mind and the body did not exist in two special senses, but the individual was instead, made up of form/matter composites. The body is the matter that makes up the thing, whereas the soul is the form of the thing. In this, they are two separate parts of the same thing. In this Aristotelian theory, the material world and intellectual thought processes are not distinct from one another.

Descartes wholeheartedly rejects Aristotle’s notion of an inseparable mind and body, claiming that there is an absolute division between the two. In this mind/body dualism, Descartes states that a world (without God), consists of two substances: the res cogitans (the thinking thing) and the res extensa (the extended thing). Descartes understands the human mind as the res cogitans and the res extensa as matter – that which makes up the world around us. The mind contains a subset of ideas, some which are objectively valid and others which he recognizes as “unclear and indistinct,” these subjective perceptions of which do not allow us to fully understand our reality.

From this, Descartes states that our senses have the ability to deceive us. He uses the specific example of an individual who is dreaming. When an individual is dreaming, they do not necessarily know that they are dreaming. He states that dreams can have the same components as reality, but individuals may not necessarily recognize if they are dreaming. If this is true, then their senses may or may not be manipulating their reality. This leads Descartes to understand that, because his senses can deceive him, he can doubt everything he thinks. The only thing that he can know to be true is his existence, and this is because he has the ability to think that he exists. In this, he coins the term, cogito ergo sum or, “I think, therefore I am.” In this, Descartes recognizes that the union between mind and body would not be complete without our own subjectivity because this allows us to understand what would be beneficial our hurtful to our own being.

Descartes’ theory of mind/body dualism completely collapses previous philosophical beliefs, such as that of Aristotle which sought to understand the individual through the connection between body and soul. In destroying the previous beliefs systems of people, Descartes attempts to rebuild a system of rational in which individuals question everything that they have previously been thought until they can prove it through logic and empirical evidence. Not only is Descartes known for his work as a philosopher, but he is also known for creating the Cartesian coordinate system, which was a major influence in the creation and development of modern calculus.