Descartes' Theory: The Duality of The Mind and Body

Rene Descartes was a French scientist, philosopher, academician, and mathematician. He is fondly referred to as the father of modern philosophy by historians.

Born in March 1596, in La Haye en Touraine, France, Descartes began his education at the age of 8. When he was 22years old, he bagged a law degree from the University of Poitiers. However, his career as a lawyer was halted when an influential teacher encouraged him to apply mathematics and logic to the problems in the natural world. This action incorporated a whole new chapter in Descartes’ life and resulted in him promoting the development of a new science that was grounded in experiment and observation.

Descartes totally abandoned scholastic Aristotelianism which was popular at the time for his own brand of philosophy. He developed techniques that were useful in analyzing algebraic geometry which earned him credit as the father of analytic geometry. He created an important empirical account of the rainbow and also proposed an account of how the earth and planets were formed. Furthermore, Descartes developed a new concept of the natural world which is still in use today. This concept claimed that the natural world is a world of matter that possesses a few basic properties, and also interacts according to some universal laws. His philosophical masterpiece Meditations on First Philosophy still remains a standard text in most universities’ philosophy department.

Descartes was the first person to formulate the modern version of the mind-body dualism which brought about the mind-body problem. In this article, we will look at his theory of the duality of the mind and body.

What is the duality of the mind and body?

The mind-body dualism has always existed in philosophy. It is a theory that believes that the mind and body are separate from each other in some categorical way. It also believes that the phenomena of the mind are non-physical in nature, in some aspects. In addition, this philosophy states that the mind and body are different kinds of entities which differ in meaning. Therefore, the dualist is one who is against any theory that puts the mind and body together.

Rene Descartes started his investigation into the connection between the mind and body after returning from a robotic display in Paris. He observed that the body behaves like a machine and has material properties. However, the mind is immaterial and does not obey the natural laws. Thus, the only form of interaction the mind and body has occurs at the pineal gland.

Descartes selected the pineal gland as the seat of the soul for some reasons. First, the pineal gland seemed like a unitary organ, and since the soul was also unitary, the match looked perfect. Secondly, he noticed that the pineal gland was close to the ventricles. He believed that the pineal gland influenced the ventricles’ cerebrospinal fluid to act through the nerves to control the body. He also claimed that the sensations the nerves delivered to the pineal makes it vibrate in a sympathetic manner. This vibration then fills the body with emotions and causes it to act.

Descartes’ type of dualism suggests that even though the mind controls the body, there are some points in which the body can also influence the rational mind. Before Descartes came up with his theory, most philosophers thought that it was impossible for the body to control the mind.

The argument for the theory of dualism

In trying to prove that his theory was right, Descartes formulated an argument to support his claim. This argument is based on the belief that the essence of the body is extension, while the essence of the mind is thought. Therefore, the duality of the essences suggests the duality of substances that correspond to the essences. Descartes broke down his argument into seven steps which are as follows:

  • If I can distinctly and clearly see something, then God created an existing something that can correspond to my distinct and clear perception. Otherwise, God would be seen as a deceiver.
  • If I can distinctly and clearly view objects A and B as complete things whose major attributes do not include each other, then God can ensure that A and B can exist away from each other.
  • If A and B can exist away from each other, irrespective of how real or not it is, then they are really distinct and separate.
  • I can distinctly and clearly see the mind as a complete thing which does not require extension.
  • I can distinctly and clearly see the body as a complete thing which does not require thought.
  • On the basis of this, God could decide to allow the mind and body exist separately from each other.
  • Therefore, the mind and body are truly distinct and separate.

From the above argument, we can clearly perceive what Descartes’ theory is all about. He understood that the mind and body possess separate essences that do not interact with each other. This logic shows that when he distinctly and clearly perceives one, he is not perceiving the other secretly. In other words, when he thinks of the mind, he is not thinking of it in relation to the body.

He is also aware that God can separate anything that we can distinctly and clearly perceive. Similarly, since we can clearly and distinctly perceive a body without mind and a mind without body, then God can allow for such an existence. In clear terms, he (God) can allow the mind to exist without the body, and the body to exist without the mind. Therefore, Descartes concludes that the duality of the mind and body is really distinct from each other. And this conclusion formed the basis for his famous sentence “I think, therefore I am.”


We have just looked at the theory of Descartes concerning the duality of the mind and body. Moreover, we have also studied the argument he used in backing his theory. Finally, the central theme of Descartes theory of duality believes that the mind and body are two separable entities which are capable of existing apart.

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