Descartes’ Dualism and the Mind/Body Problem

Descartes formulated the cogito, the idea that because one thinks, they must necessarily exist (“I think therefore I am”). This assertion forms the foundation for his system proving that our sensory perceptions are reliable. This fact is essential for science. Nevertheless there are problems with his system, and there are serious consequences that follow from his propositions.

Descartes is one of the most influential thinkers of modern time. He lived from March 31,1596 – February 11, 1650, and was not only an innovator in philosophy, but also made important contributions to mathematics and physics.

Descartes Rationalism

Descartes was a rationalist. Rationalism is the idea that real knowledge can only be known through reason. This position is not as popular today as empiricism (e.g., the idea that things can only be known through experience). Yet even today there is a tension in science between the rationalist and the empiricist positions. For example it is not known how much of human behavior is innate (e.g., based on rational principles), or is learned (e.g., empirical).

According to Descartes reason exists in the mind independent of the body. The mind according to the rationalist lives on after the body perishes. The body is corporeal and is therefore temporal and spatial. On the other hand the mind is atemporal and aspatial.

According to Descartes knowledge is only reliable if it can be understood through reason by the mind. Knowledge that is known through the body, the five senses, cannot be relied on at all. Examples might be the illusion of water in a desert, or as Descartes states, how do one know that what is perceived is in fact reliable since one may be in fact sleeping? The movie, The Matrix, borrows from this idea of the senses being unreliable. The worldly action in the movie is actually the result of ideas being pumped into the protagonists brain by machines.

The Importance of Descartes Cogito

Descartes wanted to find a way where one can know the sensations of the world are not misleading. Previous to Descartes were the medieval philosophers known as the scholastics. Descartes did not agree with this philosophy; he believed it was the result of unbridled speculative reason, and as a result, he believed that it was unnecessarily complex. So not only could experience be misleading, but unbridled rational speculation was a threat too.

Descartes was a skeptic, and his system set out to reject anything that can’t be determined necessarily veritable. Under this maxim, everything that could possibly be denied as being veritable would in fact be discarded. Descartes thought that this would address the problem of the scholastics, who came to conclusions that did not inerrantly follow from their propositions, as well as the empiricists, who were subject to being mislead by the senses.

The thing that one is most certain of is that one exists. How do people know they exist? People know they exist because they think. Therefore, one has the Cartesian Cogito – “I think therefore I am.” It is impossible to think without existing, that is that which exists necessarily follows from the premise of thought. This is the foundation of Descartes’ system.

He further explains by asserting that one has an idea of perfection for those whom are flawed. How can something flawed conceive of something perfect? The only answer is that which is known through reason is in fact perfect. And how could anything that exists that is perfect be other than God? This is referred to as the Cosmological Argument and serves as what has historically been an effective proof for the existence of God.

If God exists and God is perfect then God would not deceive, so one can know that what one perceives is, at least in some instances, reliable, that is God does not practice deception. Descartes goes on later in his Meditations to buttress his position that what is perceived is reliable.

Cartesian Theory and the Mind/Body Problem

The mind/body problem is also called the problem of dualism. Descartes believed that since the mind is atemporal and aspatial, it is indestructible. Only that which exists in time and is extended in space is destructible. This is why, according to rationalists, reason is innate and everlasting, while knowledge according to the empiricists, is learned over time. Descartes’ position on rationalism formed the foundation for the reliability of science. The emphasis became the scientific rational mind acting on the inert substances of the world. This formed the basis for experimentation.

Ultimately, it is important to remember that Descartes position was epistemological (e.g., based on a theory of knowledge). While his theory was useful, the question becomes apparent that does this idea, the cogito which is useful, really describe reality (e.g., Metaphysics)? This then is the fatal flaw in Descartes’ system. While the cogito is useful epistemologically, is it warranted metaphysically? And if not, then how can one say his system is reasonable at all?

The metaphysical problem with Descartes’ position is known as “The Mind/Body Problem.” How can an aspatial and atemporal mind interface with a spatial and temporal body? To this day, an adequate explanation has not be found to explain this relationship. Descartes himself claimed that the mind interfaces with the body through the Pineal Gland, but he never adequately explained how they interact.

Cartesian Theory and Environmental Degradation

Objectification in science has led to many scientific proofs, but has divorced one from a integral relationship with the world. In considering the foreign inert bodies of the world (including animals) as unimportant and only useful, many of the excesses of technology have resulted in environmental degradation. It is hard to find value in something that does not have a mind and thus cannot think, and is not able to make moral judgments, and therefore cannot be a moral entity worthy of protection.


The Rationalists, Discourse on Great Thinkers. Doubleday 1974.

Honderich, Ted. Ed., The Oxford Companion to Philosophy. Oxford: Oxford University Press, 1995.

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Doug Frame

I am a former professor who taught for almost 10 years. I have a BA and an MA in Philosophy. I enjoy writing about philosophy but ever more so I enjoy writing philosophy.

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