Cartesian Dualism

Descartes’ Dualism and the Problem of the Bridge

Dualism, simply put, is the belief that something is composed of two fundamentally different components. Descartes believed that a human person consisted of:

Matter/Body: The physical stuff that walks, talks, and lives a life.

Mind: The non-physical substance (sometimes equated with the soul) that thinks, doubts, and remembers things.

He introduced a division between mind and body in order to refute scepticism, using the method of universal doubt.

Descartes believed in a mechanistic view of the material world—that matter goes about its business and follows its own laws, except when it is interfered with by the mind. Human mind, then, simply makes the body act (like a machine). Exactly how the non-physical mind interacts with the physical body is a point of contention. Descartes believed that the pineal gland in the brain was the locus of interaction between the mind and body because he believed that this gland was the only part of the brain that wasn’t a duplicate.

It’s important to remember that, for Descartes, the brain and the mind are not the same thing. The brain serves, in part, as a connection between the mind and the body, but because it is a physical, changeable thing, it is not the actual mind. Our mind is whole and indivisible, whereas our body can be changed. You can cut your hair, remove your appendix, or even lose a limb, but that loss in no way reduces your mind.

Descartes also believed that human were the only dualistic creatures. He placed animals in the realm of the purely physical, mechanistic world, acting purely on instinct and on the laws of nature.

Descartes was led to his dualistic theories in part from his most famous philosophical endeavour—to place into doubt all that could be doubted in the hope of arriving at a basic, undeniable truth. That resulted in his famous Cogito ergo sum—I think, therefore I am. Descartes could doubt the existence of the physical world and that even his own body actually existed, but he could not doubt the idea that his mind existed because doubting is a thought process. The very act of doubting one’s existence proves that one actually exists; otherwise, who is doing the doubting?

Through his process of doubting, he recognized that, regardless of what the changeable physical world was really like, his mind was still whole and unchanged, and therefore somehow separate from that physical world.

For Descartes, mind has evident awareness of all its actions. This he calls the perfect transparency of the mind. A thought, for him, in the wide sense is defined as that of which I am immediately aware. He also analysed the content of his mind and discovered it contained certain innate ideas such as self, God, and substance.

Clear and Distinct Ideas

Descartes claimed that one cannot derive the idea of substance from observation precisely because perception can only generate qualities. Hence he had to posit the idea of substance as an innate idea. Such ideas are called innate because they have been implanted in us before our birth.

Moreover, clarity and distinctness are the marks of truth, the distinguishing characteristics by which we can tell the true from the false. Hence whatever is clearly and distinctly conceived is true. An experience or thought is clear and distinct if it is so forceful that we cannot avoid being aware of it.

As regards ideas that are not clear or distinct, we have no guarantee that what we believe is true. The faculty of judgement functions reliably in relation to the clear and distinct ideas that God has implanted in us. We make mistakes when we misuse our faculties. But we cannot make mistakes when we use them as God intends us to do.

The human mind can achieve systematic and certain knowledge by starting with knowing what is self-evident. God wanted us to direct our thoughts in an orderly manner, beginning with the simplest and most easily known objects and ascend little by little, step by step, to knowledge of the most complex.

Cogito Ergo Sum

Descartes held that I can be absolutely certain only of me as a mental substance that thinks. I have a clear and distinct idea about it.

According to him, even in our sleep we can observe that it is because of our thinking that we exist. We may dismiss the many things that come into our mind as dreams or illusions, but one thing is sure and necessary is that I whom am thinking is something. Without my existence, I cannot think. Therefore, observing this truth, we can say: “I am thinking, therefore I exist.” Descartes decided that he could accept this statement without scruple as the first principle of the philosophy that he was seeking.

Descartes finally concluded that the proposition, I am/I exist is necessarily true whenever it is put forward by me or conceived in my mind. I am certain about this because I can clearly and distinctly see or understand what is being said.

Existence of God and World

One of the innate ideas we have is of a perfect being, God. We are merely finite, temporal creatures, and yet we have the idea of a substance that is infinite, eternal, immutable, omniscient and almighty. Descartes concluded that this idea can only be caused by something that possesses these perfections. Hence there must be a God who is perfect has implanted in me the idea of the perfect being. Now Descartes is certain of two truths: that he exists and God exists. He continued to search for further certainties and realized that if God is a perfect being, then He won’t deceive human beings because fraud and deception are imperfections and hence cannot be characteristics of a perfect being. If God is not a deceiver, then a great deal of the information that had earlier been considered suspect can now be considered reliable. All that is needed is to find out what God wants us to believe as true. Since he cannot deceive us we can place complete faith in the knowledge He gives us.

God has given us clear and distinct mathematical ideas like two plus two make four. Since God has forced this belief upon us, and since He cannot be a deceiver it must be true. We have divine guarantee here. “Every clear and distinct conception is certainly something, and therefore cannot come from nothing, but must necessarily come from God who is supremely perfect and cannot be the cause of any error.” Thus he concludes that the entire realm of mathematical knowledge is true.

But mathematical knowledge only gives me truths about concepts in my mind. Is it possible that I can also be certain that there is an external world? We cannot rely on their existence through our senses for they deceive us. However, in general it is quite clear and distinct to us and we have a strong inclination to believe that there is an external world of material bodies. Since the belief in the external world is a natural one, God would be deceiving us unless it is true. As God is not a deceiver there must be an external physical world. The properties that we can safely attribute it are the primary qualities which are clear and distinct; but we cannot know with certainty the indistinct or unclear features of the world, namely secondary qualities.

Critical Appraisal

Descartes’ picture of the world is hopelessly divided into substances that were defined in ways that mutually exclude each other. How could the mental world – a non-spatial, purely spiritual sphere – have any effect on the physical world of crass matter, and vice versa, in this radically dualistic scheme of things? He assigned all perceivable qualities to the mind and left only mathematically measurable quantities to the external world. Descartes replaced the commonsense view of the direct relation between self and the world with a most circuitous route of relating to the world through the mind.