PHILOSOPHY OF RENE DESCARTES

Intro: By drawing a distinction between the mind and the body, and prioritising reason over observation, Rene Descartes laid the foundations for modern rationalist philosophy

Cartesian Dualism

DESCARTES regarded the ability to reason as the defining feature of human beings. He believed that we have this ability because we possess a mind, or soul, which he saw as distinct from the physical body. He distinguished the mind from the body while engaged in his “method of doubt”, which was his unique method of philosophical enquiry.

This method of doubt was a sceptical approach, and led Descartes to conclude that our senses are far from reliable. Truth, he decided, can only be arrived at through reason. His claim “Cogito ergo sum” (“I am thinking, therefore I exist”) expressed his realisation that the only thing that he could be certain of was that he existed – that in order to think at all, he must exist. In addition, he realised that he was a thing that thinks – but not a physical thing, for he could doubt that his physical body was real. He concluded that there were two distinct parts of his existence – an unthinking physical body, and a thinking, non-physical mind.

This led Descartes to conclude that there are two different types of substance – one material and one immaterial – in the universe. This view became known as Cartesian dualism. It raised the question of how the two substances interact, which is still debated today. Descartes claimed that mind and body “commingle” in the pineal gland of the brain, but he failed to show how they do so, and for many, including Thomas Hobbes, this failure undermined Descartes’ theory.

In Descartes’ day, sophisticated machines were being constructed – some even behaved like living things – and scientists believed that the world was mechanical, too: animals, the weather, and the stars were seen as machines whose movements could in principle be predicted. Descartes shared this view about everything except human beings: he claimed that we alone have the God-given attribute of reason.

The Pineal Gland

Descartes believed that the mind and the body are two distinct entities, but conceded that there had to be some interaction between the two. In particular, he thought that the mind exercises control over the body. Indeed, our rational freedom – our ability to choose how to act – is a definingly human characteristic.

However, there must be a place where our minds interact with our bodies. Descartes suggested this is the pineal gland, which is located in the centre of the brain. He described it as “the principal seat of the soul, and the place in which all our thoughts are formed”.

Need To Know

. An influential mathematician as well as philosopher, Descartes invented the system of Cartesian coordinates and established the field of analytical geometry.

In a letter to Mersenne (1640) Descartes wrote: “With me, everything turns into mathematics.”

. According to Descartes, the mind, or soul, is unique to human beings. Other animals are purely physical beings, and behave in predetermined ways.

. Descartes’ mind/body dualism is regarded as the foundation of modern Western philosophy. However, in the 19th and 20th centuries, materialism increasingly became the norm.

Mind And Soul

For Descartes, the mind is the immaterial part of our being – the thinking thing that has the ability to have ideas. It is not located in space, and can doubt everything that it perceives – even the reality of the eyes through which it sees.

Because the mind is immaterial, it is not subject to physical decay. It is therefore eternal, and synonymous with the immortal soul or spirit. For Descartes, dualism was compatible with religious faith.

The Immaterial and Material World

Descartes defined the immaterial world as being the world of ideas, thoughts, and the spirit. It is composed of an immaterial substance that cannot be experienced by the senses, but which we have access to through reason, or rational thought.

Conversely, the physical world is composed of a material substance, which we experience with our senses. It is unthinking and mechanistic, and is governed by the laws of physics. Our physical bodies consist of a material substance, and without our immaterial minds we would simply be unthinking machines.

Two Worlds

Descartes accepted the prevailing scientific view that all material things are mechanical. However, he believed that the immaterial mind is a uniquely human, God-given attribute, and that its ability to reason enables us to gain knowledge of immaterial things such as God, mathematics, and various physical laws.

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THE BODY AS A MACHINE

THE mind/body dualism of Rene Descartes sparked a debate through the 17th and 18th centuries. The question of how two substances (material and immaterial) interact is still debated and researched today. But foremost among those who rejected Descartes’ theory was a British philosopher, Thomas Hobbes.

Physicalism

Hobbes (1588–1679) was a contemporary of Descartes’, and closely corresponded with him about mathematics. However, he differed from Descartes about dualism. He did not accept Descartes’ idea of an immaterial substance, which he considered a contradiction in terms: a substance by its nature must be material. Following that belief, he argued that if there are no immaterial substances then everything must be material – a view that has since become known as physicalism.

Hobbes took a particular interest in the natural sciences and was influenced by the ideas of Galileo. Like many other thinkers of the time, he thought the universe behaves like a machine, and so is subject to physical laws. The movements of the planets and other heavenly bodies are explained by these laws, which apply to all physical objects. If, as Hobbes believed, humans are purely physical, then we too follow the same laws, and are effectively biological machines. Even our minds, Hobbes argued, are physical: our thoughts and intentions are not evidence of some immaterial substance, but the result of physical processes in our brains.

Hobbes’s concept of a purely physical universe was a radical departure from conventional thinking at the time, especially since it denied the existence of an immaterial God. However, it provided a counterargument to rationalism and paved the way for a distinctively British empiricist approach to philosophy.

Mind-Brain Identity

Hobbes did not distinguish between the substances of mind and body: he argued that there is only physical substance, so the mind and the brain are one and the same thing. This means, in effect, that the thoughts and feelings that we experience are physical events in the brain, which are prompted by information provided by our senses. These thoughts and feelings are not made of some form of immaterial substance, but can be understood in terms of physical processes. This idea was reformulated in the 20th century as the mind-brain identity theory.  

Cogs in the machine

For Hobbes, physical laws govern the universe, which is made of many component parts, each of which has its own function, and is governed by physical laws.

The natural world forms one such part of the universe, and within it plants, animals, and humans each play their part. Humans have organised themselves into societies, and these in turn are governed by laws.

Biologically, each human being is a complex machine, composed of numerous functioning parts, all of which are controlled by physical processes within the brain. The brain itself, according to Hobbes, is controlled by internal and external stimuli.

Hobbes’ Theory – In Summary

The body

Our bodies are biological machines and are governed by physical laws. We have physical needs, which prompt “vital” movements, such as the beating of our hearts. However, even our most “voluntary” movements are physically predetermined.

Society

Hobbes believed that humans are selfish and exist only to satisfy their individual physical needs. To avoid chaos, we organise ourselves into societies and submit to the rule of law, which serves as a kind of personal protection agency.

Nature

The universe is purely physical, according to Hobbes, and operates like clockwork according to natural laws of motion. The natural world we live in is a part of that universe, and it and its component parts are similarly machine-like. Everything is predetermined, leaving no room for free will, nor for the mind as anything other than the operation of the brain.