Existentialism - By Branch / Doctrine - The Basics of Philosophy
Existentialism is a philosophy that emphasizes individual existence, freedom and choice. It is the view that humans define their own meaning in life, and try to ...
Descartes
Although Sartre is considered by most to be the pre-eminent Existentialist, and by many to be an important and innovative philosopher in his own right, others are much less impressed by his contributions. Heidegger himself thought that Sartre had merely taken his own work and regressed it back to the subject-object orientated philosophy of <anchor>Descartes</anchor> and Husserl, which is exactly what Heidegger had been trying to free philosophy from. Some see Maurice Merleau-Ponty (1908 - 1961) as a better Existentialist philosopher, particular for his incorporation of the body as our way of being in the world, and for his more complete analysis of perception (two areas in which Heidegger's work is often seen as deficient).
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# René Descartes

[Introduction](#Introduction) \| [Life](#Life) \| [Work](#Work) \| [Books](#books)

![René Descartes](photos/descartes.jpg)

_René Descartes_

(Portrait by Frans Hals, 1649)

**Introduction**

**René Descartes** (1596 - 1650) was a **French** philosopher, mathematician, scientist and writer of the [Age of Reason](historical_reason.html). He has been called the **"Father of Modern Philosophy"**, and much of subsequent Western philosophy can be seen as a **response** to his writings. He is responsible for one of the **best-known quotations** in philosophy: **_"Cogito, ergo sum"_** ( **"I think, therefore I am"**).

He was a **pioneer** and major figure in 17th Century Continental [Rationalism](movements_rationalism.html) (often known as **Cartesianism**) later advocated by [Baruch Spinoza](philosophers_spinoza.html) and [Gottfried Leibniz](philosophers_leibniz.html), and opposed by the [British Empiricist](movements_british_empiricism.html) school of thought of [Hobbes](philosophers_hobbes.html), [Locke](philosophers_locke.html), [Berkeley](philosophers_berkeley.html) and [Hume](philosophers_hume.html). He represents a **major break** with the [Aristotelianism](movements_aristotelianism.html) and [Scholasticism](movements_scholasticism.html) of the [Medieval](historical_medieval.html) period.

His contribution to **mathematics** was also of the first order, as the inventor of the **Cartesian coordinate system** and the founder of **analytic geometry**, crucial to the invention of **calculus** and **mathematical analysis**. He was also one of the key figures in the **scientific revolution** of the 16th and 17th Centuries.

**Life**

Descartes (pronounced _day-CART_) was **born** in the town of **La Haye en Touraine** (since renamed **Descartes**) in the Loire Valley in central **France** on 31 March 1596. His father, **Joachim Descartes**, was a busy lawyer and magistrate in the **High Court of Justice**, and his mother, **Jeanne (née Brochard)**, died of tuberculosis when René was just one year old. René and his brother and sister, **Pierre** and **Jeanne**, were therefore mainly raised by their **grandmother**.

From 1604 until 1612, he attended the Jesuit **Collège Royal Henry-Le-Grand** at La Flèche, Anjou, studying classics, logic and traditional [Aristotelianism](movements_aristotelianism.html) philosophy. His **health** was poor and he was granted permission to **remain in bed** until 11 o'clock in the morning, a **custom** he maintained for the rest of his life. He then spent some time in **Paris** studying **mathematics**, before studying law at the **University of Poitiers**, in accordance with his **father's wishes** that he should become a **lawyer**, obtaining his **law degree** in 1616.

However, he then **abandoned** his education and spent several years **traveling** and **experiencing the world** (he later claimed that his **formal education** provided little of substance). It was during this time (in 1618) that he met the Dutch philosopher and scientist **Isaac Beeckman** (1588 - 1637) while walking through **Breda** in Holland, who sparked his interest in **mathematics** and the new **physics**.

In 1622, he **returned to France**, and soon afterward **sold all his property** at La Haye, **investing** the proceeds in bonds which provided him with a **comfortable income** for the rest of his life. He returned to settle in **Holland** in 1628. The next year, he joined the **University of Franeker**; the year after that, **Leiden University**; and, in 1635, he is recorded as attending **Utrecht University**. He had a daughter, **Francine**, after a relationship in Amsterdam with a servant girl, **Helène Jans**, although Francine died at the age of five. In fact, in the years between 1628 and 1649, he lived at **14 separate addresses** in 10 different Dutch cities.

It was during this 20 year period of **frequent moves** that he wrote almost all of his **major works** on philosophy, mathematics and science. He shrewdly held off publication of his first work, **_"Le Monde"_** ( **_"The World"_**), written between 1629 and 1633, due to the **condemnation** of the works of **Galileo Galilei** (1564 - 1642) and **Nicolaus Copernicus** (1473 - 1543) by the Roman Catholic Church in 1633. The most famous of his works include: the **_"Discours de la méthode pour bien conduire sa Raison et chercher la Vérité dans les Sciences"_** ( **_"Discourse on the Method"_**) of 1637, his first [rationalist](movements_rationalism.html) vision of the progress of human knowledge; the **_"Meditationes de Prima Philosophia"_** ( **_"Meditations on First Philosophy"_**) of 1641, a more formal exposition of his central tenets, in Latin; and the **_"Principia Philosophiae"_** ( **_"Principles of Philosophy"_**) of 1644, an even more systematic and comprehensive exposition of his views. For a time, in 1643, **Cartesian philosophy** was **condemned** by the University of Utrecht.

Descartes **died of pneumonia** on 11 February 1650 in **Stockholm, Sweden**, where he had been invited as a teacher for **Queen Christina** of Sweden. Later, his remains were taken to **France** and buried in the church of **Sainte-Geneviève-du-Mont** in Paris, and then, during the **French Revolution**, disinterred for burial in the **Panthéon** among the other great thinkers of France. Currently, his tomb is in the church of **Saint-Germain-des-Prés** in Paris, and his brain is in the **Musée de l'Homme**.

**Work**[Back to Top](#Top)

Descartes lived during a very [skeptical](branch_skepticism.html) period, at a time before **science** as we know it existed, and after a long period of relative **stagnation** in philosophical thought during the Church-dominated and [Aristotle](philosophers_aristotle.html)-influenced late [Middle Ages](historical_medieval.html). He had been impressed, in both his academic work and in his experience of the world at large, by the realization that there appeared to be no **certain** way of acquiring **knowledge**, and he saw his main task as the [epistemological](branch_epistemology.html) one of establishing what might be **certain knowledge** as a stepping stone towards the ultimate pursuit of **truth**. His more immediate aim in this was to put **scientific inquiry** in a position where it was no longer subject to attack by [Skeptics](movements_skepticism.html), and he tried to do this by a kind of **pre-emptive** [Skepticism](movements_skepticism.html), essentially by being more [skeptical](branch_skepticism.html) than the [Skeptics](movements_skepticism.html).

At the heart of Descartes' philosophical method was his **refusal to accept** the authority of **previous philosophers**, and even of the evidence of **his own senses**, and to trust only that which was clearly and distinctly seen to be **beyond any doubt** (a process often referred to as **methodological skepticism** or **Cartesian doubt** or **hyperbolic doubt**). Only then did he allow himself to **reconstruct** knowledge (piece by piece, such that at no stage was the **possibility of doubt** allowed to creep back in) in order to acquire a firm foundation for **genuine knowledge** and to dispel any [Skepticism](branch_skepticism.html).

He outlined **four main rules** for himself in his thinking:

- Never accept anything except **clear and distinct ideas**.
- **Divide each problem** into as many parts are **needed** to solve it.
- **Order your thoughts** from the simple to the complex.
- Always **check thoroughly** for oversights.

Using this process, which he detailed in his epochal **_"Discourse on the Method"_** of 1637 and expanded in the **_"Meditations on First Philosophy"_** of 1641, Descartes attempted to narrow down, by what is sometimes called the **method of doubt**, what was **certain** and what contained even a shadow of a doubt. For example, he realized that he could **doubt** even something as apparently fundamental as whether he had a **body** (it could be that he was just **dreaming** of it or that it was an **illusion** created by an **evil demon**), but he could not, under any circumstances, doubt whether he had a **mind** or that he could think. He followed this up with a pure, abstract **thought experiment**. He imagined an evil spirit (or **"deceiving demon"**) whose sole intention was to **mislead** him, and asked whether there was **anything** about which the demon would **not** be able to mislead him. His conclusion was the **act of thinking**, that the demon could never make him believe that he was thinking when he was not (because, after all, even a **false thought** is still a thought).

Having identified this **single indubitable principle**, that **thought exists**, he then argued that, if someone was **wondering** whether or not he existed, then the very act of thinking was, in and of itself, **proof** that he **did** in fact exist: the famous **_"Je pense, donc je suis"_** ("I think, therefore I am") - the similar statement in Latin, **_"Cogito ergo sum"_** is found in his later **_"Principles of Philosophy"_**. It is worth mentioning here that, by "thinking", Descartes did not just mean **conceptual thought**, but all forms of **consciousness**, experience, feelings, etc.

Having dispelled all doubt by this process, Descartes then worked to build up, or **reconstitute**, the world again. But he was careful not to do this willy-nilly, but only according to his own very **strict rules**, so that the "reconstituted world" was not the same as the original one which he had dismantled piece by piece due to doubts. The way he achieved this (which, it must be said, appears from a **modern** viewpoint like something of a **conjuring trick**) was to argue that among the contents of our (certain) consciousness was the idea of **God**, which in itself he saw as proof of the existence of God. He then argued that, if we have the **overwhelming impression** of the existence of a concrete world around us, as we do, then an omnipotent, omniscient and omnibenevolent God would **ensure** that such a world does in fact exist for us. Furthermore, he asserted that the **essence** of this physical world was **extension** (that it takes up space), contrary to the extensionless world of the mind.

Paradoxically, this was an essential step forward in 17th Century **science** as it established a physical world which was of a **mathematical character** and permitted mathematical physics to be used to **explain** it. Also important is that, as we have seen, although God was **indispensable** to Descartes' method of arriving at a physical world, once such a world was **accepted**, it was no longer necessary to involve God in the description and measurement and explanation of how things work. Thus, the **process of science** was freed from **theological constraints** and interference.

Descartes dismissed the **senses** and **perception** as **unreliable**, and to demonstrate this he used the so-called **Wax Argument**. This revolves around the idea that a wax object, which has certain **properties** of size, color, smell, temperature, etc, appears to change almost all of these properties when it is melted, to the extent that it appears to our senses to be a **completely different** thing. However, we know that it is in fact still the **same** piece of wax. Descartes concluded from this that the senses can be misleading and that **reason** and **deduction** is the only **reliable** method of attaining knowledge, which is the essence of [Rationalism](branch_rationalism.html).

Descartes further argued that **sensory perceptions** come to him involuntarily (not willed by him), and are therefore **external** to his senses and therefore evidence of the **existence of an external world** outside of his mind. He argued that the things in the external world are **material** because God would not **deceive** him as to the ideas that are being transmitted, and has given him the **propensity to believe** that such ideas are caused by material things. Because of this belief that God is **benevolent** and does not desire to deceive him, he can therefore have some **faith** in the account of reality his **senses** provide him.

Descartes believed that the **human body** works like a **machine**, that it has the material properties of **extension** and **motion**, and that it follows the **laws of physics**. The pieces of the human machine, he argued, are like **clockwork mechanisms**, and that the machine could be understood by **taking its pieces apart**, studying them, and then **putting them back together** to see the larger picture (an idea referred to as [Reductionism](branch_reductionism.html)). The **mind** or **soul**, on the other hand, is a **non-material** entity that **lacks** extension and motion, and **does not follow** the laws of physics.

Descartes was the first to formulate the **mind-body problem** in the form in which it exists today (see the section on [Philosophy of Mind](branch_philosophy_of_mind.html)), and the first to clearly identify the **mind** with **consciousness** and self-awareness, and to distinguish this from the **brain**, which was the physical seat of **intelligence** ( [Dualism](branch_dualism.html)). In his [epistemological](branch_epistemology.html) work in the **_"Discourse on the Method"_**, he had realized that, although he could doubt that he possessed a body, he could not under any circumstances doubt that he possessed a mind, which led him to conclude that the mind and the body were two very **different and separate things**. His particular form of [Dualism](branch_dualism.html) (known as **Cartesian Dualism**) proposed that the **mind controls the body**, but that the body **also influences** the otherwise rational mind (such as when people act out of **passion**) in a kind of **two-way interaction**, which he claimed, without much evidence, occurred in the **pineal gland**. Gilbert Ryle later described this kind of [Dualism](branch_dualism.html) (where mental activity carries on in **parallel** to physical action, but where their means of interaction are **unknown** or, at best, speculative) as the **"ghost in the machine"**. Although his own solution was far from convincing, this kind of Cartesian Dualism set the agenda for philosophical discussion of the **mind-body problem** for many years after Descartes' death.

It should be noted, however, that for all Descartes' innovation and boldness, he does not abandon the traditional **idea of God**. He defined **"substance"** (essentially meaning what the world really consists of) as "that which requires **nothing other than itself** in order to exist", but he concluded that the **only true substance** was God himself, because everything else (from souls to material objects like the human body) was **dependent on God** for its existence. He used his own variations of the **causal argument**, the **ontological argument** and the **cosmological argument** for the existence of God in his **_"Meditations"_** (see the section on [Philosophy of Religion](branch_philosophy_of_religion.html)), and the existence of God played a major role in his **validation** of reason and in **other parts** of Descartes’ system. Given the **important rôle** God plays in his work, suggestions that Descartes was really a closet [atheist](branch_atheism.html), and that he includes the arguments for the existence of God as **window dressing**, appear extremely **unlikely**.

In **mathematics**, Descartes realized that a **graph** could be drawn to show a **geometrical interpretation** of a **mathematical function** using points known as **Cartesian coordinates**, and thereby founded **analytic geometry** or **Cartesian geometry** (using algebra to describe geometry), which was crucial to the subsequent development of **calculus** by **Sir Isaac Newton** (1643 - 1727) and [Gottfried Leibniz](philosophers_leibniz.html). He also invented the notation which uses **superscripts** to indicate powers or **exponents**, and his **rule of signs** is also a commonly used method to determine the number of positive and negative zeros of a **polynomial**. It can be argued that his reflections on **mind and mechanism**, impelled by the invention of the **electronic computer** and by the possibility of **machine intelligence**, blossomed into the **Turing test** of a machine's **capability** to demonstrate **intelligence**.

In **optics**, he showed by using geometric construction and the **law of refraction** (also known as **Descartes' law**) that the angular radius of a **rainbow** is 42 degrees. He also independently discovered the **law of reflection** (that the angle of incidence equals the angle of reflection).

In **physics**, Descartes introduced (before Newton) the concept of **momentum** of a moving body (what he termed the "amount of motion"), which he defined as the product of the **mass** of the body and its **velocity** or speed. His three **"laws of nature"** became the basis of Newton's later **laws of motion** and the modern theory of **dynamics**: that each thing tries to remain in the **same state** and, once moved, **continues** to move; that all movement is along **straight lines**; and that when a body comes into contact with another body the **combined** "quantity of motion" remain the **same** (his **conservation of motion** principle).

In an attempt to explain the **orbits of planets**, Descartes also constructed his **vortex theory** which would become the most popular **theory of planetary motion** of the late 17th Century (although subsequently discredited). However, he continued to cling to the traditional **mechanical philosophy** of the 17th Century, which held that everything physical in the universe to be made of tiny **"corpuscles"** of matter (although, unlike [Atomism](branch_atomism.html), the theory maintained that there could be **no vacuum**, just a mass of swirling matter).

**René Descartes Books**[Back to Top](#Top)

See the additional sources and recommended reading list below, or check the [philosophy books](philosophy-books.html) page for a full list. Whenever possible, I linked to books with my amazon affiliate code, and as an Amazon Associate I earn from qualifying purchases. Purchasing from these links helps to keep the website running, and I am grateful for your support!

- [Oeuvres De Descartes](https://amzn.to/2I19J4H)

  by Rene. Adam, Charles, & Tannery, Paul, Ed. Descartes (Author)

- [The Philosophical Works of Descartes (v. 1)](https://amzn.to/2FiKWWQ)


  by René Descartes (Author), Elizabeth S. Haldane (Translator), G. R. T. Ross (Translator)

- [The Philosophical Writings of Descartes (Volume 3: The Correspondence (Paperback))](https://amzn.to/2K9AHb4)

  by René Descartes (Author), John Cottingham (Editor), Dugald Murdoch (Editor), Robert Stoothoff (Editor), Anthony Kenny (Editor)

- [Discourse on Method and Meditations on First Philosophy, 4th Ed. 4th Edition](https://amzn.to/2qZ8ryW)

  by Rene Descartes (Author), Donald A. Cress (Translator)

- [The Philosophical Writings of Descartes: Volume 1](https://amzn.to/2HXi89q)

  by René Descartes (Author), John Cottingham (Translator), Robert Stoothoff (Translator), Dugald Murdoch (Translator)

- [Philosophical Essays and Correspondence (Descartes) (Hackett Publishing Co.)](https://amzn.to/2HomuJD)

  by Rene Descartes (Author), Roger Ariew (Author)

- [Descartes: The World and Other Writings (Cambridge Texts in the History of Philosophy)](https://amzn.to/2qV44WI)

  by René Descartes (Author), Stephen Gaukroger (Editor)

- [Discours de la méthode (French Edition) (French) Paperback](https://amzn.to/2HnX6na)

  by René Descartes (Author)

- [Meditations on First Philosophy / Meditationes de prima philosophia: A Bilingual Edition (English and Latin Edition)](https://amzn.to/2qTsb86)

  by Rene Descartes (Author), George Heffernan (Editor)

- [Cogito, Ergo Sum: The Life of Rene Descartes by Richard Watson (2002-04-30) Hardcover – 1884](https://amzn.to/2HJ5A7N)

  by Richard Watson (Author)

- [The Cambridge Companion to Descartes (Cambridge Companions to Philosophy)](https://amzn.to/2HpfFTT)

  by John Cottingham (Editor)

- [Descartes (Hackett Publishing) Reprint Edition](https://amzn.to/2Ho4nPR)

  by Marjorie Glicksman Grene (Author)

- [Descartes: A Study Of His Philosophy (Key Texts) 1st Edition](https://amzn.to/2qTUnaK)

  by Anthony Kenny (Author)

- [Ideas and Mechanism by Margaret Dauler Wilson (1999-02-08)](https://amzn.to/2HUYyKU)

  by Margaret Dauler Wilson (Author)

- [Feminist Interpretations of René Descartes (Re-Reading the Canon) 1st Edition](https://amzn.to/2HoBd7x)

  by Susan Bordo (Editor)

- [Descartes: The Great Philosophers (The Great Philosophers Series) by John Cottingham (1999-07-16)](https://amzn.to/2qYPz3n)

  by John Cottingham (Author)

- [Descartes: An Analytical and Historical Introduction 2nd Edition](https://amzn.to/2FdsjU8)

  by Georges Dicker (Author)

- [Descartes and Method: A Search for a Method in Meditations (Routledge Studies in Seventeenth Century Philosophy) by Clarence A. Bonnen (1999-07-08) Hardcover – 1750](https://amzn.to/2K7wIvz)

  by Clarence A. Bonnen;Daniel E. Flage (Author)

- [Descartes Embodied: Reading Cartesian Philosophy through Cartesian Science](https://amzn.to/2r0PM6e)

  by Daniel Garber (Author)

- [Descartes's Metaphysical Reasoning (Studies in Philosophy) 1st Edition](https://amzn.to/2KcPP7N)

  by Roger Florka (Author)

- [Descartes' Philosophy Interpreted According to the Order of Reasons: The Soul and God \[and\] The Soul and the Body (Volumes I & II) Hardcover – 1984](https://amzn.to/2qUopex)

  by Martial Gueroult (Author), Roger Ariew (Translator)

- [Descartes Against the Skeptics Hardcover – May 18, 1978](https://amzn.to/2qVO0Uo)

  by E. M. Curley (Author)

- [Descartes: Belief, Scepticism and Virtue (Routledge Studies in Seventeenth Century Philosophy) by Richard Davies (2001-05-24) Hardcover – 1644](https://amzn.to/2HPaYXi)

  by Richard Davies (Author)

- [Descartes's Method of Doubt Paperback](https://amzn.to/2HYguV9)

  by Janet Broughton (Author)

- [Descartes' System of Natural Philosophy 1st Edition](https://amzn.to/2qQsoJh)

  by Stephen Gaukroger (Author)

- [Descartes' Natural Philosophy (Routledge Studies in Seventeenth-Century Philosophy) 1st](https://amzn.to/2HWcMLD)

  by S. Gaukroger (Editor), John Schuster (Editor), John Sutton (Editor)

- [Descartes' Metaphysical Physics (Science and Its Conceptual Foundations series) by Daniel Garber (1992-05-01) Paperback](https://amzn.to/2Ho1l25)

  by Daniel Garber (Author)

- [What Am I?: Descartes and the Mind-Body Problem](https://amzn.to/2HqKrjH)

  by Joseph Almog (Author)


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