The World (Descartes)

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Descartes' Le Monde, 1664 Descartes - Le Monde, 1664.jpg
Descartes' Le Monde, 1664

The World, also called Treatise on the Light (French title: Traité du monde et de la lumière), is a book by René Descartes (15961650). Written between 1629 and 1633, it contains a nearly complete version of his philosophy, from method, to metaphysics, to physics and biology.

French language Romance language

French is a Romance language of the Indo-European family. It descended from the Vulgar Latin of the Roman Empire, as did all Romance languages. French evolved from Gallo-Romance, the spoken Latin in Gaul, and more specifically in Northern Gaul. Its closest relatives are the other langues d'oïl—languages historically spoken in northern France and in southern Belgium, which French (Francien) has largely supplanted. French was also influenced by native Celtic languages of Northern Roman Gaul like Gallia Belgica and by the (Germanic) Frankish language of the post-Roman Frankish invaders. Today, owing to France's past overseas expansion, there are numerous French-based creole languages, most notably Haitian Creole. A French-speaking person or nation may be referred to as Francophone in both English and French.

René Descartes 17th-century French philosopher, mathematician, and scientist

René Descartes was a French philosopher, mathematician, and scientist. A native of the Kingdom of France, he spent about 20 years (1629–1649) of his life in the Dutch Republic after serving for a while in the Dutch States Army of Maurice of Nassau, Prince of Orange and the Stadtholder of the United Provinces. He is generally considered one of the most notable intellectual figures of the Dutch Golden Age.

Philosophy intellectual and/or logical study of general and fundamental problems

Philosophy is the study of general and fundamental questions about existence, knowledge, values, reason, mind, and language. Such questions are often posed as problems to be studied or resolved. The term was probably coined by Pythagoras. Philosophical methods include questioning, critical discussion, rational argument, and systematic presentation. Classic philosophical questions include: Is it possible to know anything and to prove it? What is most real? Philosophers also pose more practical and concrete questions such as: Is there a best way to live? Is it better to be just or unjust? Do humans have free will?


Descartes espoused mechanical philosophy, a form of natural philosophy popular in the 17th century. He thought everything physical in the universe to be made of tiny "corpuscles" of matter. Corpuscularianism is closely related to atomism. The main difference was that Descartes maintained that there could be no vacuum, and all matter was constantly swirling to prevent a void as corpuscles moved through other matter. The World presents a corpuscularian cosmology in which swirling vortices explain, among other phenomena, the creation of the Solar System and the circular motion of planets around the Sun.

Mechanism is the belief that natural wholes are like complicated machines or artifacts, composed of parts lacking any intrinsic relationship to each other. Thus, the source of an apparent thing's activities is not the whole itself, but its parts or an external influence on the parts.

Natural philosophy ancient philosophical study of nature and physical universe that was dominant before the development of modern science. It is considered to be the precursor of natural science

Natural philosophy or philosophy of nature was the philosophical study of nature and the physical universe that was dominant before the development of modern science. It is considered to be the precursor of natural science.

Corpuscularianism is a physical theory that supposes all matter to be composed of minute particles. The theory became important in the seventeenth century; amongst the leading corpuscularians were Thomas Hobbes, René Descartes, Pierre Gassendi, Robert Boyle, Isaac Newton, and John Locke.

The World rests on the heliocentric view, first explicated in Western Europe by Copernicus. Descartes delayed the book's release upon news of the Roman Inquisition's conviction of Galileo for "suspicion of heresy" and sentencing to house arrest. Descartes discussed his work on the book, and his decision not to release it, in letters with another philosopher, Marin Mersenne. [1]

The Roman Inquisition, formally the Supreme Sacred Congregation of the Roman and Universal Inquisition, was a system of tribunals developed by the Holy See of the Roman Catholic Church, during the second half of the 16th century, responsible for prosecuting individuals accused of a wide array of crimes relating to religious doctrine or alternate religious doctrine or alternate religious beliefs. In the period after the Medieval Inquisition, it was one of three different manifestations of the wider Catholic Inquisition along with the Spanish Inquisition and Portuguese Inquisition.

Marin Mersenne French theologian, philosopher, mathematician and music theorist, often referred to as the "father of acoustics"

Marin Mersenne, Marin Mersennus or le PèreMersenne was a French polymath, whose works touched a wide variety of fields. He is perhaps best known today among mathematicians for Mersenne prime numbers, those which can be written in the form Mn = 2n − 1 for some integer n. He also developed Mersenne's laws, which describe the harmonics of a vibrating string, and his seminal work on music theory, Harmonie universelle, for which he is referred to as the "father of acoustics". Mersenne, an ordained priest, had many contacts in the scientific world and has been called "the center of the world of science and mathematics during the first half of the 1600s" and, because of his ability to make connections between people and ideas, "the post-box of Europe". He was also a member of the Minim religious order and wrote and lectured on theology and philosophy.

Some material from The World was revised for publication as Principia philosophiae or Principles of Philosophy (1644), a Latin textbook at first intended by Descartes to replace the Aristotelian textbooks then used in universities. In the Principles the heliocentric tone was softened slightly with a relativist frame of reference. The last chapter of The World was published separately as De Homine (On Man) in 1662. The rest of The World was finally published in 1664, and the entire text in 1677.

<i>Principles of Philosophy</i> book by Descartes

Principles of Philosophy is a book by René Descartes. In essence it is a synthesis of the Discourse on Method and Meditations on First Philosophy It was written in Latin, published in 1644 and dedicated to Elisabeth of Bohemia, with whom Descartes had a long-standing friendship. A French version followed in 1647. It set forth the principles of nature—the Laws of Physics—as Descartes viewed them. Most notably, it set forth the principle that in the absence of external forces, an object's motion will be uniform and in a straight line. Newton borrowed this principle from Descartes and included it in his own Principia; to this day, it is still generally referred to as Newton's First Law of Motion. The book was primarily intended to replace the Aristotelian curriculum then used in French and British universities. The work provides a systematic statement of his metaphysics and natural philosophy, and represents the first truly comprehensive, mechanistic account of the universe.

The void and particles in nature

Before Descartes begins to describe his theories in physics, he introduces the reader to the idea that there is no relationship between our sensations and what creates these sensations, thereby casting doubt on the Aristotelian belief that such a relationship existed. Next he describes how fire is capable of breaking wood apart into its minuscule parts through the rapid motion of the particles of fire within the flames. This rapid motion of particles is what gives fire its heat, since Descartes claims heat is nothing more than just the motion of particles, and what causes it to produce light.

According to Descartes, the motion, or agitation, of these particles is what gives substances their properties (i.e. their fluidity and hardness). Fire is the most fluid and has enough energy to render most other bodies fluid whereas the particles of air lack the force necessary to do the same. Hard bodies have particles that are all equally hard to separate from the whole.

Based on his observations of how resistant nature is to a vacuum, Descartes deduced that all particles in nature are packed together such that there is no void or empty space in nature (however, Descartes makes it clear that he does not claim that a void cannot exist in nature, since he lacks the observations necessary to say this with certainty).

Descartes describes substances as consisting only of three elementary elements: fire, air and earth, from which the properties of any substance can be characterized by its composition of these elements, the size and arrangement of the particles in the substance, and the motion of its particles.

Cartesian laws of motion

The motion of these particles and all other objects in nature are subject to the laws of motion Descartes had observed:

  1. “…each particular part of matter always continues in the same state unless collision with others forces it to change its state.”
  2. “…when one of these bodies pushes another, it cannot give the 2nd any motion, except by losing as much of its own motion at the same time…”
  3. “…when a body is moving…each of its parts individually tends always to continue moving along a straight line” (Gaukroger)

Descartes in Principles of Philosophy added to these his laws on elastic collision. [2]

Elastic collision Collision between two objects where conservation of energy and momentum hold true

An elastic collision is an encounter between two bodies in which the total kinetic energy of the two bodies remains the same. In an ideal, perfectly elastic collision, there is no net conversion of kinetic energy into other forms such as heat, noise, or potential energy.

The Cartesian universe

Descartes elaborates on how the universe could have started from utter chaos and with these basic laws could have had its particles arranged so as to resemble the universe we observe today. Once the particles in the chaotic universe began to move, the overall motion would have been circular because there is no void in nature, so whenever a single particle moves, another particle must also move to occupy the space where the previous particle once was. This type of circular motion, or vortex, would have created what Descartes observed to be the orbits of the planets about the sun with the heavier objects spinning out towards the outside of the vortex and the lighter objects remaining closer to the center. To explain this, Descartes used the analogy of a river that carried both floating debris (leaves, feathers, etc.) and heavy boats. If the river abruptly arrived at a sharp bend, the boats would follow Descartes third law of motion and hit the shore of the river since the flow of the particles in the river would not have enough force to change the direction of the boat. However, the much lighter floating debris would follow the river since the particles in the river would have sufficient force to change the direction of the debris. In the heavens, it’s the circular flow of celestial particles, or aether, that causes the motion of the planets to be circular.

As to the reason why heavy objects on Earth fall, Descartes explained this through the agitation of the particles in the atmosphere. The particles of the aether have greater agitation than the particles of air, which in turn have greater agitation than the particles that compose terrestrial objects (e.g. stones). The greater agitation of the aether prevents the particles of air from escaping into the heavens, just as the agitation of air particles forces terrestrial bodies, whose particles have far less agitation than those of air, to descend towards the world.

Cartesian theory on light

With his laws of motion set forth and the universe operating under these laws, Descartes next begins to describe his theory on the nature of light. Descartes believed that light traveled instantaneously - a common belief at the time – as an impulse across all the adjacent particles in nature, since Descartes believed nature was without a void. To illustrate this, Descartes used the example of a stick being pushed against some body. Just as the force which is felt at one end of the stick is instantly transferred and felt at the other end, so is the impulse of light that is sent across the heavens and through the atmosphere from luminous bodies to our eyes. Descartes attributed light to have 12 distinct properties:

  1. Light extends circularly in all direction from luminous bodies
  2. Light extends out to any distance
  3. Light travels instantaneously
  4. Light travels ordinarily in straight lines or rays
  5. Several rays can come from different points and meet at the same point
  6. Several rays can start at the same point and travel in different directions
  7. Several rays can pass through the same point without impeding each other
  8. If the rays are of very unequal force, then they can sometimes impede one another


Contents of The World

  1. On the Difference Between our Sensations and the Things That Produce Them
  2. In What the Heat and Light of Fire Consists
  3. On Hardness and Liquidity
  4. On the Void, and How it Happens that Our Senses Are Not Aware of Certain Bodies
  5. On the Number of Elements and on Their Qualities
  6. Description of a New World, and on the Qualities of the Matter of Which it is Composed
  7. On the Laws of Nature of this New World
  8. On the Formation of the Sun and the Stars of the New World
  9. On the Origin and the Course of the Planets and Comets in General; and of Comets in Particular
  10. On the Planets in General, and in Particular on the Earth and Moon
  11. On Weight
  12. On the Ebb and Flow of the Sea
  13. On Light
  14. On the Properties of Light
  15. That the Face of the Heaven of That New World Must Appear to Its Inhabitants Completely like That of Our World


  1. Gaukroger, Stephen (2004). Descartes an intellectual biography (Repr., paperback ed.). Oxford: Oxford University Press. ISBN   0198237243.
  2. Daniel Garber (2003). The Cambridge history of seventeenth-century philosophy: Volume I. Cambridge University Press. p. 688. ISBN   978-0-521-53720-9 . Retrieved 27 April 2013.

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