Rene Descartes and Dualism

Biography: Rene Descartes was born in La Haye, France (the town was renamed Descartes in his honor in 1967). Many of the men in his family, including his father, were lawyers and they expected him to follow in that tradition. He attended the college at La Fleche where he received a classical education although his teachers were aware of the new scientific discoveries. While Descartes was a student his teachers celebrated the first anniversary of Galileo’s discovery of the moons of Jupiter. Nevertheless, the physics taught at La Fleche remained thoroughly Aristotelian. Descartes attended the University of Poitiers where he received a degree in law. After graduation, he served briefly as a soldier, most likely as a military engineer. During that time he met the Dutch mathematician Isaac Beeckman who encouraged Descartes’s interest in mathematics. One of the products of that meeting was Descartes’s elucidation of the basic principles of analytic geometry.

One night, while he was still a soldier, Descartes had three vivid dreams. When he awoke he realized that he had a new mission in life: to completely revise how knowledge was acquired. He began with natural philosophy (physics), a project that took many years. Eventually, he moved to the Netherlands where he spent the longest portion of his life and did the majority of his writing. He withheld publication of his ambitious project titled, The World, after he heard of Galileo’s condemnation by the Inquisition. In that never published work Descartes placed Copernicus’s theory of a moving earth front and center.


Contributions: In 1637 Descartes published his Discourse on the Method. In it he outlined the basics of his new system for seeking knowledge and appended three other important works: Optics, Meteorology, and Geometry; those provided concrete examples of his scientific research. In his research on optics, Descartes explained the phenomenon of refraction. Descartes would later use this phenomenon to explain his approach to the proper methods for gathering knowledge. Central to his later thinking was the fact that the immersed object only looked broken; the information presented by the senses was false. However, the mathematically derived rules explaining the phenomenon were true. Physics, Descartes realized, needed a firm metaphysical foundation in order to explain discordant results such as those.


In his Meditations, Descartes moved into metaphysics and in the process helped found the new philosophy. Recall that metaphysics is the study of first principles and of how knowledge is acquired. Descartes’s first step was to decide whether he knew anything at all. He began by doubting everything and by positing that the human mind was an imperfect and limited version of God’s mind. That latter conjecture allowed him to assume the existence of a benevolent God, one who would not intentionally deceive him. He required that step in order, “to reinstate his belief in the world around him” (Cottingham, 1992, p. 8). The breakthrough for Descartes came when he realized that he himself was thinking, and declared “Cogito, ergo sum.” Or, “I think, therefore I am.” He had finally found the bottom, the bedrock foundation of his knowledge. He did exist. From that new secure foundation he could safely and successfully construct his new system of knowledge.


Descartes then moved on to divide the world into two parts. The external, physical part was composed only of matter, and no longer possessed Aristotle’s ten qualities which meant that physicists could now legitimately study matter mechanistically by measuring its size, shape, position, and motion. Descartes realized that traditional followers of Aristotle’s physics would object and ignore his new approach, so he continued to avoid publishing about controversial topics such as Copernicus’s heliocentric model. He was extremely conscious of the danger of being branded a heretic, or worse, an atheist, charges that could be leveled as easily by Catholics or Protestants. The other part of the world was mind. To Descartes, the human mind was not material. Instead, it was an internal, immaterial, and independent entity. The mind could think, imagine, and sense. It operated on ideas and possessed a will that allowed it to seek pleasure or avoid pain. Descartes had defined one of the most persistent of all modern philosophical questions, the mind-body problem.


The Mind-Body Problem: Descartes’s division of the world into body and mind was revolutionary. Physics now could concentrate on the body half and only concern itself with the material parts of the universe. Furthermore, mathematics could explain the workings of the universe beyond all doubt using only the minimum of measurable variables: the size, shape, position, and motion of objects. The mind was where variables such as color, sounds, smells, and tastes originated. Those variables were highly individualized and could not be explained with the same mathematical precision and rigor. In time, many philosophers would refer to size, shape, position, and speed as primary qualities and to color, smells, and tastes as secondary qualities. Descartes was left with the problem of explaining how body and mind interacted.

Descartes’s solution to the mind-body problem is called interactionism, a type of dualism. He believed that both body and mind existed and that each affected the other. In his Discourse on methods and meditations, he wrote (Descartes, (1912/1637, p. 139):


"I here remark, in the first place, that there is a vast difference between mind and body, in respect that body, from its nature, is always divisible, and that mind is entirely indivisible. For in truth, when I consider the mind, that is, when I consider myself in so far only I am a thinking thing, I can distinguish in myself no parts, but I very clearly discern that I am somewhat absolutely one and entire; and although the whole mind seems to be united to the whole body, yet, when a foot, or an arm, or any other part, is cut off, I am conscious that nothing has been taken away from my mind;"


The mechanism behind Descartes’s interactive dualism was hard to explain. How could an immaterial mind affect a material body and vice versa? Descartes struggled to explain the relationship to his critics but was never completely successful. He claimed that the pineal gland of the brain was the locus where his interactionism occurred. But, his explanations involving animal spirits moving through hollow tubes (e.g., nerves), soon proved inadequate. His theory, was inspired by the moving statues at the royal gardens at St. Germain; they moved because of water pumped in or out of tubes. To explain reflexes mechanistically in both humans and animals he believed that nerves, too, were hollow tubes filled with animal spirits, a liquid. So, when an external stimulus such as a fire heated the spirits they pushed on the pineal gland, which in turn sent animal spirits down another nerve tube, moving the affected body part. But, he distinguished between humans and animals by assigning a mind only to humans. Animals, he believed, had no minds and behaved exclusively as the result of mechanistic principles. Nearly all of the details of Descartes’s physics failed to stand the test of time. For example, Newton’s theories of gravitation quickly superseded Descartes vortex theory of planetary and satellite motion (Hetherington, 2006). His mind-body distinction, however, has lasted until the present day. Later philosophers have proposed other solutions to the mind-body problem, including the monistic solutions (e.g., either mind or body) of idealism and materialism and the dualistic solutions (e.g., mind and body) of epiphenomenalism, occasionalism, parallelism, double aspectism, and pre-established harmony.

Descartes’s Later Life and Legacy: The necessity of nearly constantly defending himself and his ideas eventually led to Descartes leaving the Netherlands. He reluctantly accepted an offer from Queen Christina of Sweden to serve in her court. One reason for his hesitancy was that Sweden was a Protestant country (Descartes remained a lifelong Catholic.). After arriving there, things got worse. For one, he was used to spending mornings in bed. Queen Christina, however, ordered him to give her lessons in philosophy at 5 a.m. In the cold morning air Descartes soon took sick, worsened, and died of pneumonia. He was first buried in Stockholm but later reburied in Paris in the Abbey of St. Germain-des-Pres.


Descartes’s legacy in philosophy was vast. Not only was he the founder of the new philosophy, he also inspired other philosophers to complete and refine his rationalist approach to philosophy or create new philosophies to counter it. Another measure of Descartes’s legacy was the fact that the Catholic Church placed all of his books on the Index, the list of prohibited works, in 1633 where they remained until the Index itself was abolished in 1966. Descartes’s discovery of analytical geometry, alone, would have made him a historically prominent mathematician. Descartes himself, however, might have considered his physics his greatest legacy for it was his greatest passion. It is ironic that physics was where his ideas lasted the least amount of time.

Interactionism-the belief that there exists a separation between the physical world and the mental world and that each can affect the other.

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