During the seventeenth century, Aristotelian philosophy was replaced with what has been called the mechanical philosophy, a radically new set of principles that guided the construction of theories about the world. What was the basic ontology of the mechanical philosophy? What counted as legitimate explanation under this framework? Who were the major proponents of the mechanical philosophy, and how did they differ in their views? What is the difference between “atomism” and “corpuscularianism,” that is, were all mechanical philosophers atomists?

     The Scientific Revolution was the source of incredible change in ideologies corresponding to natural philosophy. It saw the development of new equipment such as the microscope, telescope, and vacuum pump, allowing an increase in observational potential. It was during this time period that the modern scientific method was developed. Perhaps the most remarkable accomplishment in this period was the complete reworking of the way the universe was believed to work, decreasing and gradually eliminating the seemingly indefatigable influence of Aristotle. This occured mainly through the development of a new philosophy called mechanical philosophy.  Mechanical philosophy, pioneered by many natural philosophers in the seventeenth and eighteenth centuries, contributed greatly to the physics of the time and represents a breaking point between Aristotelian thought and modern natural philosophy.

     A product of the Scientific Revolution, mechanical philosophy was developed in an attempt to drive Aristotelianism out from its dominant place in natural philosophy. In essence, mechanical philosophy asserted that all natural phenomena could be explained by the interactions between tiny, unobservable particles called corpuscles. This belief allowed philosophers to ascribe primary causes of physical phenomena to the interaction of these invisible particles. For a mechanical philosopher, nature was like a clock in that all of its gears had to work together in a purely mechanical way in order to function.  Under this philosophy, occult or hidden properties were, for the most part, discarded in order to make everything intelligible.  The interaction of miniscule particles replaced occult properties as a much more sound argument for the phenomena occuring in the universe.  

     Mechanical philosophy had many proponents and pioneers in the scientific renaissance, one of the most prominent being Rene Descartes.  Descartes is generally considered the founder of mechanical philosophy. In 1618, Descartes journeyed to the Netherlands to visit a schoolteacher and friend named Isaac Beeckman. Beeckman was developing a corpuscular theory in which all physical phenomena could be explained by the size, shape, and interaction of tiny particles.  Beeckman believed that intelligible contact action between these particles was the only mechanism by which the universe could work.  Beeckman eventually called his ideas "physico-mathematics."

     Descartes was very impressed by Beeckman's theory and sought to expand it to all phenomena, not only those that were physical . In his work Discourse on Method in 1637, Descartes wanted to create a system of absolute certainity and attempted to find a proof in what man knows through systematic doubt.  Descartes also built his ideas on a geometrical and mathematical approach to matter. The identifying characteristic of Cartesian philosophy is the construction of a formal system of doubt, that is, a system of questioning all propositions and conclusions by eliminating all assumptions and prior knowledge. Once one has arrived at a certain piece of knowledge that cannot be doubted; that piece of knowledge then becomes the basis for clearing up other doubts. This doubt lies in the reliability of the senses and has come to be called philosophical skepticism. Eventually, Descartes found that only personal existence and thought could be proven, thus forming his famous quote, "I think therefore I am." From this principle, he began reasoning all things back into existence from first principles, starting with God and moving to those things discernable by the senses.  In this way Descartes reasoned a world into existence without any doubt or argument against his reasoning.

     Descartes believed that extension and number were the only clear and distinct properties that matter posessed and that secondary properties such as color were not properties of the matter directly. Descartes also reasoned that these secondary properties were not part of the object itself, instead they where only perceived as such. For example, a red object is not red, it is just perceived as red. Descartes also proposed that the universe contained two substances: res cognitas and res extensa. Res cognitas was the "thinking substance," the essence of the mind with no physical characteristics. Res extensa was the extended substance or the inert matter of the universe. By this reasoning, Descartes proposed that matter and space were equivalent. The res extensa and the res cognitas are the two parts of Cartesian dualism.

     In Descartes' later works such as Le Monde and the Principles of Philosophy, he described that some of his ideas did contain problems. Some of these problems lay in Descartes' matter theory and cosmology.  If matter is an extension, as Descartes asserted, then space and matter must be infinite, which means the universe is infinite. Descartes also asserted that since space is divisible, matter must be infinitely divisible. Also, since all spaces in the universe are filled, voids or empty spaces, including the vaccuum, may not exist and matter is undifferentiated. Descartes also divided the matter of the cosmos into three kinds that are fundamentally the same, but that interact differently to create different phenomena. He related these types of matter to the properties of light and reflection. The first is the emission field that is the sun, the second is the transmission matter that fills the space between the bodies and the sun, and the third is the reflection which are large bodies like the Earth. Descartes proposed that around each heavenly body there is a vortex of the second type of matter and the vortex keeps the planet on a course around the sun just as the sling keeps a rock in orbit around the hand.

     Descartes' theories concerning motion followed from many of his basic principles. When something moved, according to Descartes, it left behind an empty space that must be filled.  This led Descartes to the idea of natural "vortices" that played a part in the motion of all things. Descartes took this idea and applied it to celestial motion, stating that the planets move around the sun like balls in a whirlpool. This vortical motion did not require physical spheres, like Tycho had suggested, nor did it require the complex motive forces  Kepler had previously posited.  Instead, the fluid vortices were the only mechanism needed to explain the motion of the heavenly bodies. The principles and ideas that Descartes put forth in his own version of mechanical philosophy were greatly influential, replacing those of Aristotle.  Descartes' theories that the universe was a "machine" of matter and motion, and that physical reality and perception were fundamentally separate laid down the basis for future mechanical philosophers. 

       While the ideas of Descartes were unquestionably prominent, Pierre Gassendi was another philosopher who helped shape mechanical philosophy in the scientific renaissance. Though he proposed a logical alternative to Cartesian thought, his ideas were not new. Gassendi advocated a more atomistic method as an alternative to Cartesian philosophy.  He composed much of his mechanical philosophy by analyzing various ancient texts and incorporating the ancients' ideas into his own philosophy. Gassendi's philosophy was much more atomistic than Descartes' and proposed that atoms were indivisible and that they moved in a void.  He also asserted that atoms were not created or destroyed and believed that there were no other properties of bodies except size, shape, and matter.  Because of this focus on atomism, Gassendi formed his own mechanical philosophy that diverged from that of Descartes.  Gassendi also held to the traditions of magic and occult properties in stating that we would never completely know all the properties or secrets of the universe given that true causes are not transparent.

      Another mechanical philosopher who contributed greatly to mechanical philosophy in the scientific renaissance was Robert Boyle (1627-1691).  Boyle was very interested in the study of theology until 1651 when he met the American alchemist, George Starkey.  Starkey instructed Boyle in Alchemy and had a profound effect on him.  Boyle went on to study natural philosophy, especially alchemy and was also influenced by the readings of Descartes, Gassendi, and Daniel Sennert. Boyle, in his most famous work, The Skeptical Chemist, argued against the Aristotelian view of the elements.  In another of his works, The Origin of Forms and Qualities, Boyle argued that there were three properties inherent to matter: size, shape, and motion.  This is in contrast to Descartes' philosophy which ascribed only extension and quantity to matter. Furthermore, he believed that there was one universal kind of matter which, by rearranging, caused change.  This is a drastic change from the three types of matter proposed by Descartes.

      Isaac Newton (1642-1727) is also famous due in part to his work in mechanical philosophy.  Newton, using what is now known as Newtonian Synthesis, was able to accurately derive all motion, including Kepler's Laws, from first principles. Newton agreed with Boyle's idea that there are only three properties of matter and also agreed with him on the idea of attractive properties. Newton's most famous work, the Principia, contains many influences from mechanical philosophy. Newton wrote the Principia using only physical and mathematical properties and calculations. He started out by giving mathematical definitions for physical properties and continued with corollaries needed to understand the physics.  Newton then built upon the evidence he had mounted and gave a mathematical proof for his interpretation of the celestial motion of the cosmos. Newton's most widely known success, the theory of universal gravitation, was put forth in the Principia. The support Newton accrued from mechanical philosophers was astounding especially given the extent to which universal gravitation was non-mechanical. Many mechanical philosophers sought to eliminate all occult causes, but Newton's universal gravitation demanded action at a distance.  This idea of action at a distance with a divine influence for motion left no room for the mechanical action of particles as a cause for universal gravitation.   

      Though both atomism and corpuscularianism postulate the existence of tiny particles whose interactions give rise to physical phenomena, the two theories are fundamentally different. Corpuscularianism was a school of thought that believed that these particles could be divided indefinitely, creating a continuity of matter. This idea was utilized in various fields of alchemy (especially by Geber and his emulators), where elemental mercury was thought to be a universal solvent whose corpuscles were capable of penetrating and purifying any metal and producing gold (chrysopoeia). Corpuscularianism was supported by many natural philosophers, such as Robert Boyle and Sir Isaac Newton, the latter having used it in developing his particulate theory of light.  Atomism, in contrast, stated that these corpuscles were not infinitely divisible, but rather existed as indivisible quantums of matter called atoms. Pierre Gassendi showed interest in the idea of atomic theory, but being a Catholic Priest he disliked its necessarily deistic or atheistic conclusions. This conflict between Gassendi's religion and philosophy caused him to seek out an alternative form of atomism.  Gassendi's atomism was much more akin to classical atomism and excluded the atheistic conclusions of the previous version.  This theory was held by the majority of natural philosophers during the Scientific Revolution because it was seen as a better alternative to Aristotelian ideas and was also compatible with christianity and mechanical philosophy. The prevalence of atomism today can be greatly attributed to this movement. 

     The overwhelming acceptance of particulate mechanical theories, whether they were atomistic or corpuscular, was a definite shift from the ideas of Aristotelianism which had dominated earlier centuries.  This long held belief system, which postulated that physical phenomena could be explained by innate characteristics of objects, was promptly replaced by this new mechanical philosophy. Descartes' theories marked the development of the first logically sound alternative to Aristotle's philosophical system. Mechanical philosophy was then accepted and modified by several natural philosophers, such as Gassendi, Boyle, and Newton, each one contributing his own unique perspective. Through the accretion of these amendments, mechanical philosophy slowly became more complex and better able to explain natural phenomena, resulting in the science we know today.  Mechanical philosophy was pioneered by many natural philosophers in the Scientific Renaissance, diverged from the Aristotelian thought of the time and added greatly to the shifts in natural philosophical thought thats occured during the scientific revolution. 

Sources

Dear, chapter 5

Boyle and Descartes handouts

Lawrence Principle, chapter 7 from The Aspiring Adept: Robert Boyle's Alchemical Quest in the reading packet.