HISTORY OF SCIENCE #15: DESCARTES AND THE MECHANICAL PHILOSOPHY
Rene Descartes 1596-1650
- last great "philosopher scientist"
- Descartes' philosophy called Cartesianism
- pioneered mechanistic philosophy
Biography:
- born 1596, Jesuit-trained
- got law degree, University of Poitiers
- 10 November 1619 conceived new method to obtain true knowledge:
- doubt & search for self-evident principles
- Cardinal de Berulle encouraged his work
- died in court of Queen Christina of Sweden
Descartes as Scientist
- more philosopher than scientist
- but paid much attention to experiment
- method: have firm central theory to test by observation and experiment
- made hypothetical model a tool of research
- scientific knowledge incomplete until it explains
- criticized Galileo for being satisfied with mathematical laws
CARTESIAN PHILOSOPHY
- Discours de la Method (1637)
- got rid of the "soul" from all things in world
- for Aristotle "soul" explained natural motions, growth of trees, babies to men, etc.
- to begin afresh he began by doubting everything esp. Aristotelian teaching
- Beginning point - "Cogito, ergo sum" -
"I think, therefore I am"
- I exist, therefore God exists
- God by definition, never deceives pure reason
- reason tells us world exists, therefore it does
CARTESIAN DUALISM
Created Existence made up of two kinds of thing
- "res extensa" - extended substance
- takes up space, moves, is tangible
- "res cogitans" - thinking substance
- mind or soul; takes up no space
- reaction against Renaissance Naturalism
- mystical, superstitious view of world
- Descartes' world made up of lifeless chunks of matter
- even animals kind of machines
- despite use of scientific method thought senses could be deceived
- therefore reason must provide final check on theory
MECHANICAL PHYSICS
- broke down Aristotle's distinction between natural and artificial bodies (made by humans)
- rules of physics apply BOTH to clocks and trees
- reduced operation of everything in universe to mechanistic explanation
DESCARTES' UNIVERSE
- universe a plenum, made up of matter in motion
- no empty spaces (vacuum) exists
- if one particle moves, others must get out of way
- sets up whirling vortices of matter
- whole solar system one enormous vortex
THREE ELEMENTS:
- smallest particles first element - ether
- larger rounded particles - second element
- both fill up apparently empty space
- largest, third element
- makes up stars, planets
- fast moving particles set up centripetal pressure
- keeps slower planets in their orbits
THIRD ELEMENT takes many forms
- water is long, thin slippery particles
- earth made of rough, irregular particles
- fire made of sharp, pointed particles
- air made of smaller, light, round particles
- light - pressure of vortices from sun on eyeball
- magnetism - corkscrew-shaped particles fit in corkscrew-shaped pores in magnets, iron
- repulsion arises from left & right-handed corkscrews