Nov 30 The Mechanical Philosophy
Rene Descartes 1596-1650
What’s the world made of?
•Mechanical philosophy provides a comprehensive alternative to Aristotle’s substantial forms (matter + form).
•Postulates a minute, invisible substratum by which all objects, phenomena are explained.
Main features of the mechanical philosophy
1. Whole universe operates like a machine.
2. Matter is composed of tiny particles.
3. Nature is fundamentally mathematical.
Machine analogy
The world and everything in it are just like clockwork.
Built of complex material parts in certain configurations and interactions.
Runs automatically.
Technology influences science
•Descartes: “There is no difference between the machines built by artisans and the diverse bodies that nature alone composes.”
Automata
•Living organisms are exactly like mechanical, artificial versions of themselves.
•Robot, moving statue = automaton.
•All living functions arise from parts, arrangement, movements.
Particles or “corpuscles” or “atoms”
•The underlying machinery of nature is corpuscular. Everything is made up of tiny pieces of matter of various dimensions.
•Revival of ancient atomism.
•The corpuscles are beyond our sense perception.
•They combine, impact, separate.
•They interact only by direct contact (no action at a distance).
•Their composition and interactions account for all observable phenomena.
Mathematical nature
•Corpuscles have ONLY these properties:
–Size
–Shape
–Motion
•These can all be quantified, measured. Dimensions, distances, speed, rotation, etc.
•Hence Descartes the mathematician has
mathematized the world at its most basic level.
•Descartes: “Give me extension & motion and I will build the world.”
–How does he actually use math/geometry?
•Galileo: “Motion is subject to the law of number.”
–Experiments deal only with measurable features of nature, like distances, times, weights. Simplify the real world.
Primary vs. secondary qualities
•Distinction made by Galileo & Descartes, in opposition to Aristotle’s doctrine of forms (qualities were not explained).
•Dimension and motion are the only qualities inherent in objects themselves. Thus only quantity is real.
•Everything else is merely subjective.
–Sensible qualities (appearances of things) don’t exist outside of the mind of the observer. Color, odor, heat, etc have no physical reality.
•There is no objective quality or form of “sweetness.” Mechanical philosopher says that honey is made of particles with size/shape that give the tongue a sensation of sweetness.
•“Heat” is likewise only a secondary quality, our perception of it caused by the fast motion & impact of fire particles.
Descartes’ method
•He KNOWS that the natural of matter is extension & motion because these are “clear & distinct ideas” in his mind (God would not deceive).
•From that “certain” first principle as the foundation for his system, he can logically deduce conclusions = “perfect knowledge of physical nature.”
•Contrast with Bacon’s emphasis on induction, empiricism, experiment.
Putting the MP approach into practice
•Speculative, a priori accounts of hypothetical corpuscles that might cause a given phenomenon.
•How to invent these theories, how to choose the most plausible, how to sound convincing?
•By analogies with familiar mechanical devices and effects.
•Understand the hidden substratum based on everyday experiences, intuition, illustrations.
Examples of theories: vortex
•Planets are pushed in their orbits as if in a huge whirlpool = vortex theory.
•Plenum = universe is full of matter, and particles bump each other in closed circles.
Magnetic attraction = caused by corkscrew particles
Light = secondary quality
•Light is sensed as a pressure against the eye transmitted thru particles.
–Everyday analogy as evidence: press against your eyelid & see light.
•Color = perceived effect of the motion of particles, spinning slower (blue) or faster (red) or not at all (black).
•Theory of vision = transmission of particles thru hollow nerves, from the eye to the brain.
Anything goes?
•Ad hoc tendencies make the MP very easy to apply to any specific phenomenon & thus very popular in broad outlines
•“Posit the existence of sub-microscopic particles of whatever particular shape or size wanted for the purpose.”
•How can such a science be verified or refuted?!
•Acids burn because they are composed of sharp pointy corpuscles that scrape. To a mechanical philosopher, this is preferable to Aristotle saying that acids have an “acidic quality.”
•Opium causes sleepiness not because of its “soporific quality,” but because of how its particles affect the brain.
•Keen to explain natural magic without using sympathies, correspondences