Newton (1642-1727)
1. Philosophiae Naturalis Principa Mathematica (1687)
The three laws of mechanics:
- principle of inertia
- equation of motion: F=ma, or F=D(p).
- principle of action-reaction.
The Law of Universal Gravitation: the force between two bodies is proportional to the product of their masses and invrrsely proportional to the square of their distances.
2. Absolute space and time vs. relative space and time.
- Since absolute space amd time are not sensible, we must use sensible measures of them, that is, relative position (space) and uniform motion (time).
- the order of the parts of space and time is immutable
- space is immovable since to move any part of space would amount to taking it out of itself.
- place is the part of space a body takes up: it can be absolute or relative
- motion is translation from one place to another: it can be absolute or relative.
- Absolute and relative motion/rest can (in principle) be distinguished in terms of their different properties (all bodies absolutely at rest are at rest with respect to each other), causes (absolute motion is initially caused by a true force on the body) and effects (absolute circular motion can be detected by the presence of centripetal forces). However, only the distinction based on effects is opne to us (the bucket and the globes experiments).
3. The General Scholium plus Optics, query 31.
A. The argument from design:
Astronomical: The solar system shows divine design.
- The fact that planets move in concentric orbits, on the same plane, and in the same direction cannot be explained by merely mechanical causes because:
- Descartes’ hypothesis of vortices won’t work because of the moon of Jupiter and Saturn and the eccentric motions of the comets.
- comets range all over the heavens, and so might the planets.
NOTE: if each star is a sun, then its planets must be subject to the same wise counsel.
- Since blind metaphysical necessity is the same everywhere and always, it cannot produce any variety.
Biological: the design in animals and their organs shows divine intelligence (query 31).
B. The Lord God Pantokrator
- living, omniscient, omnipotent, infinite, and necessarily existent.
- by existing always and everywhere constitutes time and space.
- God is omnipresent not virtually but substantially. In Him all things move and have their being.
- God is not the soul of the world.
- Space is the sensorium dei (query 31).
Problem: By making space and time attributes of God, has Newton made God divisible and subject to temporal succession?
Answer: no to the first and yes to the second.
Problem: does the fact that God has a sensorium turn him into the soul of the world? The controversy between Clarke and Leibniz.
C. Gravity exists for sure; however, its cause, is unknown: hypotheses non
fingo. Still, Newton not averse to Clarke’s ides that God does the pulling.
NOTE: the issue of action at a distance.
D. Since friction, partial elasticity, viscosity, etc, dissipate motion, it’s
necessary to introduce active principles in matter such as gravitation,
fermentation, and forces of cohesion. Indeed, N’s view is that god must periodically
intervene to add motion to the solar system, which would otherwise run down.
4. Newton’s first letter to Bentley
The whole letter is a protracted astronomical argument from design.
when composing Principia, N. had an eye to providing evidence for God’s existence.
N. answers Bentley’s questions:
- that the sun, which is hot and bright, is at the center of the solar system cannot be explained by natural causes.
NOTE: still, the heat on the earth is probably more caused by fermentation within it than by the solar irradiation
- the motion and disposition of the planets (coplanar, unidirectional, concentric, panets of larger mass being external so as not to disturb the motion of the earth)) shows counsel.
NOTE: however, N. does not consider the tilt of the earth’s axis as manifestation of design.