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Full Idea
For Aristotle, aether and the four sublunary elements obey different physical laws. Aether moves naturally in a circle and, unlike its lower counterparts, is not a source of perishability. The four sublunary elements move naturally in straight lines.
Gist of Idea
Aether moves in circles and is imperishable; the four elements perish, and move in straight lines
Source
report of Aristotle (On the Heavens [c.336 BCE]) by Mary Louise Gill - Aristotle on Substance Ch.2
Book Ref
Gill,Mary Louise: 'Aristotle on Substance: Paradox of Unity' [Princeton 1989], p.67
A Reaction
I think it is anachronistic for Gill to talk of 'obeying' and 'laws'. She should have said that they have different 'natures'. We can be amused by Greek errors, until we stare hard at the problems they were trying to solve.
| 16102 | Aether moves in circles and is imperishable; the four elements perish, and move in straight lines [Aristotle, by Gill,ML] |
| 394 | An unworn sandal is in vain, but nothing in nature is in vain [Aristotle] |
| 395 | It seems possible that there exists a limited number of other worlds apart from this one [Aristotle] |
| 396 | There has to be some goal, and not just movement to infinity [Aristotle] |
| 1498 | Everyone agrees that the world had a beginning, but thinkers disagree over whether it will end [Aristotle] |
| 398 | Each thing that has a function is for the sake of that function [Aristotle] |
| 399 | If the more you raise some earth the faster it moves, why does the whole earth not move? [Aristotle] |
| 19740 | A very hungry man cannot choose between equidistant piles of food [Aristotle] |
| 402 | The Earth must be spherical, because it casts a convex shadow on the moon [Aristotle] |
| 403 | The earth must be round and of limited size, because moving north or south makes different stars visible [Aristotle] |
| 17463 | An element is what bodies are analysed into, and won't itself divide into something else [Aristotle] |
| 20918 | Void is a kind of place, so it can't explain place [Aristotle] |