1. Plato, 48e–53c
2. Aristotle, Book IV
3. Lucretius, Book I
4. Aquinas, I, Q. 52
5. Descartes, Part II
6. Newton, , Scholium to Definitions
7. Leibniz,
8. Locke, Book II, Ch. 13
9. Kant, , Transcendental Aesthetic
10. Hegel, , Philosophy of Nature §§254–256