The Sun at the Horizon, Anaxagoras’ Proof of the Flatness of the Earth
Most Presocratics believed that the earth is flat, shaped like a drum, as we see in Chap. 4. In On the Heavens 293b34 ff. Aristotle argues with those who maintain that the earth is flat, until he finally, in 298b20, considers the case for a spherical earth as settled. Reading those pages, one can still feel how vehement and also how complicated the discussion must have been. As nobody was able to go up into outer space and see what the earth really looks like, one had to take refuge to arguments, varying from common sense to the evidence of the senses, alleged physical laws, and even metaphysics. As a matter of fact, the defenders of a flat earth had common sense on their side: what would prevent us, and especially our antipodes, from falling off a spherical earth? A particular difficulty was that sometimes both parties shared their presuppositions. One party argued, for instance, that the earth must be flat because it is at rest, motionless at the center of the cosmos, all the other celestial bodies circling around it (On the Heavens 294a10 and 294b13 ff.). The idea was, obviously, that a spherical earth could easily roll away, as Simplicius remarks (In Aristotelis De caelo commentaria, 520.13–14). This argument was a tough one, as the defenders of a spherical earth generally shared the supposition that the earth is immovable at the center of the cosmos. In this chapter, I discuss more thoroughly another argument, in which Anaxagoras in defense of the flatness of the earth appeals to a fact from sense experience. I intend to show that the argument is more sophisticated than it seems at first sight. In trying to understand what is meant, I refer to Simplicius’ commentary that is sometimes, although unfortunately not always, elucidating. Thereupon, I discuss Aristotle’s counterarguments, one of which proves to be unsatisfactory, and the other correct.
KeywordsThought Experiment Visible Horizon Curve Line Optical Illusion Greek Text
- Euclid. 1895. Euclidis Optica, Opticorum Recensio Theonis, Catoptrica, cum Scholiis Antiquis. Johan-Ludvig Heiberg, ed., Lipsiae: In Aedibus B.G. Teubneri.Google Scholar
- Mueller, Ian. transl. 2005. Simplicius on Aristotle’s “On the Heavens” 2.10–14. Ithaca, NY: Cornell University Press.Google Scholar
- Panchenko, Dmitri. 1997. Anaxagoras’ Argument Against the Sphericity of the Earth. Hyperboreus 3: 175–178.Google Scholar