The Pythagorean Philosophy of Harmony

Phililaus uses the diatonic musical scale to show how this works, from the unlimited continuum of all possible sounds. Limits and unlimited are opposites, so they must have a bond which somehow allows them to work together if they're to form a coherent whole. Phililaus also came up with what is the earliest attested cosmology, which prefigures modern ideas of the solar system in some respects. And last but not least, he included the counter-Earth, the Antichthon, which Aristotle thinks he just included to make the number of heavenly bodies add up to ten.