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== Whose Idea Is It? ==

<nomobile>[[File:Capo Colonna2 retouched.png|thumb|The single remaining standing column from the temple of Hera built in Croton in the 5th century BCE]]</nomobile>

If you're still here, then I'm inviting you to yet another travel voyage and time and spice, all the way to Croton, a Greek town at the tip of the Italian boot, in the earlier half of the 5th century BCE. The town's intellectual and religious life is dominated by the sect of Pythagoreans. Yes, this is a time of celebrity mathematicians. Sadly, after '''Pythagoras''' had died, his followers were quick to turn his science into a dogmatic religion, which they observe by praying to numbers and by refraining from eating meat and legumes. Instead of elegant mathematical proofs, they're now content with "the Master said so" as an argument. A few, however, preferring to think for themselves, have managed to wriggle themselves out of the cult. Among them is '''Empedocles of Acraga''', a Greek colony on Sicily. What he's particularly interested in is the structure of matter. Earlier thinker, who lived in Ionia on the western shore of what will once be called Turkey, were trying identify the primordial substance, from which all other matter derives, proposing various specific elements: '''Thales of Miletus''' suggested water; '''Heraclitus of Ephesus''', fire; '''Xenophanes of Colophon''', earth… Empedocles, who proved the existence of air in a simple experiment with a water clock, tried to reconcile them all by proposing not one, but four primordial substances, that is, ''earth, water, air'' and ''fire''. It will take one more generation for Plato to add ''aether'' to this number, so that he can assign to each of the five elements one of the five regular polyhedra, including the recently discovered icosahedron.