It is the philosopher Plato who is the one source for all subsequent speculations about Atlantis' existence. As a young man he was a disciple of Socrates. After the latter's death he presided over a circle in Athens, and wrote imaginary conversations or 'dialogues' portraying Socrates talking with friends. Some of these may have been true to life; in others, Plato uses the characters as mouthpieces for teachings and stories of his own. Two of the dialogues are entitled Timaeus and Critias after the principal speakers in them. Passages in both tell of an island-continent in the western ocean. Formerly a domain of the sea-god Poseidon, it was named Atlantis after Atlas the Titan, said to have been Poseidon's son. It had a magnificent ornate capital, and its people made use of gold, silver, bronze and tin, and also orichalcum, a mysterious alloy, in fashioning their civilization. Atlantis' kings were conquerors of parts of Europe, Africa, and a trans- Atlantic continent. The Athenians were at last successful in defeating them. Then, in a cataclysm of flood and earthquake, Atlantis sank bodily beneath the sea.