Dion of Syracuse (dĪˈən) [key], 409?–354? B.C., Sicilian Greek political leader, brother-in-law of Dionysius the Elder, tyrant of Syracuse. He became interested in philosophy through his acquaintance with Plato. Opposed to tyranny, Dion endeavored to set up a moderate system of government with Dionysius the Younger as the model prince. He thus became unwelcome at court and retired (366 B.C.) to Athens. Learning that Dionysius the Younger had taken measures against him, Dion assembled an armed force and sailed to Sicily. He was well received by the people and in 357 B.C. defeated Dionysius in battle. A rival, Heracleides, procured Dion's exile, but Dion was recalled, and he assumed control. He was murdered by an Athenian, a former companion.
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