Euphraeus

Euphraeus (Ancient Greek: Εὐφραῖος; fl. c. 4th century BCE; d. ca. 342 BCE/341 BCE) was a philosopher and student of Plato from the town of Oreus in northern Euboea. He appears to have been active in politics in addition to his speculative studies, being first an adviser to Perdiccas III of Macedon and then an opponent of Philip II and his supporters in Oreus. Information regarding his life is scant, however, and few facts about it are mentioned in more than one source. He appears in the Fifth Letter of Plato, Demosthenes' Third Philippic, and Athenaeus' Deipnosophistae (which repeats the information about him contained in the now-lost Historical Notes by Carystius of Pergamum).

None of the sources that mention him say anything about his family or early life. Most of what is known about him involves his political activity.

Little is said about Euphraeus in the Fifth Letter of Plato beyond his aptitude for political philosophy, and the letter's authenticity has been challenged. The letter commends Euphraeus to Perdiccas III, king of Macedon. This story, at least, is supported by Carystius, who cites a letter supposedly by Speusippus (Plato's nephew and successor as head of the Academy) that Philip II should cease slandering Plato because he owes him his kingship, if rather backhandedly. Plato, the story goes, sent Euphraeus to Perdiccas, Euphraeus counselled that he grant a principality to his brother Philip, and Philip's military occupation of this land enabled him to seize power following Perdiccas' death.

...
Wikipedia