It is widely accepted that Plato, the Athenian philosopher, was born in 428-7 B.C.E and died at the age of eighty or eighty-one at 348-7 B.C.E. These dates, however, are not entirely certain, for according to Diogenes Laertius (D.L.), following Apollodorus’ chronology, Plato was born the year Pericles died, was six years younger than Isocrates, and died at the age of eighty-four (D.L. 3.2-3.3). If Plato’s date of death is correct in Apollodorus’ version, Plato would have been born in 430 or 431. Diogenes’ claim that Plato was born the year Pericles died would put his birth in 429. Later (at 3.6), Diogenes says that Plato was twenty-eight when Socrates was put to death (in 399), which would, again, put his year of birth at 427. In spite of the confusion, the dates of Plato’s life we gave above, which are based upon Eratosthenes’ calculations, have traditionally been accepted as accurate.
Family
Little can be known about Plato’s early life. According to Diogenes, whose testimony is notoriously unreliable, Plato’s parents were Ariston and Perictione (or Potone—see D. L. 3.1). Both sides of the family claimed to trace their ancestry back to Poseidon (D.L. 3.1). Diogenes’ report that Plato’s birth was the result of Ariston’s rape of Perictione (D.L. 3.1) is a good example of the unconfirmed gossip in which Diogenes so often indulges. We can be confident that Plato also had two older brothers, Glaucon and Adeimantus, and a sister, Potone, by the same parents (see D.L. 3.4). (W. K. C. Guthrie, A History of Greek Philosophy, vol. 4, 10 n. 4 argues plausibly that Glaucon and Adeimantus were Plato’s older siblings.) After Ariston’s death, Plato’s mother married her uncle, Pyrilampes (in Plato’s Charmides, we are told that Pyrilampes was Charmides’ uncle, and Charmides was Plato’s mother’s brother), with whom she had another son, Antiphon, Plato’s half-brother (see Plato, Parmenides 126a-b).
Plato came from one of the wealthiest and most politically active families in Athens. Their political activities, however, are not seen as laudable ones by historians. One of Plato’s uncles (Charmides) was a member of the notorious “Thirty Tyrants,” who overthrew the Athenian democracy in 404 B.C.E. Charmides’ own uncle, Critias, was the leader of the Thirty. Plato’s relatives were not exclusively associated with the oligarchic faction in Athens, however. His stepfather Pyrilampes was said to have been a close associate of Pericles, when he was the leader of the democratic faction.
Plato’s actual given name was apparently Aristocles, after his grandfather. “Plato” seems to have started as a nickname (for platos, or “broad”), perhaps first given to him by his wrestling teacher for his physique, or for the breadth of his style, or even the breadth of his forehead (all given in D.L. 3.4). Although the name Aristocles was still given as Plato’s name on one of the two epitaphs on his tomb (see D.L. 3.43), history knows him as Plato.