The time of his birth and death is unknown, but all accounts agree in the statement that he flourished (ἤκμασε) during the period between the Peloponnesian War and the accession of Philip II of Macedon, so that he lived between 420 and 348 BC.
All particulars about his life are unknown, and were so even in the time of Dionysius, since Hermippus, who had written an account of the disciples of Isocrates, did not mention Isaeus at all.
Also, in 1815 Mai discovered and published the greater half of Isaeus' oration On Cleonymus' legacy (περὶ τοῦ Κλεωνύμου κλήρου).
Isaeus is also known to have written a manual on speechwriting entitled the Technē or Idiai technai (ἰδίαι τέχναι, "Personal skills"), which, however, is lost.
[6] List of extant speeches (available at the Perseus Digital Library) Although his orations were placed fifth in the Alexandrian canon, still we do not hear of any of the grammarians having written commentaries on him, except Didymus of Alexandria.