Ancient sources believed Isaeus (i-SEE-uhs) to be from Chalcis in the Chalcidice or Athens; probably he was born in Chalcis and moved to Athens, where he lived as a resident alien (metic). This move must have predated 392 b.c.e. because Isaeus studied under Isocrates, who opened his school in Athens in that year. Isaeus did not take part in political life (further support for his metic status because only Athenian citizens could engage in politics) but instead pursued a career writing speeches for other people. He specialized in inheritance cases and had an expert knowledge of Athenian law. He also taught the art of speechwriting. Among his pupils was a youthful Demosthenes, and all sources testify to Isaeus’s influence on him.
Isaeus is credited with either sixty-four or fifty speeches, but only twelve have survived. His oratorical ability was considered great enough for him to be included in the canon of the ten Attic orators. Although his style is concise like that of his predecessor Lysias, he is not able to portray the individual characteristics of his speakers as well.