Isæus is, like Wordsworth's cuckoo, 'a voice, a mystery,' for, though we have ten of the fifty speeches he composed, we know absolutely nothing of the facts of his life, except that he pursued the profession of speech-writer in Athens, and that his first speech was composed in 389 B.C. and his last in 353 B.C., so that he may be said to have lived from the time of the Peloponnesian war to that of Philip's supremacy. Isæus did not compose political speeches, or speeches to be delivered in public suits, but exclusively speeches for private suits.
His strength as a lawyer lay in his power of dealing with cases of inheritance, and it is fortunately those of his speeches which deal with this branch of Attic law that have survived to our times. To the student of Aryan institutions and of comparative law, as well as to the student of Attic law, they are invaluable. To the general reader they are less interesting, for the very nature of the cases in which they were delivered—disputes as to meum and tuum—forbade any very lofty flights of eloquence. On the other hand, the functions which he discharged in the history of Greek oratory as a branch of literature were of the utmost importance, and explain the fact that he was included in the ‘canon’ of the ten great Greek orators. It was through Isæus that the change from the older style of Lysias to the new school of which Demosthenes is the greatest representative was effected. He imitated Lysias, and was himself the teacher of Demosthenes. It will be remembered that Demosthenes’ first speeches were those delivered by him in his efforts to recover his inheritance, the branch of the law in which Isæus was acknowledged master. The characteristics of the two schools between which Isæus was the connecting link are to be seen in the natural tones of Lysias contrasted with the technical skill of the professional orator which along with higher gifts marks Demosthenes. The importance of this contrast becomes apparent when it is remembered that the speech-writer or logographer was not allowed by Athenian law to speak himself on behalf of his client, but only to compose speeches to be delivered by his client. When speech-writing first became a profession and a branch of literature—i.e. about the beginning of the Peloponnesian war—there was a prejudice in the mind of the average Athenian jurymen against the use of speeches thus written, which made it desirable that the speech should have the appearance of being the speaker’s own composition. In adapting his style to the character of his client for the time being Lysias was unrivalled. By the time of Demosthenes the practice of logography was so usual that attempts at disguise were less necessary; and the speech-writer might display all the technical skill of oratory without arousing suspicion. Isæus endeavours to imitate the unprofessional and innocent style of Lysias, but does not succeed in concealing the hoof of the advocate: his simplicity is exaggerated, his sentences have not the careless ease of Lysias, but an ungraceful negligence. At the same time we find in him the germs of that combination of practical utility and artistic beauty which was afterwards to mark the new school. Nor can it be doubted that Isæus surpasses Lysias, as he is himself surpassed by Demosthenes, in pure oratorical skill. Lysias is distinguished for simple colouring but graceful drawing, Isæus for careless drawing but deeper shade, brighter light, and greater wealth of colour. The editio princeps is that of Aldus (1513). The best edition and commentary (German) is that of Schömann (1831).