His success as an orator, however, was not immediate. He tasted all the bitterness of failure on more than one occasion; but after temporary discouragement he redoubled his efforts to correct the faults that were made so distressingly plain to him by the unsparing but salutary criticism of his audience. Without doubt, these conflicts and rebuffs of his earlier years served to strengthen and deepen the moral character of Demosthenes, as well as to improve his art. They contributed to form a man capable of spending his whole life in unflagging devotion to a high purpose, and that in the face of the greatest difficulties and dangers. The dominant purpose of his life was the preservation of the freedom of the Greek States from the control of any foreign power, and the maintenance of the pre-eminent position of Athens among these States. In this combination of a splendid intellect, an indomitable will, and a great purpose, we find the true basis of Demosthenes's greatness.
When at the age of eighteen he came into the wreck of his patrimony, he at once began suit against Aphobos, one of his unfaithful guardians. He conducted his case himself. So well did he plead his cause that he received a verdict for a large amount. He seems, however, owing to the trickery of his opponent, never to have recovered the money. He became now a professional writer of speeches for clients in private suits of every kind, sometimes appearing in court himself as advocate.
In 355-354 B.C. he entered upon his career as public orator and statesman. He had now found his field of action, and till the end of his eventful life he was a most prominent figure in the great issues that concerned the welfare of Athens and of Greece. He was long unquestionably the leading man among the Athenians. By splendid ability as orator and statesman he was repeatedly able to thwart the plans of the traitors in the pay of Philip, even though they were led by the adept and eloquent Æschines. His influence was powerful in the Peloponnesus, and he succeeded, in 338 B.C., in even uniting the bitter hereditary enemies Thebes and Athens for one final, desperate, but unsuccessful struggle against the Macedonian power.
Demosthenes soon awoke to the danger threatening his country from the barbarian kingdom in the north, though not even he understood at first how grave was the danger. The series of great speeches relating to Philip--the First Philippic; the three Olynthiacs, 'On the Peace,' 'On the Embassy,' 'On the Chersonese'; the Second and Third Philippics--show an increasing intensity and fire as the danger became more and more imminent. These orations were delivered in the period 351-341 B.C.