Born the son of a wealthy sword-maker, Demosthenes was orphaned at the age of seven. His father left him well-provided-for, but his legal guardians defrauded him and squandered his inheritance, causing him to seek retribution through the courts when he came of age.
As a boy Demosthenes suffered from a speech impediment and he worked at a series of self-designed exercises to overcome it. A common story tells of his talking around mouthfuls of rocks to improve his diction, but it is unknown whether this is fact or merely a legendary example of his perseverance and determination. Either way, Demosthenes became a prominent political orator (speech-maker), making his living through his ability to write and make speeches. He is best-known for his Philippic Orations, urging the populace to rise up and defend their country against Philip II of Macedon, who was steadily gaining power and territory for the Macedonian state.
Demosthenes's speaking style was relatively straightforward and generally without rhetorical flair. It was considered somewhat vulgar by the standards of the day, but was nevertheless very popular. He also made use of his body to accentuate his words, and as a result was able to project his ideas and arguments much more forcefully (later famous orators like Henry Clay would mimic this technique). Although Demosthenes's arguments were the products of careful study and preparation -- he often declined to comment on subjects he had not studied beforehand -- he was famous for his sharp wit, and his name has been used to imply a particularly venomous rejoinder.
Demosthenes was exiled after a convoluted affair involving money taken by one of the lieutenants of Alexander the Great. He was recalled to Greece after Alexander died, where he attempted once again to rally the Grecian people against Macedonia, but he was unsuccessful and took poison rather than face capture and punishment.