Plato 
Gorgias [PDF ebook] 

Gorgias is a Socratic dialogue written by Plato around 380 BC. The dialogue depicts a conversation between Socrates and a small group of sophists (and other guests) at a dinner gathering. Socrates debates with the sophist seeking the true definition of rhetoric, attempting to pinpoint the essence of rhetoric and unveil the flaws of the sophistic oratory popular in Athens at the time. The art of persuasion was widely considered necessary for political and legal advantage in classical Athens, and rhetoricians promoted themselves as teachers of this fundamental skill. Some, like Gorgias, were foreigners attracted to Athens because of its reputation for intellectual and cultural sophistication. In the Gorgias, Socrates argues that philosophy is an art, whereas rhetoric is a skill based on mere experience. To Socrates, most rhetoric is in practice merely flattery. To use rhetoric for good, rhetoric cannot exist alone. It must depend on philosophy to guide its morality, he argues. Socrates therefore believes that morality is not inherent in rhetoric and that without philosophy, rhetoric is simply used to persuade for personal gain. Socrates suggests that he is one of the few Athenians to practice true politics (521d).
The dialogue begins just after Gorgias has given a speech. Callicles says that Gorgias is a guest in his home, and has agreed to a private audience with Socrates and his friend Chaerephon. Socrates gets Gorgias to agree to his cross-examination style of conversation. Gorgias identifies his craft as rhetoric, and affirms that he should be called a rhetorician. As Socrates asks him questions, he praises him for the brevity of his replies. Gorgias remarks that no one has asked him a new question in a long time, and when Socrates asks, he assures him that he is just as capable of brevity as of long-windedness (449c).