Replying to Theaetetus’ suggestion that knowledge is true opinion at Tht. 200e, Socrates remarks that ‘a whole profession’ testifies against this definition. The orator practises the art of persuasion, not to teach people, but make them believe whatever he wants. If a robbery has taken place, for example, he cannot in a short time teach adequately the truth about what happened to people who were not on the scene.