Greek and Roman manuals of rhetoric were deeply interested in laughter. Orators could use wit and humor to debunk an argument or an opponent and gain the support and favor of an audience. But laughter is a double-edged sword and can easily backfire; hence various works concerned with rhetoric sought to teach about the nature of laughter, its origins and boundaries, and they classified different typed of jokes, recommending some but not others. As a rule, Greeks and Romans had a high tolerance for aggressive jokes in public speeches, as long as they helped a speaker to be persuasive. When interacting with friends or with diners at a banquet, however, aggressive barbs should be avoided, as shown by Plutarch, who asks the same questions about the nature and causes of laughter, but takes an ethical rather than agonistic perspective.