In the 4th century BCE, Greek philosopher Aristotle authored "Rhetoric," a tome in which he articulated methods to present evidence in order to persuade audiences. One of the three types of appeals used in an argument is "logos," or a logical appeal based on reasoning. Examples of logical appeal in persuasive writing reveal an array of techniques to introduce evidence.
Definitions and Terms
A logical appeal can pivot on a definition or claim, regarding the property or nature of something. For example, nuclear activists may point to the lethal nature of radioactive fallout as an appeal for disarmament. They must describe the actual properties of nuclear weapons in order to convince audiences of the harm caused to human and animal life as well as the environment. The activist must also explain terms, such as radioisotopes, the cloud seeding effect and blast injuries, used in making claims about nuclear weapons.
Comparison and Analogy
The use of comparison or analogy based on evidence can either prove or refute an argument. In the example of a persuasive essay about anti-vivisectionists on the Custom Essay Lab website, the author notes that while anti-vivisectionists condemn the killing of animals, the majority of them are meat-eaters. A comparison is then made to the meat packing industry that conducts mass animal slaughter on a regular basis, thus exposing the hypocrisy. As a retort, the vivisectionists can compare the pain and anxiety suffered by animals awaiting slaughter to that of humans in line for execution. Lawyers typically use parallel cases to buttress an argument in court.
Cause and Consequences
When people make logical appeals to advocate new policies up for debate, they typically point to the consequences of actions either taken or avoided. In the 1996 State of the Union Speech, President Bill Clinton tried to convince Congress to pass a requirement for the V-chip in TV sets. The device would enable parents to screen for unsuitable content for children. He perceived parental action as personal responsibility, not censorship. The consequences of taking no action would be the children's exposure to possible exploitative and harmful content.
A logical appeal can leverage the testimony or opinions of experts on the argument's subject matter. Such a technique builds credibility. For example, the essay on anti-vivisectionists on the Custom Essay Lab website refers to Albert Schweitzer's acknowledgment that experiments on animals are indispensable to finding cures for human afflictions.
Research and Statistics
The use of research and statistics can be a powerful tool in a logical appeal. You build credibility by not only citing numbers but also leveraging the authority of the institution or scientists responsible for the numbers. The example anti-vivisectionist essay on the Custom Essay Lab website cites that more than "60,000 coronary bypass operations are done annually; their success can be traced to the fact that they were originally performed on animals."
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