Logic in Argumentative Writing

Logic in Writing Logic is a formal system of analysis that helps writers invent, demonstrate, and prove arguments.

Logical Vocabulary Premise: Proposition used as evidence in an argument. Conclusion: Logical result of the relationship between the premises; conclusions serve as the thesis of the argument. Argument: The assertion of a conclusion based on logical premises. Syllogism: The simplest sequence of logical premises and conclusions, devised by Greek philosopher Aristotle.

Aristotle’s Famous Syllogism Premise 1: All men are mortal. Premise 2: Socrates is a man. Conclusion: Therefore, Socrates is mortal. (Premise 2 is tested against premise 1 to reach the logical conclusion.)

Example of a modern syllogism: The goal of a syllogism is to arrange premises so that only one true conclusion is possible. Example of a modern syllogism: Premise 1: Non-renewable resources do not exist in infinite supply. Premise 2: Coal is a non-renewable resource. Conclusion: Coal does not exist in infinite supply.

Faulty Logic

Logical Fallacies Slippery Slope: A conclusion based on the premise that if “A” happens, then eventually through a series of small steps, “B”, “C”, …. “Z” will happen, too, basically equating “A” and “Z”. As a result, the conclusion asserts if we do not want “Z” to occur, “A” must not be allowed to occur either. Example: If we ban Hummers because they are bad for the environment, eventually the government will ban all cars, so we should not ban Hummers.

Logical Fallacies Overgeneralization: This is a conclusion based on lumping a group of people—for example, Moslems or Christian. This stereotyping of a group of people is untrue and can appear bigoted. Examples: All Moslems are terrorists. Republicans are gun-toting, bible carrying citizens who are out of touch with modern America.

Logical Fallacies— Type of Overgeneralization Hasty Generalization: This is a conclusion based on insufficient or biased evidence. In other words, you are rushing to a conclusion before you have all the relevant facts. Example: Even though it is only the first day of class, I can tell this is going to be a boring course.

Logical Fallacies Post hoc ergo propter hoc (After this, therefore because of this): This is a conclusion that assumes that if “A” occurred after “B” then “B” must have caused “A”. Examples: If you eat Subway everyday, you will become thinner. I drank bottled water and now I am sick, so the water must have made me sick.

Logical Fallacies Circular Reasoning: This restates the argument rather than actually proving it. Examples: George Bush is a good communicator because he speaks effectively. Making paper airplanes is a waste of time because it squanders much valuable time.

Logical Fallacies Either/or: This is a conclusion that oversimplifies the argument by reducing it to only two sides or choices. Examples: People can either stop using cars or destroy the earth. Either Americans can build a wall between Mexico and the United States, or the economy will be ruined.

Logical Fallacies Ad hominem(To the man): This is an attack on the character of a person rather than his or her opinions or arguments. Example: Green Peace’s strategies are not effective because they are all dirty, lazy hippies.

Logical Fallacies Ad populum(To the people): This is an emotional appeal that speaks to positive—patriotism— or negative concepts—fascism— rather than the real issue at hand. Example: If one is a true American, he or she would support the rights of people to choose whatever vehicle they want.

Logical Fallacies Red Herring: This is a diversionary tactic that avoids the key issues, often by avoiding opposing arguments rather than addressing them. Example: The level of mercury in seafood may be unsafe, yet fishers support their families with their incomes.

Logical Fallacies Straw Man: This move oversimplifies an opponent’s viewpoint and then attacks that hollow argument. Example: People who do not support the proposed state minimum wage increase hate the poor.

Logical Fallacies Moral Equivalence: This fallacy compares minor misdeeds with major atrocities. Example: The parking attendant who gave me a ticket is as bad as Hitler.

Using Logic in Writing Before writing your argumentative essay, you must plan a logical sequence of argument: 1. Lay out each premise clearly. 2. Provide evidence for each premise. 3. Draw a clear connection to the conclusion.

Premise 1: Minimum wage should match the cost of living in society. Premise 2: The current minimum wage does not match the cost of living in society. Conclusion: Therefore, minimum wage should be increased. __________________________________________ NOTE: Once the syllogism has been determined, you need to elaborate each step in writing, which provides evidence for the premises. Look at the handout that I gave you that briefly expands on the premises and draws a conclusion.

Works Cited “Logic in Argumentative Writing.” Purdue Owl. Purdue University, 2011. Web. 14 February 2010.