1. Logic in Argumentative Writing

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

3. 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.

4. 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.)

6. 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.

7. Faulty Logic

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

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