1. Using Principles of Logic to Strengthen Argument Writing
Logic in Writing
Using Principles of Logic to Strengthen Argument Writing

2. Review of Argument An argument is a claim supported by evidence
An argument uses logic to make and support a claim
An argument is not a fight

3. Why Use Logic?
Logic strengthens arguments and makes them harder to counter
Logic helps organize writing so that the message is clear
An argument based on logic is difficult to deny or go against

4. Logic Vocabulary Premise – proposition used as evidence in an argument
Must be an agreed upon fact*
Examples: All human beings are mammals. All triangles have three sides.
Premises are strung together to build an argument
Conclusion – logical result that arises from the connection between premises
Usually the main claim (or thesis) of the paragraph or essay
Should be undeniable if the premises are correct and put together in an organized way

5. Building a Logical Argument
Start with a premise (fact)
Explain the premise so that it is clear and there are no questions
Add another premise that builds off of the first one
Explain the second premise, including how it relates to the first one so that it is clear and there are no questions
If necessary continue adding premises and explanations until your point becomes the only logical conclusion
State your conclusion clearly

6. Visual Analogy to Building a Logical Argument
Think of constructing a logical argument like building a wall
Each premise (fact) is like a brick
You need many bricks to build a solid wall just like you need many facts to build a solid argument
BUT…
You also need cement (explanations) to make the bricks stick together

7. Continuing the Analogy
If your “bricks” (facts) are faulty or weak, your wall will crumble easily
Also, if your “cement” (explanations) are inadequate or not present, your wall will crumble easily

8. Finishing the Analogy
You need solid bricks (facts) held together with strong cement (explanations) in order to construct a sturdy wall (argument)
If you construct your argument correctly, it will be almost as unbreakable as a brick wall.

9. What Are Logical Fallacies?
Common errors in reasoning that make an argument illogical
Can be illegitimate arguments or irrelevant points
Can be based on an incorrect premise or a faulty conclusion from premises
Lack evidence and/or do not support claims

10. Types of Logical Fallacies
Slippery Slope – The conclusion assumes that if a premise happens, then through a series of steps, eventually something catastrophic will happen
Example: If we use self-driving cars, then eventually robots will take over all aspects of our life until we can no longer work because robots have taken our jobs. Therefore, we should not use self-driving cars in order to preserve our jobs.
Hasty Generalization – Conclusion based on insufficient evidence
Example: One of the symptoms of mercury poisoning is trembling hands. My hands are shaking right now, therefore, I must have mercury poisoning.

11. Types of Logical Fallacies (Continued)
Post hoc ergo propter hoc – assumes if A happened before B, then A caused B.
Correlation does not imply causation!
Example: I ate pizza and then there was a snow storm, therefore, eating pizza causes snow storms.
Straw Man – oversimplifies the opponents point of view and then attacks that made up argument
Example: People who do not vote to increase military funding want us to be unsafe.

12. Types of Logical Fallacies (Continued)
Circular Argument – restates the argument in other words rather than proving it.
Example: This restaurant is really popular because a lot of people like it.
Ad Hominem – argument attacks the character of a person rather than his or her opinions or ideas
Example: My sister says that math is important but she is dumb and smells bad.

13. Logical Fallacy (“Penguin Logic”)

14. More Penguin Logic…
One of my favorite illogical arguments goes like this:
(See if you can find the fallacy that makes the conclusion untrue.)
Premise 1: No cat has two tails.
Premise 2: One cat has one more tail than no cat.
Conclusion: One cat has three tails.

15. One More Example of Penguin Logic…

16. One More Example of Penguin Logic…

17. In Conclusion…