1. Logical Fallacies
English II

2. Logical Fallacies Logical fallacies are errors of reasoning.
“Fallacy” means falsehood.
These arguments affect our ability to think critically
They can be used to distract us from the actual issue or to persuade us through manipulation.
Although these arguments may sound persuasive and may seem correct, some part of the argument is flawed.

3. Types of Logical Fallacies
Circular Reasoning: (also known as Begging the Question)- creates a “circle” in which no useful information is being shared.
Interviewer: "Your resume looks impressive but I need another reference."  Bill: "Jill can give me a good reference."  Interviewer: "Good. But how do I know that Jill is trustworthy?"  Bill: "Certainly. I can vouch for her."
Example

4. Types of Logical Fallacies
Over-simplification: ignores the complexities, variations, and exceptions relevant to an issue
“Taxation is theft!”
Crime: it all boils down to poverty.
Example

5. Types of Logical Fallacies
Over-generalization (also called Hasty Generalization) - An argument from insufficient evidence or from too small a sample. Look for key words like “all,” “always,” and “every”
“Bullying doesn’t exist in this school because I have never seen it.”
My father smoked four packs of cigarettes a day since age fourteen and lived until age sixty-nine.  Therefore, smoking really can’t be that bad for you.

6. Types of Logical Fallacies
Self-contradiction: When the argument contains parts that refute each other, making truth impossible
"The only thing that is certain is uncertainty.”
By definition, uncertainty cannot be certain.

7. Types of Logical Fallacies
False Causality- (also known as Post Hoc Ergo Propter Hoc) this is the classic error that assumes that simply because B followed A, B was caused by A.
“Before women got the right to vote, there were no nuclear weapons.”
Example #1

8. Types of Logical Fallacies
Appeal to Ignorance: A claim that whatever has not been proven false is true and vice versa.”
“9/11 must be a government conspiracy because there is no convincing evidence that it wasn’t.”
Flip side: “The attacks on 9/11 were not a government conspiracy because there is no proof it was.”
Example

9. Types of Logical Fallacies
Slippery slope: The argument that if X happens, then Y and Z will surely follow, when there’s no clear connection between X, Y, and Z.
“If we make assault rifles illegal, next they’ll want to outlaw hunting rifles, kitchen knives, and heaven knows what else.”
Example

10. Types of Logical Fallacies
False dilemma: (also called Either-Or Fallacy)- the argument that there are only two possible answers to a complicated question, one usually terrible.
“If we don’t prohibit text messaging from our classes, then no one will learn anything in them.”
“America: love it or leave it!”
Example #1
Example #2

11. Types of Logical Fallacies
Faulty analogy: The argument that because two things are alike in one respect, they are alike in other respects as well.
"If advertising for tobacco becomes illegal, then we should outlaw advertising for milk and eggs because they contain cholesterol, a harmful substance.”
“Employees are like nails. Just as nails must be hit in the head in order to make them work, so must employees.
Example

12. Types of Logical Fallacies
Stacking the deck: an argument that ignores or significantly downplays facts or evidence contrary to one’s position and highlights points that support it.
A poster for the U.S. Navy focuses upon an impressive picture, with words such as "Travel" and "Adventure", while placing the words "Enlist today for 2,3, or 4 years" at the bottom in smaller and less noticeable font.
They also don’t mention that you will leave your family for months at a time.

13. How to locate logical fallacies
Pretend you disagree with the author’s conclusion.
What parts of the argument would now seem fishy to you? What parts would seem easiest to attack? In your own writing, give special attention to strengthening those parts.
List the author’s main points; under each one, list the evidence the author provides.
Seeing claims and evidence laid out this way may make you realize that the author has no good evidence for a particular claim.
It also may help you look more critically at the evidence, especially in your own writing.
Learn which types of fallacies you're especially prone to, and be careful to check for them in your work.
Some writers make lots of overgeneralizations; others are more likely to rely on weak analogies or offer circular reasoning.

14. How to find fallacies in your own writing
Be aware that broad claims need more proof than narrow ones.
Claims that use sweeping words like "all," "no," "none," "every," "always," "never," "no one," and "everyone" are sometimes appropriate—but they require a lot more proof than less-sweeping claims that use words like "some," "many," "few," "sometimes," "usually," and so forth.
Double check your characterizations of issues to be sure they are accurate and fair.