Informal Logic & Fallacies
Informal Logic
Dissecting an Argument
Informal Logic Fallacies A
Arguments attempt to discredit an individual or a group rather than focus on the issue at hand
Ad Hominem (Attack on the Person)
Attacking the arguer and not his/her argument
George W. Bush may have his reasons for going into Iraq, but he is an idiot. Whatever his reasons, they are bound to be wrong.
Appeal to Tradition
Premise must be true because people have always believed or done it
I know that it’s inequitable that a woman is expected to change her name when she marries, but that’s our tradition, so it’s not sexist.
Attack on the Motive
Attacking the credibility of a person on the grounds that they have bias/motive influencing their view
Ned James claims that he can prove that Mayor Babcock has embezzled city funds. But James is just trying to get back at the mayor for firing him from his job as city controller.
Bandwagon
Appealing to popularity or the fact that many people do something as an attempted form of validation; majority of people believe an argument so it must be true
Straw Man
Misinterpreting someone’s argument to make it easier to attack
Caroline says that she thinks her friends should not be so rude to the new girl. Jenna says that she cannot believe that Caroline is choosing to be better friends with the new girl than the girls who have always known her.
Informal Logic Fallacies B
Focuses on the structure of an argument and the way terms are used
Appeal to Ignorance
Lack of evidence argument used in 2 forms
1 - There is no evidence, so it can’t be true
2 - There is no evidence for it being false, so it is true
Begging the Question
A circular argument in which the conclusion is included in the premise
Example
My mom never lies to me
*How do you know?
She told me
Equivocation
An argument that uses one word to mean two different things
Loaded Term
Using words/terms with strongly positive or negative connotations
“You slowly murder your children when you feed them fast food”
Slippery Slope
Asserting that if we allow A to happen, then Z will happen subsequently too, therefore A should not happen
Informal Logic Fallacies C
Deal with specific-general and part-whole relationships
Accident
Exceptional (or accidental) factors are overlooked while arguing that a general rule should be applied.
Applying a general rule to all situations.
I believe one should never deliberately hurt another person, that’s why I can never be a surgeon.
Explanation: Classifying surgery under “hurting” someone, is to ignore the obvious benefits that go with surgery. These kinds of extreme views are rarely built on reason.
Hasty Generalization
Using an unrepresentative sample to conclude a general rule
Composition
Assuming that what’s true about one part of something has to be applied to all.
Part to Whole.
Each part of the engine weighs very little, so the engine must be lightweight
Decomposition
Opposite of composition. Assuming a feature/property of the whole has to be applied to each part.
Whole to Part.
The play was given a rave review, so the minor part played by Mimi must have been superb.
QUIZ
Despite the cost, impending gas crisis, and the harm to the environment, it is desirable to own an SUV because successful people do.
Bandwagon
If Canada legalizes marijuana, eventually everyone will start smoking it regularly and other kinds of drugs will become legal
Slippery Slope
That candidate smoked pot when he was in college, therefore, he should not be president.
Ad Hominem
“Attacking the Man”