9 logical fallacies(slideshare)
TRANSCRIPT
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Recognizing Logical Fallacies !
A logical fallacy is a mistake in reasoning; it is a MENTAL TRAP!
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Looking at the Negative Space • We can learn much
about logic by studying that which is not logical—examples of where logic breaks down, logical fallacies.
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1. Over-generalization !• Drawing too wide a conclusion from the
given facts !• Example: !
– All kids cause trouble.!– Timmy is a kid. !– Therefore, Timmy causes trouble.!
Fix this by recognizing qualifiers
(many, few, some, all, etc.)
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2. Arguing in Circles • Def: Supporting an opinion not with evidence but with
the same opinion, slightly disguised (restating the argument in different words). Using the word you’re defining in the definition is a classic example.!
• Example:!– Education is important for kids, so they should get an
education.!– Everybody likes ice cream because it is liked by all.!– “Belligerently” means in a belligerent way.!
Fix it by making sure you are giving support, not just repeating the idea. Never use the
word you’re defining in the definition. !
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3. Black & White Thinking
• Def. An opinion that claims there are only two alternatives (when there might be more)
• Examples: – You’re either for it or against it. – Are you a jock or a nerd?
Fix this by remembering that the world is a complicated place and that on most issues
there are many alternatives.
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4. Red Herring • Def. Presenting an irrelevant topic to divert
attention away from the original issue. • Also known as Ad hominem: getting
personal as you discredit someone. • Examples:
– What do you know? You’re just a kid. – I got an F. Mr. X hates me.
Fix this by staying focused on the topic; watch out for those who don’t.
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5. Loaded Questions and Statements
• Def. A question or a statement that conceals an opinion or assumption.
• Examples: – Do you still beat your dog? – You don’t think that, do you? – All intelligent people agree that …
Fix this by listening carefully and separating fact from opinion.
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6. Statistical Fallacies�& False Authority
• Def. People usually believe in numbers and experts without questioning them. Here statistics are used to misrepresent rather than describe.
• Examples: – 3 out of 4 dentists prefer Crest. (Did Crest pick the dentists?) – I surveyed 100 people and they all agreed with me. (I chose my
friends). – Dr. X says this is the fastest and safest way to lose weight. (Did he/
she get paid? Where do they practice?) Fix this by analyzing the evidence. Where did the support come
from? Is there self interest involved? Did you get the whole picture?
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7. Faulty Causal Relationship�(also called Post Hoc)
• Def. To excuse an action or belief by making it sound sensible. Often this assumes that anything that came before an event caused it to happen.
• Example: – I stole the towel from the hotel. They expect people to take
them. – Eating 5 energy bars and drinking 2 Cokes helps me get better
grades. I did this and got an A on my history test. Fix this by examining the relationship between ideas. Make sure the facts precede the theory and the reasons
precede and cause the belief.
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8. Misleading Comparison • Def. Mistakenly believing that two
situations or people can be compared. • Examples:
– Jill looks good in red. I’ll buy red pants, too. – Forcing students to read books is like herding
cattle to slaughter. – You gave him extra time on the test, so I should
get extra time too. – Saddam Hussien is Hitler.
Fix this by remembering that every person and situation has different circumstances.
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9. Bandwagon
• Def. Lots of people do this, so you should, too.
• Examples: – Adults are smoking, so it is ok to do so. – The American people do not stand for . . .
Fix this by making decisions based on facts, not popularity.