Chapter 6: Logical Fallacies II §

(F) Day of the week: Tuesday Class: IS209 Created Time: June 2, 2020 11:29 AM Database: Class Notes Database Date: June 2, 2020 11:29 AM Days Till Date: Passed Last Edited Time: June 9, 2021 10:39 AM Type: Lecture

I. Fallacies of Insufficient Evidence §

Fallacies of Insufficient Evidence is relevant to the conclusion but does not provide enough evidence to prove the conclusion true.

1. Inappropriate Appeal to Authority §

When an arguer cites a witness or authority that is unreliable.

• Authority on Different Field: citing someone’s expertise on field A to prove an argument in field B
• Biased Source: citing someone with obvious bias or motive to mislead.
• Accuracy of Source’s Experience: citing someone with reasonably inaccurate observations or experience
• Generally Unreliable Source: citing someone/thing that is generally known as unreliable.
• Incorrectly Cited Source: mistakenly citing information that was wrongly interpreted or taken out of context.
• Expert Conflicted Claim: to cite someone who argue against the general experts
• Experts on Controversial Issues: controversial issues of opinion cannot be proven by experts
• Improbable Claim: citing someone reliable but the claim is so hard to believe and need additional evidence.

2. Appeal to Ignorance §

occurs when an arguer assert that a claim must be true because no one has proven it false or visa versa.

• When you don’t have enough evidence to prove your point

(Exception)

• If the conclusion must be one or the other, and it has been thoroughly proven it cant be one, therefore it must be the other.

  • Example
    • We’ve searched this car from top to bottom looking for the stolen jewels, and no trace of them has been found. Therefore, probably the jewels aren’t in the car.
    • After years of extensive scientifi c testing, there is no evidence that substance XYZ is toxic to rodents. Therefore, it’s reasonable to conclude that substance XYZ is not toxic to rodents

• When a special rule exist where a claim is rejected unless a certain amount of proof is met

  “Innocent until proven guilty”: false until proven true

3. False Alternatives §

giving the choice of two/several extreme to prove one extreme is more preferable. When there are other less extreme choices available.

Forms

• If, Then: condition outcome

  If we don’t elect a Democrat as president, then the economy will go down the tubes. Obviously, we don’t want the economy to go down the tubes. So, we should elect a Democrat as president.

• Either or: agree with one or the other

  Either we elect a Republican as president, or crime rates will skyrocket. Obviously, we don’t want crime rates to skyrocket. Therefore, we should elect a Republican as president

4. Loaded Question §

When an arguer ask a question that contains an unfair assumption that traps you at fault with any answer

Joe: Have you stopped cheating on exams?

Pete: No!

Alternative

Question 1: Did you cheat on exams in the past?

Question 2: If you did cheat on exams in the past, have you stopped now?

5. Questionable Cause §

Post Hoc Fallacy: When an arguer claims one thing is the cause of something else without sufficient evidence.

a. Mere Correlation Fallacy §

Saying A and B happened together accidentally, an arguer concludes A must have caused B or visa versa

b. Oversimplified Cause Fallacy §

Saying A is the sole cause of B, while B has many other causes

6. Hasty Generalization §

drawing a general conclusion from a biased or too small sample size.

7. Slippery Slope §

Saying a harmless action that will domino effect into disasterous outcome without sufficient evidence it’s certainly so.

Pattern:

1. The arguer claims that if a certain seemingly harmless action, A, is permitted, A will lead to B, B will lead to C, and so on to D.
2. The arguer holds that D is a terrible thing and therefore should not be permitted.
3. In fact, there is no good reason to believe that A will actually lead to D.

(Exception)

Saying that the seemingly harmless action can lead to a very disasterous that it’s reasonable and worth it to avoid this action.

8. Weak Analogy §

“That’s like comparing Apples and Oranges”

When an arguer compares two or more things which are not similar or comparable.

Common Pattern: §

The basic pattern here is

1. A has characteristics w, x, y, and z.
2. B has characteristics w, x, and y.
3. Therefore, B probably has characteristic z too.

• Example:

  Alan is tall, dark, and handsome and has blue eyes. Bill is also tall, dark, and handsome. Therefore, Bill probably has blue eyes, too.

(Exception)

• When the similar characteristics are justifiable to think their similar in other ways

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1. A is an x, and A is a y.

2. B is an x, and B is a y.

3. C is an x, and C is a y.

4. D is an x.

5. Therefore, D is probably a y too.

(Exception)

• When the things being compared are, in fact, relevantly similar.

---

When an arguer simply asserts, without further elaboration, that two cases are relevantly similar.

1. list all important similarities between the two cases
2. list all important dissimilarities between the two cases
3. decide whether, on balance, the similarities are strong enough to support the conclusion

9. Inconsistency §

Arguer assert contradictory statements

• Example: Yogi Berra: That place is old news. Nobody goes there anymore. It’s too crowded. 16