Classic Flaws in Logical Reasoning

Question 1

Bad Conditional Reasoning

Answer 1

-author concludes something by misreading the conditional premises by either: 1) reading the conditional premises backwards without negating or 2) negating the conditional premises and reading it forwards (we can’t assume anything with the presence of necessary condition).

Loophole: What if we actually had to follow the rules of conditional reasoning?

Question 2

Bad Causal Reasoning

Answer 2

-author sees that 2 things are related then concludes that one of those things is causing the other

Loophole: What if one of the omitted options is the case?

1. no relationship
2. new factor
3. causation is backwards

Question 3

Whole-to-Part & Part-to-Whole

Answer 3

-author says the premise has all the parts of something having a property then concludes that the whole also has that property.

Loophole: What if wholes don’t necessarily equal parts?

Question 4

Overgeneralization

Answer 4

-takes something small and concludes something big; assumes that a part = all the parts

Loophole: What if we can’t generalize from this one thing to a bunch of other things

Question 5

Survey Problems

Answer 5

-always assume surveys are done with greatest incompetence

UNLESS the stimulus explicitly accounts for survey error, the Loophole is: What if the sample was biased, the questions were biased, there are other contradictory surveys, or the sample is too small?

Question 6

False Starts

Answer 6

-assumes that the two groups are the same in all respects except the ones called out on the study

Loophole: What if the two groups were different in a key respect?

Question 7

Possibility ≠ Certainty

Answer 7

Absence of Evidence ≠ Evidence of Absence: It’s NOT NECESSARILY TRUE, so it CANNOT BE TRUE.

Proof of Evidence ≠ Evidence of Proof: It COULD BE TRUE, so it MUST BE TRUE.

Loopholes: What if absence of evidence ≠ evidence of absence? What if proof of evidence ≠ evidence of proof?

Question 8

Implication

Answer 8

-Someone has a belief , crazy person mentions a factual implication of that belief, and crazy person claims that someone believes the implication of that belief.

Loophole: What if the person in question isn’t aware of what their belief implies?

Question 9

False Dichotomy

Answer 9

pretends there are only two options when there could really be more

2 classes of false dichotomy: Limiting a spectrum and Limiting options

Loophole: What if there are more than just two options ?

Question 10

Limiting a spectrum (false dichotomy)

Answer 10

On a spectrum, you can go up, go down, or stay the same. Spectrum-limiting authors will pretend there are only two options, when there are really three: up, down, or unchanges.

NOT MORE ≠ LESS: Assumes if it’s not going up, it MUST go down
NOT LESS ≠ MORE

Question 11

Limiting options (false dichotomy)

Answer 11

-pretends there are only two options when there could be more (which is trickier than limiting a spectrum)

Because Raoul is a vegetarian, he WILL NOT HAVE THE PEPPERONI pizza for lunch. It follows that he WILL HAVE THE CHEESE pizza.

In the example, the author limited options by assuming there are only cheese and pepperoni pizzas in the world.

Question 12

Straw Man

Answer 12

Sane person makes a claim. Crazy person responds to an entirely different claim, but pretends they responded to the sane person. In reality, crazy person distorts what their proponent said to make the sane person’s claims easier to take down.

Loophole: What if what they said has nothing to do with the claim they’re pretending to respond to?

Question 13

Ad Hominem

Answer 13

Ad hominem premises insult the proponent of a position, but then the concludes that the proponent’s claim is false.

Loophole: What if this person’s character/motivation doesn’t affect the truth?
(Bad proponent ≠ Bad argument)

Question 14

Circular Reasoning

Answer 14

• author concludes something and gives premises that assume the conclusion is true before doing the work of proving it.
• often, circular arguments say an objections to the conclusion must not be true because the objection disproves the conclusion, assuming there’s NO WAY this conclusion can be wrong.
• approach: look for synonyms and similar concepts explained using different words

Loophole: What if we can’t use the conclusion as evidence for itself?

Question 15

Equivocation

Answer 15

When the author changes the meaning of a word throughout an argument (dangling variable)

Loophole: What if we shouldn’t let words change in meaning?

Question 16

Appeal Fallacies

Answer 16

Appeal fallacies turn someone’s opinion into a fact by :

1) invalid appeal to authority
2) invalid appeal to public opinion

Question 17

Invalid appeal to authority (appeal fallacies)

Answer 17

happens when the author uses a non-expert opinion to support their conclusions

Question 18

Invalid appeal to public opinion (appeal fallacies)

Answer 18

appeals to public opinion are invalid because people are unreliable. A high percentage of random people believing anything has very little bearing on whether that thing is actually true.

Loophole: What if this opinion ≠ evidence of fact?

Question 19

Irrelevant!

Answer 19

Irrelevant! happens when the premises are entirely unrelated to the conclusion.

Loophole: What if the premises and the conclusion have nothing to do with one another?

Question 20

Percentages ≠ Numbers

Answer 20

-Premises about numbers almost never lead to conclusions about percentages and vice versa

Loophole: What if the group size doesn’t remain the same?

Question 21

Why rising percentage doesn’t necessarily imply a rising number and vice versa?

Answer 21

Whenever an argument mentions percentages and numbers, they’re purposefully not mentioning the group size. This is bad because the conclusion only works when the overall group size is just right.

Question 22

Dangling Variable

Answer 22

• most common error in LR
• new words that appear in the conclusion and not in the premises

Loophole: What if those two things aren’t necessarily the same?
i.e. put a ≠ between the two things that the author pretends are the same.

Question 23

Conditional Dangling Variables

Answer 23

-adds a new variable to the conclusion’s conditional statement
Loophole: What if you can’t stealth add new variable to the end of conditional chain?

Question 24

Secret Value Judgments

Answer 24

when the author gets judgy in the conclusion

• authors can’t just deem something “moral” or “appropriate” in the conclusion without defining what the words imply in the premises
• loophole reminds the authors that they can’t just assume a convenient definition for these words

Loophole: What if that [value judgment] doesn’t have that [definition]?

Question 25

Secret Downsides

Answer 25

-happens when the author compares two things and says one of them is superior without giving the full story. They’ll say their preferred choice has a few upsides, but your loophole will remind them of the Secret Downside they aren’t considering.

Loophole: What if the argument’s preferred option has a big downside?

Question 26

Assumed Universal Goals

Answer 26

things that the author assumes everyone would want

Loophole: What if they don’t want to [assumed universal goal]?

Question 27

Cause and Effect (Causal reasoning)

Answer 27

-claims that cause & effect relationship exists
Loophole (3 classes of omitted options)
1. no relationship
2. backwards causation
3. new factor causing one or both

Question 28

Correlation & Causation

Answer 28

Correlation ≠ Causation
When two things are correlated with one another, there are four possible explanations for that occurrence: 
1. Cherry-picked causal explanation
2. Backwards causation
3. New factor causing one or both
4. No relationship

-Causal conclusions are cherry-pickers because none of the four possible explanations are inherently more likely than the other.

Question 29

Sufficient assumption test

Answer 29

Does [assumption candidate] prove the [conclusion]?

If yes- then it is sufficient assumption

Question 30

Necessary assumption test

Answer 30

If the conclusion is true, must [assumption candidate] be true?
If yes- this is a necessary assumption

Question 31

Assumption chain

Answer 31

Sufficient assumption –> Conclusion true –> Necessary assumption

Question 32

Premise indicators

Answer 32

because
for
since
as 
given that

Question 33

Conclusion indicators

Answer 33

therefore
thus
accordingly
hence
consequently
it follows that
so

Question 34

Designing loopholes for arguments

Answer 34

1. ID conclusion

2. Say “this conclusion isn’t necessarily true”, what if….. [design possibility that destroys the conclusion]

Question 35

Designing loopholes for premise sets

Answer 35

1. design an inference that sticks to exact words of stimulus

Question 36

Designing loopholes for debates

Answer 36

• design a controversy around what the 2 speakers are disagreeing over
  1. Take an inference from 2nd speaker’s statements
  2. Stick a “whether” in front of the inference

Question 37

Designing loopholes for paradox sets

Answer 37

• contradicting premises

- design loophole resolution: What would make this all make sense?