Logical Reasoning Flashcards
Premise Indicators
F-BAGS (for, because, as, given that, since)
Conclusion Indicators
A-SCHITT (accordingly, so, consequently, hence, it follows that, therefore, thus)
Classic Flaw 1: Bad conditional reasoning
Loophole: What if we actually have to follow the rules of conditional reasoning?
There are conditional premises and a crazy person reads them incorrectly (e.g. concludes by reading conditions backwards w/o negating, or concludes by negating conditions and reading it forwards).
Example: If you are awake, you will eat peanut butter (PB). All PB eaters love cherries.
Flaw: Therefore, if you love cherries, you must be awake
Classic Flaw #2: Bad Causal Reasoning
Loophole: What if one of the Omitted Options is the case?
Crazy person sees that two things are correlated and concludes that one of those things is causing the other.
Example: If Obi is awake, he will eat peanut butter (PB). Obi is awake. Flawed conclusion: Therefore, Obi’s awakening caused the downfall of the jelly industry.
Loophole 1: what if some other new factor caused Jelly’s downfall?
Loophole 2: what if the downfall of the jelly industry caused Obi to wake up from his sleep?
Loophole 3: what if Obi’s sleep schedule and/or PB preference has no impact on the global sales of jelly?
Classic Flaw #3: Parts don’t equal wholes
Loophole: What if wholes don’t necessarily equal parts?
Crazy person says that a member of a category has a property, and concludes that the category itself also has that property. OR they say a category has a property, and concludes that a member of that category also has that property.
Example: Obi sees a peanut butter pie on the table and cuts a slice (a vaguely triangular shape). He turns to you and says this piece of pie has a circular shape because the whole pie is circular. You would no longer be his friend.
Example 2: Obi tells you that because his piece of pie is triangular then the whole pie is triangular. You would no longer be his friend.
Class Flaw 4: Overgeneralization (Parts don’t equal all the parts)
Loophole: What if we can’t generalize from this one thing to a bunch of other things?
Crazy person talks about something having a property, then concludes that a bunch of other things also have that property. Loophole: what if we can’t generalize from this one thing to a bunch of other things?
Example: Obi’s PB&J sandwich tasted like orange juice. Therefore, all PB&J sandwiches taste like orange juice.
Classic Flaw #5: Survey Problems
Loophole: What if the sample was biased, questions were biased, there are other contradictory surveys, people lie on surveys, or the sample is too small?
A crazy person concludes things based on a survey but there are many things wrong with it:
biased sample: Obi conducts a survey of America’s favorite snack and only asks politicians, an unrepresentative group
biased question: Obi conducts a survey and crafts his questions to get a certain response (“good people love peanut butter. Do you love peanut butter?”)
survey liars: Obi’s wife is an FBI agent looking to arrest anyone who doesn’t like peanut butter, giving respondents a reason to lie. There doesn’t need to be a specific incentive to lie.
small sample size: Obi only asks 5 people for their favorite snack
contradictory survey: Obi’s survey said 70% love PB, but a different survey shows only 5% do
Classic flaw #6: False uniformity
Loophole: What if the two groups were different in a key respect?
The two groups are always inconveniently different. Crazy researcher assuming two groups are the same in all respects except the ones called out as part of the study.
Example: Obi forms two groups, A (people 4 ft or shorter) and B (people taller than 4 ft). His research determines Group A loves PB and Group B doesn’t, therefore height is a factor in PB preferences.
Classic Flaw #7: Possibility does not equal Certainty
Loophole: What if lack of evidence doesn’t equal evidence of lacking? Or what if proof of evidence doesn’t equal evidence of proof?
Facts are not affected by the failure of an argument. Both of these are flaws:
A) It’s not necessarily true, so it cannot be true
B) It could be true, so it must be true
Example: It hasn’t been proven that Obi hates jelly. Obi talks crap about jelly very often. Thus, Obi hates jelly.
Example 2: Some people overheard Obi saying he will never eat jelly again. Thus, Obi must hate jelly
Classic flaw #8: Implication
Loophole: What if the person in question isn’t aware of what their belief implies?
A has a belief. Crazy person mentions a factual implication of that belief. Crazy person claims that A believes the implication of the belief.
Example: Obi believed that PB can control minds. PB always wears shoes. Therefore, Obi believes a shoe-wearer can control minds.
Other examples, don’t assume Obi is aware of rules (no matter how factual they are or how related they are to what he actually believes in). It must be explicitly states that he is aware of those other factual implications
Classic flaw #9: False Dichotomy
Loophole: What if there are more than just two options?
Crazy person outlines two options; then eliminates one option and concludes the second option must be the case. But there could be more options.
Two ways false dichotomies go wrong: limiting options: Obi is a vegetarian so he will not have steak for lunch. It follows that he will have peanut butter instead.
Or limiting a spectrum (up, down, unchanged): The quality of the peanut butter did not deteriorate overnight, so it must have improved
Classic flaw #10: Straw Man
Loophole: What if what they said has nothing to do with the claim they’re pretending to respond to?
Sane person makes a claim. Crazy person responds to an entirely different claim, but pretends they responded to the sane person.
Obi: I really love peanut butter
Crazy person: So what you’re really saying is you hate jelly. How dare you!
Classic flaw #11: Ad Hominem (insulting people; “to the person”)
Loophole: What if this person’s character/motivation doesn’t affect the truth?
Sane person makes a claim. Crazy person talks about how the sane person is somehow awful. Crazy person then concludes that the sane person’s claim is false.
Proponents don’t affect the truth/falsity of their position.
Example: Obi says that PB is delicious, but Obi works for the PB lobby. So PN is not delicious.
Classic flaw #12: Circular Reasoning
Loophole: What if we can’t use the conclusion as evidence for itself?
Crazy person concludes something. Crazy person supplies premises that assumes the conclusion is already true. A circular argument assume the conclusion is true before doing the work of proving it so.
Example: Obi’s love for peanut butter will ruin society. He may try to love jelly, but his love for peanut butter, which will really be disastrous for society, is too strong.
Classic flaw #13: Equivocation
Loophole: What if we shouldn’t let words change in meaning?
Crazy person uses a word or idea, intending one of its possible meanings; then concludes something using the other possible meaning.
Example: Obi loves really rich peanut butter. He loves all the many flavors. Thus we can expect him to choose the most expensive PB.
Classic flaw #14: Appeal Fallacies (opinion does not equal evidence of fact)
Loophole: What if this opinion doesn’t equal evidence of fact?
Crazy person says that a person or group believes something; then concludes that thing must be true. Two ways:
Using a non-expert opinion to support their conclusion: Obi says peanuts grow in deserts (not valid because Obi is not a peanut expert)
Using public opinion to support conclusion: 50% of Americans love the taste of peanut butter, so peanut butter must be delicious (a high percentage of random people believing anything has very little bearing on whether that thing is actually true).
Classic flaw #15: Irrelevant!
Loophole: What if the premises and the conclusion have nothing to do with one another?
Crazy person supplies a few premises; then concludes something that is unraveling to those premises.
Example: I hate jelly. Jelly was created in the 1600s. Jelly has a long history of being purple.
Classic flaw #16: Percentages don’t equal Numbers
Loophole: What if the group size doesn’t stay the same?
These arguments purposefully leave out that group size could CHANGE, which would make the conclusions invalid
Crazy person says that a % went up, then concludes the associated real number went up/down
OR
Crazy person says that a real number went up, then concludes the associated % went up/down
Example: Obi sold 1,000 more PB jars today than he did yesterday. Therefore his share of the market must have risen considerably (this argument ignores overall group size of the market)
CLIR
Controversy — Debate (“whether” + second speaker’s inference)
Loophole — Argument (“what if…” possibility that destroys conclusion)
Inference — Premise Set (a valid conclusion not explicitly stated)
Resolution — Paradox (“premise 1, but Resolution, so Premise 2”)
If Family
S-PIEEWAA:
Sufficient People who In order to Each Every(time) When(ever) Any(time) All
Then Family
N-MORPHED:
Necessary Must Only (if) Requires Precondition Have to Essential Depends
- Some Family
- Most Family
- The only valid inferences for some and most
Some and Most are rogue sufficients that go right before their targets.
Some Family: FAMS (Few, At least one, Many, Several)
Most Family: PUMM (Probably, usually, mostly, more often than not)
Reverse of Most is Some: otters -m->burglars = burglarsottets
Only valid inferences:
A ↔️B —>C…then A↔️C
A -m-> B —>C…then A -m->C
A-m->B and A -m->C…then B↔️C
[If and Only If] formula and family
Family: BAWI (but not otherwise, all and only, when and only when, If but only if)
C↔️F
[Unless] formula and family
Unless Family: WUE (without, until, except)
=
~[way things are]—>Exception
[Either + Or] formula
Negate half and place in sufficient:
~P —> D
[No, None, Nobody, Never] formula
Create if/then and negate the necessary side:
A—>~B
Power Players?
Must, Cannot
Could, Not necessarily
What are loopholes really?
Negated necessary assumptions!
Types of Loopholes
- Dangling variables: new words that appear in the conclusion and not in the premises (Loophole: what if those two things are not necessarily the same?)
- Secret value judgments: when the author makes a judgment (morality, appropriateness, prudent/imprudent, should/shouldn’t, etc) (Loophole: what if that value judgment doesn’t have that definition?)
- Secret Downsides: author compares two things and says one is superior without giving you the full story. (Loophole: what if the argument’s preferred option has a big downside?)
- Assumed Universal Goals: things author assumes everyone would want (e.g. losing weight, lowering cholesterol, making more money, being more successful, being healthier) (Loophole: what if they don’t want to [assumed universal goal]?)
- 16 classic flaws
- Negated necessary assumptions
Powerful - Provable
Powerful: SW SCCER (Strengthen, Weaken, SA, Counter, Contradiction, Evaluate, Resolution)
Everything else is Provable
Question Type: Strengthen
Give correct answer, back-up plan, and question stem keywords
Correct answer: The most powerful thing you can find to help the argument’s conclusion
Back-up Plan: Does this make the conclusion more likely to be true?
Question Stem Keywords: strengthen, most helps to + justify/strengthen/support
Question Type: Weaken
Give correct answer, back-up plan, and question stem keywords
Correct Answer: The most powerful answer that destroys the argument’s conclusion
Back-up plan: Does this make the conclusion less likely to be true?
Question stem keywords: weaken, most undermines the conclusion, undermine the argument, most vulnerable, count as evidence against, calls into question
Question Type: Sufficient Assumption
Give correct answer, back-up plan, and question stem keywords
Correct Answer: The most powerful answer that proves the conclusion 100% valid
Back-Up plan: If this powerful shit is true, is the argument 100% valid?
Question Stem Keywords: enable the conclusion to be properly drawn, the conclusion follows logically if, justify the conclusion
Question Type: Counter
Give correct answer, back-up plan, and question stem keywords
Correct Answer: The most powerful answer the 1st speaker could say to destroy the 2nd speaker’s controversy
Back-Up plan: Would the 1st speaker say this and does it hurt the 2nd speaker’s argument?
Question Stem keywords: counter, in response to
Question Type: Contradiction
Give correct answer, back-up plan, and question stem keywords
Correct Answer: The most powerful answer that contradicts literal words from the stimulus
Back-Up plan: Does this + stimulus = a Paradox?
Question stem keywords: cannot be true, violates the principle, could be true EXCEPT
Question Type: Evaluate
Give correct answer, back-up plan, and question stem keywords
Correct Answer: Most powerful answer that zeroes in on a Loophole
Back-Up Plan: Is this crucial for the argument’s validity?
Question stem keywords: evaluate the argument, most helpful to know, relevant to evaluating
Question Type: Resolution
Give correct answer, back-up plan, and question stem keywords
Correct Answer: The most powerful to resolve the paradox
Back-Up plan: Does this make the Paradox make sense?
Question stem keywords: most helps to + explain / resolve / account for, discrepancy, paradox, surprising result
