Logical Reasoning Flashcards
How do you form a contrapositive statement?
Take the original relationship, flip it and then negate both terms
What does the negative of X mean?
Not X
What are the Group 1 sufficient indicators?
- If
- All
- When
- Whenever
- Every
- Anyone
- Where
- Any/the only
What are the Group 2 necessary indicators?
- Only/only ____
- Always
- Requires
- Must
- Necessitates
What are the Group 3 indicators and how do you handle them?
Pick one of the components, negate it and make it the sufficient condition
- Unless
- Until
- Without
What are the Group 4 indicators and how do you handle them?
Same as Group 3, but make it the necessary condition
- No
- None
- Never
- Cannot
- Not both
How do you weaken an argument?
Concede the premises and show that the conclusion does not follow (DON’T ATTACK PREMISES)
Do you accept the premises/conclusion or the answers with MSS questions?
The premises/conclusion
Do you accept the premises/conclusion or the answers with Weakening questions?
The answers
How do you handle strengthening questions?
Find gap between premise/conclusion and try to bolster it
How do you handle MBT questions?
- Ask if the conclusion must be true
- Ask if you could say “not necessarily” (don’t fall for could be true)
What should you do if the author’s scope/claims are broad and general?
Avoid answers that are specific or absolute
Watch out for exaggerations (like going from “some” in the stimulus to “most” in the answer choices)
Ok
What will correct answers usually offer in MBT questions?
- Restate the stimulus (watch out for exaggerations/slight manipulations)
or
- Result from combining two elements from the stimulus
What’s the biggest logical trap you need to avoid?
Sufficient/Necessary swap
What is true about correct answers for MBT?
They can always be proven by the stimulus
What are some common question stems for MBT?
…which of the following must also be true? …which of the following can be properly inferred? …most strongly support which of the following?
What types of answers should you avoid in MBT?
- Could be true
- Exaggerated
- New information
What types of incorrect answers appear for MP?
- Answers that are true, but don’t encapsulate the point
- Answers that repeat premises
What does the word “some” mean?
At least one, possibly all
What does the word “most” mean?
A majority, possibly all
Do contrapositives exist for “most” or “some” statements?
No
Which logical indicators DO NOT have reversible relationships?
All or most
Which logical indicators do have reversible relationships?
None, some, if-but-only-if
What is the square-rectangle of most, all, and some?
All → Most → Some
What is the negative square-rectangle?
None → Most are not → Some are not
What is a sufficient condition?
An event or circumstance whose occurrence indicates that a necessary condition must also occur.
What is a necessary condition?
A necessary condition can be defined as an event or circumstance whose occurrence is required in order for a sufficient condition to occur.
What is the relationship between sufficient and necessary conditions?
If a sufficient condition occurs, you know that a necessary condition also occurs
What logical issue should you watch out for?
Mistaken reversal (of the sufficient and necessary conditions)
What phrases often introduce a sufficient condition?
- If
- When
- Whenever
- Every
- Any
- All
- People who
- In order to
What phrases often introduce a necessary condition?
- Then
- Only
- Only if
- Must
- Required
- Unless
- Except
- Until
- Without
How should you handle Weaken questions?
- Focus on the conclusion
- Suspect information in the stimulus
- New information is fine in Weaken questions
What phrases often introduce Weaken questions?
- Weaken
- Attack
- Undermine
- Refute
- Argue against
- Call into question
- Cast doubt
- Challenge
- Damage
- Counter
What should you be looking for in Weakening questions?
- Incomplete information
- Improper comparisons
- Qualified conclusions
If a stimulus is particularly difficult, beware answer choice A
Ok
How do you attack a causal conclusion?
- Find an alternate cause for the effect
- Show that when the cause happens, the effect does not follow
- Show that the effect can occur w/o the cause being present
- Show reverse causality
- Show the statistics used are questionable
For Strengthen, Justify the Conclusion, and Assumption questions: what part of the stimulus should you focus on?
The conclusion
What will the correct answer choice for a Strengthen question do?
Strengthen the argument by 1-100%
What will the correct answer for a Justify the Conclusion question do?
Prove it 100%
What will the correct answer for an Assumption question do?
Show what must be true for the argument to be true
What must correct answers for assumption questions do?
Make a statement that the author relies upon/is fully committed to
What is the logical opposite of “all”?
Not all
What is the logical opposite of “some”?
None
What are three quirks of Assumption questions?
- Choices that start w/ “at least one” or “at least some” have an unusually high chance of being correct
- Avoid answers that claim a point was the most important consideration
- Watch out for “not” or other negatives in the answer choice
- Avoid answers that describe a cause of the cause or effect of the effect
