LSAT - Logical Reasoning

P - Premise, MC - Main Conclusion, AC - Answer Choice, MBT - Must Be True

Sufficient Assumption (SA)

1. Identify the premise/Main Conclusion

2. Spot the gap: Why am I not believing this MC given the P’s?

3. Prephrase: What’s an added fact or rule that fill the gap & 100% guarantees the MC?

4. 2 Tests on AC’s:

   1. Does this apply to the premises?

   2. Does it guarantee the MC?

Flaw

1. Identify the premise (P)/Main Conclusion (MC)

2. Spot the gap: Why am I not believing this MC given the P’s?

3. Keep an open mind & evaluate AC’s with 2 tests:

   1. TRUE? Is this AC entirely accurate about the stimulus?

   2. FLAW? Is this invalid reasoning objectively? Or is it fine that the argument does this?

AKA: Invalid arguments! The conclusion is not fully supported by the premises!

Necessary Assumption (NA)

1. Identify the premise (P)/Main Conclusion (MC)

2. Spot the gap: Why am I not believing this MC given the P’s?

3. Prephrase: What must be assumed if my MC really does follow from the P’s?

4. 2 tests on AC’s:

   1. MBT? If the MC really does follow given these P’s, does this AC have to be true?

   2. Negate & Destroy? If I were to assume this AC is NOT actually true, would it destroy the link between P/MC?

Strengthen

1. Identify the premise (P)/Main Conclusion (MC)

2. Spot the gap: Why am I not believing this MC given the P’s?

3. Prephrase: What’s an example of an added fact (premise) that would make my MC more believable given these P’s?

4. Keep an open mind & evaluate AC’s. Does this, if I assume it to be true, make my MC more likely to be true (by even 1%)?

Pseudo-Sufficient Assumption (PSAr) - FIND THE RULE

1. Identify the premise (P)/Main Conclusion (MC)

2. Spot the gap: Why am I not believing this MC given the P’s?

3. Prephrase: What rule does it seem like they’re following to get from P to MC?

4. 2 tests on AC’s:

   1. Does this apply to the premises?

   2. Does it basically guarantee the MC?

      • More wiggle room for an AC to be imperfect/more general than expected!

Weaken

1. Identify the premise (P)/Main Conclusion (MC)

2. Spot the gap: Why am I not believing this MC given the P’s?

3. Prephrase: What’s an example of an added fact (premise) that would make my MC even less believable?

4. Keep an open mind & evaluate AC’s:

   • Does this, if I assume it to be true, make my MC less likely to be true (by even 1%)?

Parallel Flaw

1. Identify the premise (P)/Main Conclusion (MC)

2. Spot the gap: Why am I not believing this MC given the P’s?

   • If conditional reasoning - Diagram ASAP

3. Choose the AC that matches the flaw.

   • Order, topic, and structure (unless it’s conditional reasoning) don’t matter!

Evaluate

1. Identify the premise (P)/Main Conclusion (MC)

2. Spot the gap: Why am I not believing this MC given the P’s?

3. Prephrase: What question when answered would tell me if my MC really is true given these premises?

4. AC’s take the form of questions/whether-or-not’s

   • Give a hypothetical answer to each & choose the one that tells you whether this argument is valid!

Parallel Method of Reasoning

1. Identify the premises/main conclusion - (likely to NOT be flawed, aka no gap/hole, but COULD)

   • If conditional reasoning - Diagram ASAP!

2. Choose the AC that matches the structure - Order & topic DON’T MATTER

   • First, match conclusion type - Predict? If/Then? Recommend? Likelihood?

Main Conclusion (MC)

1. ID main conclusion with 2 tests:

   • WHY? Can I point to a reason to believe this in the stimulus?

   • SC therefore MC - to pit two potential MC’s against each other, ask if knowing one of them gives more reason to believe the other

2. Pick the AC that’s both stated/rephrased in the stimulus & receives but does not lend support

Resolve, Reconcile, Explain (RRE)

1. Put the paradox/mystery in the stimulus into your own words.

2. Prephrase: What fact/hypothesis would make it make sense?

3. Open mind to evaluate AC’s:

   • If this were true, does it explain both sides of the paradox?

   • Eliminate if it leaves you more confused/explains just half.

Argument Part (AP)

1. Highlight the claim in question in the stimulus

2. Read entire stimulus for structure: ID premises/conclusions

3. Prephrase: Is this claim a premise, sub or main conclusion or something else (Concession, OPA, context)

4. Choose the AC that is 100% descriptively accurate!

Most Strongly Supported/Inference (MSS/Inf)

1. Understand the stimulus in your own words as a string of facts - Not necessarily P/MC structured!

   • Diagram ASAP if conditional reasoning (less common)

   • Chain diagrams!

2. Open mind & evaluate AC’s

   • 4 will be could-be-true’s or must-be-falses (eliminate those)

   • 1 will be more supported by the stimulus than the others! Does not have to be MBT, but could be!

HINT: Weaker, open-ended wording is easier to support!

Must Be True (MBT)

1. Understand the stimulus in your own words as a string of facts - Not necessarily P/MC structured!

   • Diagram ASAP if conditional reasoning (very common)

   • Chain diagrams!

2. Open mind & evaluate AC’s

   • 4 will be could-be-true’s or must-be-falses (eliminate those)

   • 1 will be 100% guaranteed to be true given the stimulus! CHOOSE IT!

Must Be False (MBF)

1. Understand the stimulus in your own words as a string of facts - Not necessarily P/MC structured!

   • Diagram ASAP if conditional reasoning (very common)

   • Chain diagrams!

2. Open mind & evaluate AC’s

   • 4 will be could-be-true’s (Ex. Mistaken reversals or must-be-trues (eliminate those)

   • 1 will be 100% guaranteed False!

HINT: Almost every MBF takes an if A → B → C chain & says if A → B (not B) (AKA denies the necessary)

Pseudo-Sufficient Assumption (Apply the Rule) aka Simon Says (PSAa)

1. Put the principle/rule in the stimulus into your own words

   • If conditional reasoning, diagram ASAP!

2. Only necessaries (on the right side of diagrams) can be guaranteed.

   • Do a first pass at AC’s & eliminate anything that makes a judgement call that cannot be guaranteed

3. Of the remaining 2-3 AC’s, choose the one that does exactly as the rule (Simon) says! (triggers the right sufficient condition(s)).

Method of Reasoning (MoR/Method)

1. Identify premises/main conclusion

2. Prephrase: How does the author make their way from P to MC?

   • Ex. Disprove someon’s P/MC/Assumption, analogy, counterexamples, generalization, principle, support, etc…)

3. Open mind & evaluate AC’s:

   • 4 are inaccurate, only 1 is 100% descriptively accurate (pause every few words & map it back onto the stimulus)

Agree/Disagree

1. ID premises & main conclusion for speaker 1 first

2. Do a first pass at AC’s & eliminate any that speaker 1 does NOT take a stance on

3. ID P/MC for Speaker 2

4. Agree/Disagree

   • Agree - Choose the AC they both would say YES to

   • Disagree - Choose the AC that 1 person would say yes to & the other would say no

HINT: Use a T-chart to organize ACs:

Question types with a gap/hole in the stimulus

Sufficient Assumption (SA), Necessary Assumption (NA), Flaw, Weaken, Strengthen, Psuedo-Sufficient Assumption (Find the Rule, PSAr), Parallel Flaw, Evaluate, Parallel Method of Reasoning.

AC Tests for SA questions

1. Does this apply to the premises?

2. Does it guarantee the MC?

AC Tests for Flaw Questions

1. TRUE? Is this AC entirely accurate about stimulus?

2. FLAW? Is this invalid reasoning objectively? Or is it fine that the argument does this?

AC Tests for NA Questions

1. MBT? If the MC really does follow given these P’s, does this AC have to be true?

2. Negate & Destroy? If I were to assume this AC is not actually true, would it destroy the link between P/MC?

AC Test for Strengthen Questions

Keep an open mind & evaluate AC’s: Does this, if I assume it to be true, make my MC more likely to be true (by even 1%)?

AC Tests for Psuedo-Sufficient Assumption (Find the Rule) Questions

1. Does this apply to the premises?

2. Does it basically guarantee the MC? More wiggle room for the AC to be imperfect/more general than expected!

AC Tests for Weaken Questions

1. Keep an open mind & evaluate ACs: Does this, if I assume it to be true, make my MC less likely to be true (by even 1%)?

AC Format for Evaluate Questions

AC’s take the form of questions/whether-or-nots - give a hypothetical answer to each & choose the one that tells you whether the argument is valid!

AC tactic for Parallel Method of Reasoning Questions

Choose the AC that matches the structure (First, match conclusion type - Predict? If/Then? Recommend? Likelihood?

• Order & Topic do not matter

Eliminate wrong AC tactic for Parallel Method of Reasoning Questions

Eliminate any AC’s whose conclusion types do not match the structure of the stimulus’ MC.

• Predict

• If/Then

• Recommend

• Likelihood

AC Test for MC questions

Pick the AC that’s both stated/rephrased in the stimulus & receives but does not lend support!

AC Test for Resolve, Reconcile, Explain Questions

If AC were true, does it explain both sides of the paradox? Eliminate if it leaves your more confused/explains just half.

AC Type for Most Strongly Supported/Inference Questions

AC will be the closest AC to MBT. The others will be could-be-trues or must-be-falses.

AC Type for MBT Questions

1 will be guaranteed to be true given the stimulus.

AC Type for MBF Questions

1 will be 100% guaranteed False!

Almost every MBF takes an if A → B → C chain and says if A → B (not B), aka denies the necessary

AC Type for Psuedo-Sufficient Assumption (Apply the Rule aka Simon Says) (PSAa) Questions

AC will do exactly as the rule (Simon) says (triggers the right sufficient condition(s))

Prephrase tactic for Method of Reasoning (MoR/Method) Questions

How does the author make their way from P to MC?

Ex. Disprove someone’s P/MC/Assumption, analogy, counterexamples, generalization, principle, support, etc…)

Only 1 AC is 100% descriptively accurate

Eliminate wrong AC tactic for Agree/Disagree

Eliminate any that Speaker 1 does not take a stance on

AC Type for Agree Question

2 No’s

Choose the AC both speakers would say Yes to.

AC Type for Disagree Questions

1 Yes & 1 No

Choose the AC that 1 person would say Yes to & the other would say No to.

If stuck on Agree/Disagree Question

Use a T-chart