LSAT 137 | Section 3 | Logical Reasoning: Q23

LR Question 23 Explanation

QUESTION TEXT: A species in which mutations frequently occur will…

QUESTION TYPE: Flawed Parallel Reasoning

CONCLUSION: Frequent mutations ➞ survive

REASONING:

1. Frequent mutations ➞ adaptations
2. Survive ➞ adaptations

ANALYSIS: This argument takes two conditional statements that share a necessary condition. Then it incorrectly assumes that one of the sufficient conditions leads to the other. Look for this structure:

A ➞ C

B ➞ C

Therefore, A ➞ B.

___________

1. Reasoning: Sturdy ➞ properly built ➞ every stone supports another stone
   Conclusion: sturdy walls must have every stone supporting another stone
    
   This is a good argument, assuming the conclusion only refers to stone walls.

2. This is a different flaw; it flips between polar opposites:

   • Performed before a completely different audience every time. (i.e. total difference)
   • Performed before the same audience every time (i.e. total similarity)

   There can be a middle ground: audiences that are somewhat different, but not entirely different. You might get the same reaction from two audiences if they were 98% similar.

3. CORRECT. This matches exactly:
    
   Perfectly honest ➞ tell truth
   Morally upright ➞ tell truth
    
   Conclusion: Perfectly honest ➞ morally upright
4. Reasoning: Productive ➞ well drained ➞ good soil
   Conclusion: productive ➞ good soil
    
   This is a good argument!
5. Reasoning: Healthful diet ➞ well balanced ➞ fruits and vegetables
   Conclusion: Healthy ➞ fruits and vegetables
    
   This is a bad argument, but it makes a different flaw. Here, the author switches between “healthful diet” and “healthy”. Those are not the same thing. Maybe it’s possible to be healthy despite not eating a healthful diet!