LR Question 23 Explanation
QUESTION TEXT: A species in which mutations frequently occur will…
QUESTION TYPE: Flawed Parallel Reasoning
CONCLUSION: Frequent mutations ➞ survive
REASONING:
- Frequent mutations ➞ adaptations
- 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.
___________
- 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. -
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.
- CORRECT. This matches exactly:
Perfectly honest ➞ tell truth
Morally upright ➞ tell truth
Conclusion: Perfectly honest ➞ morally upright - Reasoning: Productive ➞ well drained ➞ good soil
Conclusion: productive ➞ good soil
This is a good argument! - 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!
More Resources for Flawed Parallel Reasoning Questions
- Conditional Reasoning Article: Learn about conditional statements.
- LR Diagrams Guide: Learn how to draw LR diagrams.
- Flaw drills: Practice identifying flaws.
- Intro Course lesson: This intro course lesson covers Flawed Parallel Reasoning questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers flawed parallel reasoning questions.
Confused on how this is even a flawed argument. Doesn’t the “only if” statement flip that sentence so it’s more like Adaptations = survive? So therefore A to B, B to C, therefore A to C.
I see why C is the right answer but don’t see why either are flawed in the first place.
Nope, “only if” introduces a necessary condition, not a sufficient one.
The sentence can be translated to: A species cannot survive unless it develops those adaptations.
So if survival happens, the adaptations must also happen.
That diagrams as: Survive -> Adaptations.
The sentence does not say adaptations GUARANTEE survival (it does not say Adaptations -> Survive). A species might develop new adaptations and still fail to survive because the environmental change is too extreme, the adaptation is insufficient, there are other threats, etc.
An easy analogy is: You can enter the bar only if you are over 21.
That means we know: If Enter bar -> Over 21.
But we don’t know: Over 21 -> Enter bar. You could be denied for a multitude of other reasons.
Which means we get:
Reasoning:
1. Frequent mutations -> Adaptations
2. Survive -> Adaptations
Conclusion: Frequent mutations -> Survive
But we know nothing about the relationship between those two.
Hope that helps! Let me know if you have further questions.