LSAT 118 | Section 1 | Logical Reasoning: Q2

LR Question 2 Explanation

QUESTION TEXT: Commentator: Many people argue that the release …

QUESTION TYPE: Weaken

CONCLUSION: There’s no reason to think CFCs harm humans by damaging the ozone layer and increasing UV radiation.

REASONING:

• A supernova 300,000 years ago damaged the ozone layer.
• That damage was greater than the damage caused by CFCs today.
• Our ancestors suffered no significant effects.

ANALYSIS: The argument relies on an analogy:

• Big ozone damage in the past didn’t hurt humans.
• Therefore smaller ozone damage today won’t hurt humans.

The commentator is assuming that humans today would respond to increased UV radiation in roughly the same way as our ancestors did 300,000 years ago.

But suppose our ancestors were much more resistant to UV radiation than modern humans. Then, the analogy becomes much weaker.

The best weakening answer will identify a relevant difference between ancient humans and modern humans. That’s how you break down an argument that relies on an analogy.

___________

1. This compares extraterrestrial and terrestrial causes of ozone damage. The argument isn’t about what causes ozone damage. It’s about whether ozone damage harms humans.
2. The fact that ozone damage still occurs naturally today doesn’t tell us whether CFC-caused ozone damage is harmful.
3. CORRECT. The commentator’s evidence comes entirely from what happened to those ancestors. If our earliest ancestors were more resistant than we are to UV radiation, then the comparison is much weaker.
4. Interesting, but irrelevant. The argument is about whether ozone damage harms humans, not how long the damage lasts.
5. This is tempting. It says genetic changes occurred during the period of the supernova. But it doesn’t tell us whether those changes were harmful, beneficial, or unrelated. The argument says there was no significant effect on our ancestors. Genetic changes alone don’t undermine that claim.