LSAT 138 | Section 3 | Logical Reasoning: Q9

LR Question 9 Explanation

QUESTION TEXT: All laundry detergents contain surfactants, which can…

QUESTION TYPE: Weaken

CONCLUSION: We have no evidence that ‘ecological’ detergents are greener than regular detergents.

REASONING: All laundry detergents have surfectants (including ‘ecological’ detergents), which are harmful.

We don’t know what effect the other ingredients in detergents have on the environment.

ANALYSIS: This is a bad argument. We don’t know what the ingredients in ecological detergents do.

We can only conclude that we know nothing. But the argument goes too far and concludes that the ecological detergents are as harmful, even though we have no evidence.

The right answer weakens the argument by a different method. It shows that while ‘ecological’ detergents have surfectants, they have less.

Many of the wrong answers don’t distinguish between ecological and non-ecological detergents. To weaken the argument, you must show an advantage for ecological detergents or a disadvantage for non-ecological detergents.

___________

1. CORRECT. This shows that ecological detergents cause less known harm than regular detergents. They have smaller quantities of a known pollutant.
2. This is a point in favor of regular detergents. It doesn’t help us weaken the argument.
3. This tells us that detergents vary in their environmental harm, but it doesn’t help us show that ecological detergents are less safe. We need more specific information.
4. That’s bad news….but this answer choice doesn’t distinguish between ecological and non-ecological detergents. Maybe they’re all bad.
5. This raises the harm done by ecological detergent. If it had said smaller amounts of ecological detergent, then this would be  correct.