LSAT 92 - Section 1 - Question 01

This is a Weaken question.

The stimulus is an advertisement that states Omnicide kills more species of insects than any other insecticide. From that premise, the advertisement concludes that Omnicide is the best insecticide for home gardeners, especially the ones who can't tell which insects are harming their plants.

But just because an insecticide kills the widest variety of insects doesn't mean that that's the best insecticide. A gardener who wants to protect her plants only wants to kill the harmful insects. This means the assumption in the advertisement's argument is that Omnicide kills only the harmful insects. Now, if that assumption is true, then the argument is pretty great. Omnicide is killing the widest variety of harmful insects. A gardener who doesn't know which insect is harming her plant should get Omnicide because it casts a wide net and increases the chances of killing the mystery pest.

But if that assumption were false, then this argument is severely weakened. Correct Answer Choice (B) cuts against that assumption. It says many insect species are beneficial to garden plants and Omnicide kills most of them. This weakens the argument to the point of directly damaging the conclusion. (B) is so powerful that it actually supports the opposite of the conclusion. This isn’t something that a correct answer in a Weaken question needs to do, but it is something that frequently occurs. Just be mindful that while some answers overshoot the standard, it doesn’t mean that they’re setting the standard.

Answer Choice (A) says some of Omnicide's competitors kill almost as many species of insects as Omnicide does. This doesn't weaken the argument. If anything, this only explicitly confirms that the competitors do not kill as many insects as Omnicide does.

Answer Choice (C) says merely protecting plants from attack by insect pests does not guarantee that the plants will be healthy. This is irrelevant. It could have been relevant if the conclusion were about the general health of plants. If that were the case, then of course damage from insects is only a partial consideration. We would also want to control for things like sunlight, nutrition, soil conditions, etc. But the conclusion is just about protecting plants from harmful insects.

Answer Choice (D) says Omnicide is more profitable for the manufacturer than most of their other insecticides. This is a classic bait trying to attack an argument by attacking the source. It doesn't work. The strength of the reasoning doesn’t turn on the profits. It might explain why the company is advertising Omnicide as opposed to another of their products, but that’s not our job here.

Answer Choice (E) says Omnicide does not kill weeds or mammalian pests like gophers or groundhogs. Similar to (C), this is not relevant because the conclusion is just about protecting plants from harmful insects. Again, this could have been relevant if the conclusion were about protecting plants from harm in general. If that had been the case, then other weeds or mammalian pests would be relevant considerations.