PT154 S1 Q9 ExplanationGecko lizards are found

Answer choices, explained

1. A

   Not Assumed Too Strong: only24% picked this

   presumes, without providing justification, that gecko lizards can survive only in environments with

   This answer is itself making a Necessary vs. Sufficient error. We were told that abundant gnats are sufficient to indicate geckos. lots of gnats ? geckos This answer is saying that the author was assuming that abundant gnats are necessary for geckos. geckos ? lots of gnats This answer would work if the author had messed up the conditional in the first sentence, because it's saying, "The author incorrectly saw the conditional in the first sentence in reverse". The author didn't misuse the conditional in the first sentence; he botched the one in the second sentence.

   24%
2. B

   Correct68% picked this

   presumes, without providing justification, that all wet environments contain abundant populations

   Why this is right

   Did the author assume that Wet climate ? abundant gnats ~abundant gnats ? ~Wet climate ? Yes! After all, the author's final move was thinking, "There is no abundant population of gnats here. Consequently, the climate must not be wet". That's making this move: ~abundant gnats ? ~Wet climate When we're reading a Necessary Assumption answer choice, on Necessary Assumption or on Flaw (takes for granted / presumes / fails to establish), and that answer is conditional, we generally want to just diagram how that conditional looks, and then ask ourselves whether the author made that move. Did the author go from establishing the idea on the left to thinking/concluding the idea on the right? Crucially, we need to consider the contrapositive of the answer we're looking at, because correct answers are usually written in a contraposed form of how we would recognize the argument. For example, here the answer gives us Wet climate ? abundant gnats but the contrapositive form matches the argument. ~abundant gnats ? ~Wet climate

   Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.

   68%
3. C

   Not an Objection4% picked this

   does not consider whether small populations of gnats can survive in climates that

   Since this begins with fails to consider / overlooks the possibility, we can ask ourselves whether the following idea would be a weakening Objection. Can we hurt the author's argument by saying, "small populations of gnats can survive in non wet climates"? No that would be easily tolerated by the author. He thinks there is no abundant population of gnats, but he can still allow for there being a small population of gnats. And he thinks this climate is not wet, which is what the answer is also saying. So this "objection" is perfectly compatible with what the author was saying. A correct answer would be does not consider whether small populations or no populations of gnats are sometimes found in climates that are wet. This is just an awkward way of saying, "just because there's not an abundant population of gnats doesn't mean the climate isn't wet. You could have a wet climate, that doesn't have an abundant population of gnats."

   4%
4. D

   Irrelevant2% picked this

   does not mention whether gecko lizards eat anything

   It's true, the author didn't mention whether geckos eat things other than gnats. In fact, the author never mentioned that geckos eat gnats. Why are we talking about what geckos eat? That has nothing to do with the logical flaw of this argument, which involves assuming that "since gnats require a wet climate, any place without gnats must not be a wet climate".

   2%
5. E

   Not Assumed2% picked this

   fails to establish that some gecko lizards could not survive in a dry climate containing only a

   When an answer begins presumes / takes for granted / fails to establish, we treat it like Necessary Assumption. Was this author needing to assume that "some geckos couldn't survive in a dry climate containing only a small population of gnats". It doesn't seem like the author was every specifically addressing any scenario like that. Let's negate it and see if it would weaken: "no gecko lizards could not survive in a dry climate with few gnats". Let's remove the double negative: "all geckos could survive in a dry climate with few gnats" Would it hurt the argument to say, "All geckos could survive in a dry climate with few gnats"? Nope. We can really only hurt the argument by saying something like, "Isn't it possible that there are wet climates that lack abundant populations of gnats"?

   2%