#9 - Gecko lizards are found in any environment where there

[Administrator]

Please post your questions below!

[LSAT2018]

How would this be diagrammed?
Is this a Mistaken Reversal/Mistaken Negation?

[fersian]

I would also appreciate a diagram on this.

[Adam Tyson]

It would probably help to diagram both of the conditional relationships in the premises independently, like so:

Gnats Geckos (first sentence)

Gnats Wet (second sentence)

If there are no geckos then we trigger the contrapositive of the first rule, and we can conclude that there is not an abundant population of gnats.

Geckos Gnats

But we cannot then go from there to anything about wetness, for to do so requires a mistaken negation of the second claim:

Gnats Wet

Therein lies the flaw in this stimulus, and answer B describes it perfectly, also using a contrapositive:

Wet Gnats

Whether you label this one as a mistaken negation or a mistaken reversal doesn't matter, because those two flaws are logically equivalent and are the contrapositive of each other. All you need to know is that the evidence about gnats (there aren't many) tells us nothing about the presence or absence of wetness, nor does wetness tell us anything about gnats.

[j199393]

Hello,

I diagrammed the first sentence incorrectly:

Gecko lizards are found in any environment where there is an abundant population of gnats.

Geckos --> Gnats
(It should be Gnats--> Geckos)

Can someone explain how to know that gnats are the sufficient condition and not the necessary so I don't make this mistake in the future?

Thanks

[Jeremy Press]

Hi j1993,

Good question, and it's all wrapped up in the one tiny little indicator word "any," which is an indicator of a sufficient condition. Since "any" modifies "environment where there is an abundant population of gnats," the "abundant population of gnats" should be diagrammed as the sufficient condition (on the left side of the arrow). When it comes to conditional diagramming, remember to follow the indicator words, not necessarily the order of presentation of concepts in the sentence.

I hope this helps!

[annabelle.swift]

Hi, I did not choose E, but I'm having trouble completely eliminating it. This was my thought process:

We know that geckos can survive w/ lots of gnats and wetness. We don't need to know at all whether or not geckos can survive in a dry climate since dry isn't the logical opposite of wet so dryness will never come into play in this set of if-then statements.

Is this good reasoning? I get why B is the right answer, but I just feel like I couldn't quickly eliminate this answer as a loser. Also, please don't say E is just irrelevant-- I'd like to know why it's irrelevant. Thank you so much!

[Adam Tyson]

Dry is the polar opposite of wet, annabelle.swift, but it still falls within the category of things that are not wet, so a dry climate would be relevant and would trigger the contrapositive of the second claim. Gnats could not survive there because they need a wet climate.

A good Flaw answer will point out something that causes a problem for the author. So let's imagine this conversation with the author:

Us: "Hey pal, you forgot something! Maybe sometimes geckos can live in dry places with not many gnats! Whattaya think about that, huh? Do you feel stupid?"

Author: "Actually, I didn't forget that. I told you very clearly that gnats can only live in wet climates, so in a dry climate there could not be any gnats. And so what if geckos could live somewhere dry? I am talking about a place where there are no geckos. Go away now, stop bothering me."

So you see, answer E poses no problem for the author, other than to be an annoyance (because, yes, it is irrelevant). That means it does not describe a flaw in the reasoning.