Q16 - Theorist: To be capable of planned locomotion

[layamaheshwari]

I was on the verge of selecting A, but went with C at the last minute (and am now kicking myself). Could someone please explain why C is wrong and A was, indeed, right?

[zhm222006]

Hi there. I eliminate C because it talks about "purpose" which I think is out of scope. Wish helps.

[ManhattanPrepLSAT1]

This one is all about linking together the relationships.

First, two requirements of planned locomotion are named: forming an internal representation of the organism's environment and controlling movement of muscles by sending messages. We further learn that have those traits means the organism must have a central nervous system.

We could infer from the above that for an organism to be capable of planned locomotion, it must have a central nervous system. But this argument doesn't reach that conclusion and instead negates the logic. Answer choice (A) refers to negating (or reversing) the logic of an argument.

Incorrect Answers
(B) reverses the logic of the first premise. While these terms are relevant to the argument, the reversed logic described here isn't assumed in the broader conclusion about central nervous systems and planned locomotion.
(C) is out of scope. The argument leaves open the possibility that other purposes of creating an internal representation of the organism's environment could exist.
(D) is out of scope. The argument assumes nothing about the reason why adaptations came about.
(E) reverses the logic in the second premise. It's stated that a nervous system is essential to an organism capable of creating an internal representation of the organism's environment while also being able to convey messages to muscles in order to control their movement. But this answer reverses half of this logic.

[krisk743]

Hey so I have a question about this. I knew immediately this is a conditional swap but isn't this a sufficient necessary swap and not a necessary sufficient?

I didn't chose A because of that, I chose B. I know that B was stupid to chose but thought it was stated the reversal but just in words and not simply as "a swap".

Isn't there a difference between the two kinds of swaps and isn't it significant? Or it doesn't matter. It's dumb questions like this that put me back for no reason.

If any admin can let me know soon i'd appreciate it

[jiangziou]

I eliminated A for the same reason. Please help!

[ohthatpatrick]

There's no inherent difference between an answer that says:
"An author confuses a necessary condition with a sufficient one"
vs.
"An author confuses a sufficient condition with a necessary one"

If we had the argument ...
"All NFL players are rich. Since Bob is rich, he must be an NFL player"
... then we have committed the Conditional Logic flaw (nec vs. suff), and either of the above answers would be fine as a correct answer.

If we had more than one conditional, such as
"All NFL players are rich. All people who favor low taxes are rich. Bob favors low taxes, so he must be an NFL player."

THEN, we might have to read more closely
"An author confuses a sufficient condition for being rich with a necessary one"
vs.
"An author confuses a necessary condition for favoring taxes with a sufficient one"

NOW, only one of them is correct. We need to think about which of the two conditional statements was abused in the author's thinking.

Since her final argument move is
"If Bob favors low taxes, he must be an NFL player",
then her thinking is that
"Favor low taxes --> rich" + "rich --> NFL player"
.........(correct)............................(incorrect)

If we know that the conditional she botched is the one from NFL -> rich, then we can't pick an answer saying she botched a conditional about "favoring taxes".

So the first answer option would be correct.

==================

For Q16, we have

Locomotion --req's---> rep internal env AND send msgs

Rep internal evn AND send msgs ---req's--> central nervous system.

Putting it together:
Locomotion ----> rep internal evn AND send msgs --> central nervous system

Because of this chain, we can say that "Locomotion requires a central nervous system".

The author's final statement is in an illegal negation:
~Locomotion --> ~central nervous system
and its contrapositive would look like this
Central nervous system --> Locomotion

(A) is describing the fact that what we CORRECTLY knew was that
Locomotion -------> central nervous system

The author's conclusion is saying
Central nervous system ----> Locomotion

"Central nervous system" was revealed to us as a NECESSARY CONDITION for possessing the capacity of locomotion.

Now, in the conclusion, it's being portrayed as a SUFFICIENT CONDITION for the capacity of locomotion.

Hope this helps.

[AyakiK696]

I got the right answer for this, but what I'm still a little confused by on this question is that it seems that you can take both A and B to get to the same answer?

The original statement is: L -> C
The author concludes that: -L -> -C

And so we know that he's negated the statement, by taking the contrapositive of the original statement and then switching up the sufficient condition and necessary condition. This aligns with A.

However, it also seems to align with B? If the theorist gets from L -> C, we can also say that he assumes that C -> L and thus gets -L -> -C right? I'm not quite so sure where I've gone wrong in the logic chain... I understand that he doesn't HAVE to assume this fact for his argument to work, but it seems like both answers get us to his final conclusion.

[ohthatpatrick]

The first premise is
Loco --> Int. Rep AND Msgs to Muscles

The second premise is
Int. Rep AND Msgs to Muscles --> Central Nerv Sys

If the author assumes a rule like (B), which says
Msgs to Muscles --> Loco

Could she get to her conclusion that says
Central Nerv Sys ----> Loco?

I don't see any way you could combine (B) with the available premises to derive the conclusion.

Given that the author's conclusion is saying,
"All organisms with central nervous system have locomotion"
the author thinks that
"IF central nervous system --->" goes somewhere.

But we don't have any rules that say "IF central nerv sys ---> _______ ", and choice (B) doesn't address that concern at all.

Hope that helps.

[LolaC289]

I got the right answer for this, but what I'm still a little confused by on this question is that it seems that you can take both A and B to get to the same answer?

The original statement is: L -> C
The author concludes that: -L -> -C

And so we know that he's negated the statement, by taking the contrapositive of the original statement and then switching up the sufficient condition and necessary condition. This aligns with A.

However, it also seems to align with B? If the theorist gets from L -> C, we can also say that he assumes that C -> L and thus gets -L -> -C right? I'm not quite so sure where I've gone wrong in the logic chain... I understand that he doesn't HAVE to assume this fact for his argument to work, but it seems like both answers get us to his final conclusion.

I made the same reading mistake just like yours in this practice test.

Actually, if you read answer choice B again, you will find that it is not stating the logic-reverse mistake that the argument made, which goes from Having central nerve system-->Capable of Loco. Rather it's about Sending messages from central nerve system--->capable of Loco, which is just an intermediate conditional logic statement in the argument. I guess because they all have the same "central nerve system" part, it tends to trap careless readers like us.

But I do understand your confusion and have the same question. Is the "negating the sufficient" (A-->B, thus～A-->～B)flaw equivalent to the "reverse logic" flaw(A-->B, thus B-->A)? I guess these two are inherently the same, that they all assume B-->A. But they seem different formally so I want to make sure.