By referring to the Universal Declaration of Human Rights as "purely programmatic" (line 49) in nature, the author mo...

Masada on January 26, 2020

question # 14

can someone please explain to me why answer choice b is somehow incorrect? the last sentence in the passage states just that "moons in solar system s4 all orbit the planet alpha" I got b

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AndreaK on January 28, 2020

Hi @Masada,

I am seeing video lessons for logical reasoning appear on my end when I attempt to view the question you posted about.
Is this what you're referring to? If so, if you are able to specify which video (and where within) or example from the lesson you're having trouble with, I'm happy to help you out!

Skylar on January 28, 2020

@Masada, happy to help!

As you note, the passage concludes that "the moons in solar system S4 all orbit the planet Alpha." Our task is to find the answer choice that guarantees that this conclusion is true based off the premise that every moon orbits some planet in its solar system. Currently, this is a flawed argument because there is no support connecting the premise to the conclusion. Namely, how do we know that the moons in S4 all orbit Alpha? What's to say that they don't all orbit the planet Beta? Or what's to say that some of them orbit Beta and others orbit Alpha? We need to find an answer choice that will explain why Alpha is the specific planet that all of these moons orbit.

(B) is incorrect because it fails to specify why Alpha is the specific planet all the moons orbit. (B) states that "every moon in S4 orbits the same planet," but the identify of this "same planet" is left unspecified. Let's say that every moon in S4 orbits is Beta - this would make (B) true, but it would not make the conclusion of the passage (that all the moons in S4 order Alpha) true. This means that (B) does not guarantee the conclusion.

Does that make sense? Please let us know if you have any additional questions!

AndreaK on January 28, 2020

Hi @Masada,

Oh, my bad. I see now you specified it was question 14!

So, this is a sufficient assumption question. That means, it's our goal to guarantee the truth of the conclusion. Our correct answer choice is going to give us the piece of information we need to do that.

Our conclusion is that the moons in solar system S4 *ALL* orbit planet alpha. Our evidence for that is: Any moon, by definition, orbits some planet in a solar system.

So, with just that piece of evidence (that any moon orbits some planet in a solar system), how are we then supposed to guarantee that ALL the moons in S4 orbit SPECIFICALLY the planet ALPHA?

Think about the information we don’t have about the solar system in question. For one, we don’t know if alpha is the only planet. If it were, then by definition, all the moons would have to orbit alpha. However, what if it isn't the only planet? If it’s not the only planet in S4, then maybe some or all of those moons are orbiting around another planet.

If our goal is guarantee that the author’s conclusion (the moons in solar system S4 *ALL* orbit planet ALPHA) is true, specifying that alpha is the ONLY planet in S4 would do the trick. Because then, we know those moons have no where else to orbit so they must all be orbiting alpha.

That gets us to answer choice C.

In answer choice B, “Every moon in S4 orbits the same planet” the problem is we don’t actually know what planet that is. They language says they all orbit “the same planet.” Well, what if that planet isn’t alpha? We would need to know that planet was alpha for this to work, which is why C is correct.

I see how this question could be tricky. My guess is you understood the concept, but didn’t realize you were relying on an unstated assumption in your reasoning. The assumption is what you need to isolate in your thinking, as opposed to using it (when it may be unwarranted to do so) to make other deductions with. The LSAT is all about bringing those unstated, sometimes obvious seeming assumptions to light. If you can spot the assumption you’ve targeted the place the right answer lies. Different questions stems have you manipulate assumptions in different ways.

Hope this helps!