#17 - Although Pluto has an atmosphere and is much larger

[James Finch]

Hi Cascott,

It looks like you're misreading what (E) says; it is purely a principle, and doesn't directly address any particular celestial body.

As to why it's correct, it's the only answer choice that gets us from being formed originally as a moon not a planet, which is what we need to justify the argument in the stimulus.

Hope this helps!

[cascott15]

@James Finch, sorry if I didn't explain well. What I mean is that the argument tells us that Pluto isn't a planet because it was formed around Neptune and later ejected. It doesn't mention the sun anywhere.

Knowing what I do about our solar system, yes, E makes sense. However, this question assumes you know that planets orbit the sun and that Pluto also orbit the sun. According to the stimulus alone, Pluto could be floating off into a different galaxy somewhere right now.

So I guess the takeaway is that we are allowed to make bring in outside information about proper nouns?

[KelseyWoods]

Hi Cascott!

Nope, you don't need to bring in any outside information to answer this question--and you shouldn't!

Let's go back and make sure we're clear on what we're trying to do in a Justify question. In a Justify question, you are trying to prove the conclusion 100% by adding new information that was not previously stated in the argument. So the first thing we need to do is identify and focus on the conclusion. The conclusion of this argument is "Pluto is not a true planet." So in the answer choices we are looking for additional information that will help us prove that Pluto is not a true planet.

Answer choice (E) says that forming in orbit around the sun exclusively is a REQUIREMENT for being a true planet. The conditional diagram for answer choice (E) would look like this:

True planet Formed in orbit around the sun exclusively

The contrapositive, then, would look like this:

Formed in orbit around the sun exclusively True planet

So if there is a celestial body that was not formed in orbit around the sun exclusively, then it is not a true planet. What do we know about Pluto based on this stimulus? It was formed in orbit around Neptune. Therefore, Pluto was not formed in orbit around the sun exclusively and so it cannot be a true planet. We've proved our conclusion 100%!

Also notice that we can prove that conclusion without any actual knowledge or understanding of astronomy. In a Justify question, we are told to assume that the answer choices are correct. If they changed answer choice (E) to say "For a celestial body to be a true planet it must have formed in orbit around the planet Mars exclusively," it would still be a correct answer. It may not be true in the real world. But if the LSAT tells us to assume that true planets have to form around Mars and Pluto formed around Neptune, then Pluto would still not be a true planet.

A key takeaway here is that it's always important to focus on conclusions and have a clear idea of what different question types are asking you to do and what you're looking for in the answer choices--it's so easy to get confused otherwise!

Hope this helps!

Best,
Kelsey

[cascott15]

Kelsey, thank you for your reply. I was confusing this with an assumption question, so I was looking for how the answer and stimulus connected. After reading your post, I also read Powerscore's handy article about the difference between justify and assumption questions and am feeling more confident now.

Thanks for your patience. I'll have to be more mindful of getting the two mixed up!

[lsatryan]

I still don't think the answers make sense, because of the word "sun"

[blade21cn]

You have to realize: orbit around the planet Neptune → not in orbit around the sun exclusively. Thus, mentioning of "sun" is totally relevant, as such information can fully interact with other elements in the argument.

[Adam Tyson]

Exactly right, blade21cn! The sun is relevant because Pluto did NOT form in orbit around the sun exclusively.

For everyone concerned about "sun" being some new idea in the answer, Justify the Conclusion answer can, and usually do, bring up something new! Just like a Strengthen question, in order to help make an argument better, or perfect in this case, you have to have some new information. After all, you can't make an argument better just be repeating what the author already said!

This argument is that Pluto cannot be a planet because it formed around Neptune. So we need an answer that says forming around Neptune is sufficient to prove it is not a planet. An answer that says "to be a planet you have to do some other thing that Pluto didn't do" is exactly what we are looking for! "You have to form around the sun exclusively (so not around anything else)" does precisely what we need it to do by telling us that planets must have a characteristic that Pluto does not have.

I hope that sheds a little sunlight on the problem!