They're wrong. (B) is not a valid argument. In other words, truth of the premise does not guarantee truth of the conclusion. If they interpret the argument as conditional, then I can see why they'd think it's valid. But the problem is that the premise is NOT expressing sufficiency / necessity. It's merely capturing a relationship between a fixed set of past events which (and here's the crucial difference) by no means guarantees that the relationship will hold in the future. Premise tells us that each time in the past where we had "winter high snowfall + spring thaw" we saw "river overflow." This is at best a causal statement. In order for the conclusion (which is a prediction about future events) to follow, we'd have to make a bunch of assumptions. For example, no major climate differences b/t this year and previous years. That's a huge assumption. Think in terms of weakening if that helps. What if you learn that this year we're experiencing an unusually slow onset of spring / warm weather which leads to a slow melting of snow. A slow snow melt may well not lead to river overflow. That would severely weaken the argument. And you can only do that because the argument was never valid to begin with.

I hope this makes sense. If not, I'm happy to say more. I would encourage you to watch the video again though. J.Y. mentions this point about the difference b/t causal v. conditional claims at the very beginning when he maps the stimulus out and chooses not to use the conditional arrow.

I don't think that's the issue. I think the issue you have is with the question stem. The question stems says which one of the following "if valid" most justifies. It sounds like you're objecting to (D) because it conflicts with what you learned in statistics.

Yeah, I think if you're targeting around a 160, then it might be okay to systematically skip these.

It does feel like a shame though since when they click, they click and you're counting the points! :smiley:

I just checked analytics and in the most recent 12 PTs, there were on average 4 PSA and 3 SA questions per PT. That's a lot of points to give up!

Hmm, do you mean "halfway in terms of explaining B"?

The reduction in cars comes from the stimulus. It's the existing (and only) premise. I think the point is that while this premise already supports the conclusion, B adds a new dimension of support, so to speak. Whereas in the stimulus, the support is that you walking has the effect of your car not polluting, B tells us that you walking has the additional effect of other people's cars polluting less. How? I think this is where your comment comes in about NRV and MV and precisely how that happens.

This is a strange question and definitely feels like an older LSAT! I'll say upfront that I cannot satisfactorily address your question. I think it's just weird that the LSAT thinks we should know what counts as "hazardous waste." But anyway, here are my two cents.

I think the key inference is this: when the stimulus says that the mussels improve water quality by removing hazardous wastes, we can infer that either the wastes (1) stay in the mussels (trap), or (2) the mussels transform them to something harmless (neutralize). But the mussels cannot simply discharge the waste unchanged back into the water. If they did, they would not have improved water quality.

In (E), option (2) is explicitly ruled it out so we're left with just option (1), the hazardous wastes stay inside the mussels.

Now, your question:

@jmarmaduke96714 said:

Why would it not be possible for the mussels to absorb some of the hazardous waste, but not necessarily become hazardous waste themselves?

I think this is a part-to-whole inference issue. Sometimes part-to-whole inferences are fine, sometimes not.

You can think of an all-star NBA team where each player is great, among the best, but the team is not so great because the players don't normally play together and so just suck at playing as a team. Other examples include emergent phenomenon, like how each individual ant is rather dim, but a colony of ants exhibit intelligence.

But then you have situations where part-to-whole inferences are okay to make. For example, if the each and every piece of a shack is made out of wood, even the nails, then it's fine to say that this is a wooden shack. In fact, I think even if the nails were metal, it's still fine to say that this is a wooden shack.

So we take the claim that since the mussels (whole) absorbed hazardous waste (part), and they're not neutralizing it, does it mean that the mussels must be regarded as hazardous waste? I don't know. It's not a must be true claim, but then we're not doing an MBT question. It's an MSS question, so I think it is okay to say that sure, we'll make the loose inference. It's like in RC, you have to make these kinds of loose, MSS-style inferences.

Yeah, good question. That's the heart of the logic here. Take a statement like "whether you like strawberry ice cream will determine whether you like tonight's dessert."

How many ways do you suppose this statement could turn out? If you like strawberry ice cream, then you will like tonight's dessert. If you do not like strawberry ice cream, then you will not like tonight's dessert.

I think using "whether" in this way is just a way in English to compact something that otherwise would have to be written out with more statements. Does that help?

Good point. Looking at the model's distribution, you'd have to be around a 178 to have a 50% chance of getting this question right. No thanks!

Good question! But it's not (A) that makes the assumption. It's Gerald who makes the assumption. Notice that for Gerald's analogy to make sense, you have to figure out that Gerald assuming trespassing is illegal. (Imagine if the question stem asked you to do a necessary assumption on Gerald's argument.) In order for Kendra's response to Gerald, which is also an analogy, to make sense you also have to realize that she's assuming that loitering/harassment is illegal.

Oh I think you've got it exactly reversed.

Analogy: "governments fund NEO research for the same reason that people insure their homes." That's an analogy. It's only at the analogy level that "same reason" means the same thing. At the literal level it's not the same reason. One reason is to make sure that humanity isn't wiped out. The other reason is to make sure a family's most valuable asset is protected. But they're the "same reason" in that analogously speaking, just like how protecting your family's most valuable asset makes good fiscal sense to you, protecting humanity makes good fiscal sense to the government.

Claim: "buying home insurance makes good fiscal sense." Note that this is not an analogy. It's just a claim about buying home insurance being a good idea.

Right, I think you can say that the researcher observed that in those instances the society moved from a currency system to a barter system. But the researcher doesn't say that. Instead he says that they "revert to the original barter system." That's problematic. You're trying to argue to the conclusion that the barter system is the original system, something you can revert to. You can't just declare that it is in a premise. I mean you could but then your argument would be circular.

I think that's what J.Y. was trying to point out at 2:10.

Hey there! Did you see the response / conversation below LSATcantwin? I presume you're asking about (E) right? I think that might help.

@2396 that's PowerScore's terminology the "mistaken reversal" and "mistaken negation" right? Just want to be clear because I don't think 7Sage uses those names.

Given a conditional statement S: if A then B, the logically equivalent statement is if not B then not A. That's the contrapositive of (S).

The converse of (S) is if B then A. "mistaken reversal"

The inverse of (S) is if not A then not B. "mistaken negation"

But note that the converse of (S) and the inverse of (S) are contrapositives of each other, meaning they're logically equivalent statements. They each imply the other in other words. I think that therefore if an argument assumed a converse, it also assumed an inverse, and vice versa?

I guess I can see why PowerScore wants to call it a "mistake" but there's nothing inherently "mistaken" about those statements. They're fine, leave them alone. Just don't confuse if A then B with if B then A.

@2396 said:

I thought the flaw was stating that since neutering usually leads to improper bone development and that definitely ("in turn leads to" implies a causal result every time) leads to arthritis problems later on, then concluding that, "not neutering will solve this problem," is flawed logic, since there could be other reasons for why a dog has arthritis problems (i.e. there could be more than one sufficient condition).

Causation ("reasons") and implication ("being a sufficient condition of") are very different things, though they do share similarities. An implication is far stronger than a cause in a sense and completely orthogonal to it in some other sense. In our world, smoking does cause (is a reason for) cancer but smoking is not sufficient for (doesn't imply) cancer. One plus one implies two but one plus one does not cause two.

The stimulus contains only causal premises. It's true that there may be multiple causes for arthritis. But that's accommodated by the soft language of "protect." The conclusion is where a conditional is present but we can understand that by merely postulating a world where a dog owner wants to protect their dog from arthritis and evaluate whether in that world the causal premises support the consequent, i.e., the "necessary condition."

I thought it could be made clear by changing the conclusion to "Thus, if you want to protect your dog from arthritis you should not neuter your dog in early puppyhood."

Then it feels like the argument is no longer vulnerable to criticism. Yes, what (E) says about other ways to get arthritis is still true, but it doesn't much affect our argument.

http://classic.7sage.com/get-the-lsat-trainer/

@wraith985-4026

said:

It’s like magic – the theory just appears when it’s needed, and is tucked safely out of mind when it’s not, ready to be invoked again on a moment’s notice.

That's a good way to put it.

Initially I'd skip these - time sink - but later on in my studies I started "see the shapes" in my head. I actually think that a good number of the Parallel Flaw questions especially the ones that use Lawgic are fairly straight forward meaning they're often Common Invalid Argument forms.

One thing that helped a lot was BR and painstakingly translating into Lawgic or mapping out every single answer choice.

[Edit]

Lesson citation:

http://classic.7sage.com/lesson/7-common-invalid-argument-forms/

Way to go @2543.hopkins!

@williamjkwon642.j.kwon You can see J.Y. do the games from PT 71 live:

http://classic.7sage.com/lsat_explanations/lsat-71-section-2-game-1/

Don't look at it though if you haven't already done PT 71 cause you'll ruin the game. But it's true that the way he does the games is not exactly the same as the way he teaches the games.

@licknee10505 PT downloads work fine for me. If it doesn't work for you, let @7sagestudentservices know.

@9084 If your objective is to obtain as many PDFs of the PTs, then now's the time to get the Ultimate course.

@igbodoe249 Ohhhh yeah, if you add up all the paper I used it'd probably amount to a big tree having sacrificed itself for my LSAT studying and whatever thing printer toner comes from.

But seriously, girl, or dude, you can't go cheap on the printing. Use the extra paper! It makes a difference.

@igbodoe249 Oh I see. Well, that's all I got. :)

No, unless you manipulate the PDFs.

It's better to practice them on two pages b/c that's what you'll get on test day.

I'm not sure if this is a loophole but I can get to RC explanations via the Logic Games page. For example:

http://classic.7sage.com/lsat_explanations/lsat-1-section-2-game-1/

[Edit: I'm logged into my Ultimate course.]

Try to wake up early and study first thing in the morning like @2543.hopkins

J.Y. wrote about it here:

http://classic.7sage.com/lesson/the-three-worst-lsat-mistakes/

The point I would like to add is that waking up early in the morning actually means going to sleep early at night. It doesn't mean go to bed at 1am and force yourself to wake up at 5am... that doesn't work and I'm speaking from personal experience.

As far back as 2011 research has shown that Netflix dramatically reduces piracy. Why? It's simple. If people have convenient and affordable access to legal content, they don't pirate. Conversely, if people don't have convenient and affordable access to legal content, they do pirate. If we want something, we'll find a way to get it.

Our analogue of Netflix is 7Sage (or LSAT Blog), offering convenient and affordable access to legal content. If LSAC takes this away from us, what do they think we're going do? "You know what it really was way too damn convenient to print out my PTs. I want inconvenience in my life."

No. Actually, even though I'm done with the LSAT, I might just pirate some PTs out of spite / to increase the number of seeds. Just kidding @7sagestudentservices, that would be un-sagely of me to do.

You'd think a company that places such a high value on logic (I'm talking about the LSAC) would understand the incredibly simple logic behind this argument (also know as reality). But likely the people who write the questions are not the people who run the company.

I agree with @nielsinha488 about having a more forgiving schedule. June will be tough for someone who's full time devoted to LSAT studying and wow you have a lot on your plate already! For example, it took me a full school year plus the summer plus part of the new school year.

Definitely enroll here (7Sage) if you haven't yet. If you need something else beyond that (your probably won't), then consider the Trainer.

No Powerscore.