Five Tips for Necessary Assumption Questions [LSAT Logical Reasoning]

[@christinadeserio]

This is my weakest area in logical reasoning and this video really helped!

[@nnxj6125]

Most helpful video on this particular aspect of the LSAT that I've come across so far.

[@starwarsnerd16]

This is a helpful video and clears things up a little bit for me. I have struggled hella with necessary assumptions and have been heavily discouraged as of late. Your knowledge and breakdown has given me a bit of renewed hope LOL.

[@steve7741]

After reviewing a few of this LSAT instructor's videos, I am quite impressed. He is exceptionally knowlegable.. Of course, the LSAT is complex; not anyone, and no instructor, can change this challenging reality. So, improvement of LSAT performance does not entail any quick, simplistic "trick." That said, the LSAT score, with time and focus, can be improved, and even significantly. Finding a great instructor to compliment one's study endeavor can be valuable. So far, from what videos of his viewed so far, this guy seems to be a truly exceptional instructor. Best of everything to all in your study.

[@krkMuse]

I smile because people rarely understand defending assumptions. I mastered this and love to go over the LSAT when I am bored. Once you get this concept, you get every question right and try to change the questions from assumptions to strengthening to weakening to even "how could be this harder? "

[@jeniferwhite2172]

Do you have any video with that explanation.? I started this week learning NA. I did have a feeling it is similar to the strengthen and weaken concepts.

[@naomiokenn447]

Saying hi. Coming to ya from Blueprint !😌 Needed extra help understanding this, so far ....thank you!!!

[@rodneymanyepa]

Not studying for an LSAT but I’m building a very powerful app that uses conditional logic to collect user data. I realized that in structuring my conditional logic for determining input field variables, I needed to understand how to program required conditions to make a required input field sufficiently filled to meet the conditions for the determination of the next required input field. Stumbled on this channel and then realized a lot of programmers could use this, and not just LSAT students. Therefore, this logical thinking class can reach a wider audience if it includes programmers in its audience targeting.

[@jordanrattanavong2655]

Your videos are great. probably the best on YT. wish you had some RC content.

[@LuminateLSAT]

I've been thinking about ways to do useful RC content - I'm not allowed to show real passages from the LSAT, and it's difficult to write LSAT-like passages of my own, so that's why I've focused more on LR and LG issues. But perhaps another short tip-oriented video like this one, but for specific RC issues, would help? Stay tuned.

[@takara1485]

MY LIGHTBULB JUST FINALLY CAME ON AFTER SUCKING AT THESE! 😄 I pictured the top of an umbrella being a main assumption then the stem but (using multiple stems) as specific explanations that can also work.

[@amelaissa2789]

I love the umbrella example!

[@ElijahRoberts-h8y]

Excellent Video man. very helpful.

[@christopherbyron3833]

Wow this is such an amazing explanation

[@marksummers4101]

Holy shit, thank you! These have been whooping my ass, but I'm ready to dive back into them now. I really need to hear the bit about new information not present in the stimulus. Thanks, Kevin!

[@mdl8210]

Great video!

[@aharontamar]

The last part *connecting necessary assumptions to flaws* at the end really confused me! When is this applicable? How do they overlap and under what conditions? I used to find necessary assumptions by using the same method as finding flaws, and kept getting them mixed until I made an effort to differentiate. But it''s still not clear to me when and why they would hypothetically overlap. Thanks!

[@Bentami]

These are really great tips

[@tokhirivx3846]

This is great. Thank you!

[@SaraShTari]

Hi Kevin! Thanks for this great video. Just a question here... can we conclude that all sufficient assumptions are somehow necessary assumptions as well, but in contrast necessary assumptions are not necessarily a sufficient assumption for an argument?

[@LuminateLSAT]

No! Not all sufficient assumptions are necessary assumptions. Consider this argument: Since I studied a lot for the LSAT and am getting lots of sleep, I will get a high LSAT score. This would be an example of a sufficient, but NOT necessary assumption: Anyone who studies a lot for the LSAT will get a high LSAT score. This is sufficient to guarantee the conclusion because we know that I did study a lot for the LSAT. But it's not necessary because my initial argument was limited to people who BOTH studied a lot for the LSAT and were getting lots of sleep. I didn't have to believe that everyone who studied a lot -- including those who *weren't* getting lots of sleep -- would get a high LSAT score. I only had to assume that those who had both qualities would get a high LSAT score.

[@brooklynpiplup]

Great video.

[@FrancoPhysique]

Thank you!

[@adenwhw]

Hi Kevin. At the 4th tip, Is "There is no other explanation for how the items got on the floor" both NA and SA ?

[@LuminateLSAT]

Yes, that's right. If it were true that there's no other explanation, then that means it has to be the particular explanation described in the conclusion. So that's why it's SA, too.

[@postale1]

Weren’t you at Blueprint?

[@CallaXoLilly]

Hi, I know that a few other people have commented on this but I've read those threads and am still confused. Wouldn't "All winged pigs can fly" actually be the narrowest possible assumption that the argument can make (rather than the broader/stronger "anything with wings can fly")? I don't understand why we need to drag other animals into this if we can get from the premise to the conclusion with my narrower assumption.

[@LuminateLSAT]

It's important to distinguish what is being offered as a reason for the conclusion, and what is simply a description of the thing we're talking about -- which the author isn't presenting as a reason supporting the conclusion. Consider this: Mary likes studying. Thus, she's a good student. Would you agree that "If someone like's studying, then they are a good student" is necessary? If so, why wouldn't this narrower version be the extent of what's necessary: "If someone named Mary likes studying, then that person is a good student." The author doesn't have to assume people named John who like studying are good students, or people named Paul who like studying are good students, right? After all, the argument was just about a person named Mary. If something about that previous paragraph strikes you as odd, it's supposed to! Although it's true that the argument was about Mary, the fact that she was named Mary had nothing to do with the author's reasoning. What mattered was that this person -- whatever her name was -- likes studying. So the author's assumption really is broad -- Anyone who likes studying is a good student. If that were not true, the author's premise cannot be sufficient to prove the conclusion. Now consider this other argument: I have a roommate. Because she likes studying, and her name is Mary, she must be a good student. In that argument, her name being Mary is now part of the reason I believe she's a good student. In this version, the assumption is no longer about anyone who likes studying. It's about anyone who likes studying and is named Mary. Does this make sense? This is why I view "Anything with wings can fly" as a necessary assumption in the example argument. The fact that we're talking about pigs is not offered as a reason for the conclusion -- it's just the subject my argument happens to be about. The reason I think the thing we're talking about can fly is that it has wings; the fact it's a pig doesn't play a supporting role. That's why the broadest form of the necessary assumption is "Anything with wings can fly." (Keep in mind this statement implies various other ideas that are necessary -- All pigs with wings can fly, some pigs with wings can fly, the fact something is a pig does not prevent it from flying, etc.)

[@rayalin7558]

Hi Kevin, thank you for the video. I have one question regarding the last NAs about Timmy. I feel like if this argument about Timmy were in a NA question on my actual test, I probably would miss the answer choice similar to any of those you showed in the video. I am thinking only working hard on the assignments that are graded seems a sufficient condition for not being truly interested in the subject, so if the sufficient condition is negated, in order words Timmy did not only work hard on assignments that were graded, there is probably another way we could conclude that Timmy is not truly interested, right? (for instance, he never studies physics if its not school related) Probably I shouldn't confuse myself like that😅, but I would be forever grateful if you could give me some tips to cope with or avoid this confusion.

[@LuminateLSAT]

Very common concern, and one I'll make a video about. The key is recognizing that the author of the argument is the one who is saying that their premise automatically leads to their conclusion. If you can point out something that shows their premise cannot, by itself, guarantee the conclusion, that weakens the argument. So if we show that Timmy works hard on non-graded assignments, you're correct in saying that the author might be able to show that Timmy is still not truly interested in the subject for some other reason. But we've still weakened their argument, because we've shown that the author can't get to their conclusion using the premise they gave us. If Timmy works hard on non-graded stuff, the principle that "If you work hard only on graded things -> Not truly interested" means absolutely nothing to us. That principle would have nothing to do with Timmy, and have nothing to do with showing that he's not truly interested. Take this argument: If it's Monday, then I have go to work. Thus, I have to go to work. This argument is assuming that it's Monday. How do we know that? Because if it were not Monday, then the premise is irrelevant - there would be no reason to think this premise proves that I have to go to work. Now someone with your initial concern might say "But can't you have to go to work on Tuesday? Wednesday?" Yes, that's possible. But we've still weakened *this* argument, because this argument thought the premise about Monday somehow proved their conclusion. If it's not Monday, we've shown that their premise doesn't guarantee their conclusion.

good

[@randomguy1221]

Does anyone have any study or tutor help recommendations? I am god awful at these

[@lakhvirsingh-lm4kj]

Anything that has wings can fly is not a necessary assumption, we only need some things that has wings can fly. But i guess depends how we interpret all in this context as species or as numbers. It is confusing hope you can clear it up

[@LuminateLSAT]

See PT140.1.22 to see that the LSAT would consider "anything that has wings can fly" a necessary assumption. Is there something about the way I explained it in the video that you disagree with? If "anything that has wings can fly" were not true, then the premise is not sufficient to prove that pigs can fly. This is why "anything that has wings can fly" is necessary for the argument. It's necessary in order for the premise to be enough to guarantee the conclusion.

[@lakhvirsingh-lm4kj]

@@LuminateLSAT this question puzzled me when a took that PT as well. Could you please elaborate how can something which can be negated and conclusion in the stimulus still follows could be necessary. My assumption was that if we negate something and conclusion cannot follow anymore that is necessary. I would really. Appreciate your clarification on this issue. Thanks so much Kevin.

[@lakhvirsingh-lm4kj]

@@LuminateLSAT wouldn’t conclusion still follow if we assume atleast some things which has wings can fly. That is why i was confused that Anything might not be necessary because it can be negated and the conclusion still follows. Let me know if i am mistaken here Kevin please.

[@LuminateLSAT]

@@lakhvirsingh-lm4kj It looks like you think that the negation of a necessary assumption needs to disprove the conclusion. That's not correct. The negation just needs to show that the premise cannot guarantee the conclusion. If we negate "anything that has wings can fly," then the premise offered -- pigs have wings -- cannot, by itself, guarantee the conclusion anymore. That weakens the argument, which means the argument must assume "anything that has wings can fly." You're right that the conclusion could still be true -- it's still possible that pigs can fly even if some things with wings cannot fly. But the key point is that if you negate "anything that has wings can fly," the given premise cannot guarantee that pigs can fly. The negation of a necessary assumption just needs to show that premise cannot guarantee the conclusion -- it doesn't need to show that the conclusion is impossible to be true.

[@andresfernades2481]

I still don’t understand why “anything that has wings can fly” is a necessary assumption. Why do we need to assume that everything with wings can fly when all we need is that some things with wings can fly? I understand that is sufficient definitely, but necessary? I still have trouble with grasping that.

[@LuminateLSAT]

Every argument assumes that its premises are enough to prove the conclusion. "Penguins have wings. So, they can fly." In this argument, the only premise I have put forward is that penguins have wings. If I think this premise allows me to conclude that they can fly, that means I must believe that if something has wings, then they can fly. If I did not believe this, then I would not be able to draw the conclusion that penguins can fly merely from the premise that they have wings. So, I am truly assuming that anything that has wings can fly (this is another way of saying "If wings, then fly"). Imagine if the statement "anything that has wings can fly" were false. That would mean the fact something has wings does not automatically prove it can fly. If that's the case, how can I put forth the premise that penguins have wings and believe that this premise, by itself, allows me to conclude that penguins can fly? If there's a possibility that some things with wings *cannot* fly, then my premise is not enough to prove the conclusion. Note how the assumption would change if I changed the premises of the argument: "Since penguins are birds and they have wings, they must be able to fly." Here, I'm giving you 2 reasons penguins can fly: they are birds and have wings. (I'm not longer just relying on the fact that they have wings.) That means I'm assuming, "If something is a bird AND it has wings, then it can fly." I'm no longer assuming that *anything* that has wings can fly. I'm only assuming that anything that is both a bird and has wings can fly.

[@andresfernades2481]

⁠@@LuminateLSATthank you so much! This is incredibly helpful! No one explains LR as clearly and precisely as you do!

[@lraoux]

“In his physics class, Timmy worked hard only on assignments that were graded.” I disagree about this being a necessary assumption. Hypothetically, if this were a multiple choice test (as is the LSAT), Timmy could have guessed on every answer, gotten them right, and never have worked hard on any of the assignments that were graded. Or maybe this could have been a class where *nobody* was truly interested (including Timmy), and he just happened to get the highest score in spite of not working on assignments that were graded. I therefore consider it a sufficient assumption. Thoughts?