C is the correct answer because it is better than any of the other answers, but it is not a necessary assumption for the argument. The rule premise, fact premises, and conclusion in the stimulus are about books that recommend composting. Answer C is about any explanation of composting. Lets posit that there exists an explanation that does not recommend composting but does mention it, and gives a basic explanation. That explanation does not include any information about the difference between hot and cold composting. This explanation would violate the rule in answer choice C, but not create any issue with the argument. In formal logic, let RC be recommends compost, EB be explains the basics, EHC be explain the difference between hot and cold. Choice C says for all x, EB(x) -> EHC(x), which we contrapose to ~EHC(x) -> ~EB(x). It is sufficient to make the argument valid. The narrower answer that would be both necessary and sufficient is forall x (RC(x) ^ EB(x)) -> EHC(x), which we contrapose and apply DeMorgan to get ~EHC(x) -> (~RC(x) OR ~EB(x)). This is entirely consistent with natural expectations about what "the basics" mean. The meaning of "basics" depends on the scope. If you're recommending that someone use compost, the basics might be more than if you're just mentioning that compost exists, perhaps to a curious 6 year old who is wondering about the stinky stuff being spread over some field. There the basics might be that compost has nutrients for plants, and sometimes uses smelly things like animal poop. There, you might miss the basics if you didn't explain the smell, but would never be expected to explain hot vs cold composting.
Writing this for my own benefit, but the mistake in intuition I made was thinking necessary assumptions should be making the conclusion incorrect, but they're making the argument incorrect. C) does not make the idea "any gardening book that does not explain the basics is flawed" impossible, since there could be some other basic. But it does make the argument incorrect, since there's no basis in the premises for the conclusion.
@ArthurWhite I'm not completely sure if this is the flaw, but I notice you say flawed is sufficient to a book being published by GPP. This is not true, since only some books by GPP recommend adding compost and don't explain h&c difference, and any gardening book that does not explain the basics of composting is flawed, so therefore some books by GPP are flawed. Yes these books by GPP are flawed, but that does not mean all flawed books are published by GPP. The stimulus doesn't say that these books are the only gardening books in the world that recommend adding compost but don't explain h vs c. So it is not sufficient to assume that because a book is flawed it must have been published by GPP. But your statement right after this, statement 6, is only correct in the reverse, and I think you could have simplified this for yourself by making that assumption right off that bat because you can see that if a book is flawed, it doesn't explain the basics of composting, so these books are flawed. The conclusion is saying they are flawed because any book that doesn't explain the basics of composting is flawed. Therefore it is saying these books recommend composting but do not explain the basics of composting. All we know about what these books contain about composting is that they recommend composting but do not explain the difference between h&c. So it must be true that if a book does not explain the difference between h&c, it does not explain composting. Therefore not explaining the difference between hot and cold composting is sufficient to not explaining the basics of composting. So basically hot and cold composting is a basic of composting. However, there could theoretically be other basics of composting. We don't know if these are explained in the book or not but we don't honestly care. We just know that because it doesn't explain h&c composting, it doesn't explain the basics. If we look at answer choice D, it says "everyone" who understands the difference between h&c composting understands the basics of composting. But we don't know if there are other basics of composting. We just know that h&c composting is a basic of composting, because a book that didn't explain h&c did not explain the basics. But even if the book explained h&c, we don't know if it would still be considered flawed because we don't know if that is actually a sufficient assumption to explaining the basics of composting, we just know that it is necessary to explaining the basics of composting, because without it, we did not explain the basics. So looking at answer choice C, an explaination of the basics of composting must include an explaination of the difference between hot and cold composting, this is in fact a necessary assumption because without explaining h&c composting, a book fails to explain the basics of composting. Sorry this is so long but to sum up, the issue I'm seeing is you assumed that explaining hot and cold composting is sufficient to explaining the basics of composting, but the argument doesn't say this. It just says that without explaining hot vs. cold composting, we haven't explained the basics. there could be other basics, but we know h vs c is one of them. So D is wrong because someone totally could understand h vs c composting but still not understand the basics of composting because there may be other basics of composting we have no idea about. Hope this helped but reply if not bc I don't think I'm great at explaining things.
#feedback A lot of these sample questions are not available to preview (the small eye icon) so that we can try answering them on our own before watching the video, like they were in the older 7sage website. Would it be possible to add this option again? It's very helpful. Thank you
Its confusing that he relies so much on past lessons and refers to them often because I'm sure I'm not the only one who wanted to start with necessary assumption before sufficient and because in the lessons sufficient came first he keeps referring to it and its really throwing me off.
@alzayadi444 I too think it's good to do them in order. Him bringing in past lessons actually strengthens our understanding by making the connection of the new with the old, its very good for learning complex concepts (I'm a HS Science Teacher), so def take advantage of his connections by going in order !
The argument really is missing a very important connection in order for the conclusion to follow logically. The conclusion says "some books published by GP are flawed", because P1 they don't explain the difference between hot and cold composting and P2 a gardening book that recommends adding compost needs to explain at least the basics of composting. See how there's an assumption that NEEDS to be made to conclude that some books published by GP are flawed? Explaining the difference between hot and cold composting needs to be (in part or fully) the basics of composting. This is exactly what answer c says, answer e is just saying not flawed gardening book→includes an explanation of at least the basics of composting but that does not help the conclusion follow logically. It is very important to identify the conclusion because that is what you need to strengthen.
Can someone explain how the negation of "/explain H and C -> /explain basics" translates to "/explain H and C AND explain basics"? Wouldn't the contrapositive just go back to the original answer? #feedback
@TaniaP. negation of a conditional (ex. P-->Q) is to get the sufficient condition and keep it, while adding a conjunction/AND and negating the necessary condition.
So negation of (/explain H and C ---> /explain basics) is:
/(explain H and C) AND (explain basics)
You might wonder why negating the necessary resulted in removing the negation and leaving us with (explain basics). That is because it was already negated and double negating just cancels out the negation. For instance: explaining basics is logically equivalent to //explaining basics.
It's flipped sufficiency and necessity. We can only conclude the other way around that a book is flawed if it talks about composting and the basics. Even if a book does contain these, it can still be flawed, such as if it teaches something entirely false on a different aspect of gardening.
Moreover, is just that the argument really is missing a very important connection in order for the conclusion to follow logically. The conclusion says "some books published by GP are flawed", because P1 they don't explain the difference between hot and cold composting and P2 a gardening book that recommends adding compost needs to explain at least the basics of composting. See how there's an assumption that NEEDS to be made to conclude that some books published by GP are flawed? Explaining the difference between hot and cold composting needs to be (in part or fully) the basics of composting. This is exactly what answer c says, answer e is just saying not flawed gardening book→includes an explanation of at least the basics of composting but that does not help the conclusion follow logically. It is very important to identify the conclusion because that is what you need to strengthen.
I thought negation meant switching the SC and the NC and then negating them. So how is the negation of explanation of basics → explanation of hot vs. cold
explanation of hot v. cold and explanation of basics
This helped me understand the difference between NA and SA
Say you are buying something that costs $1, it is necessary for you to have the value of 1 cent, but 1 cent is not sufficient. If you have the value of $100, that is sufficient for purchasing the $1 item, but not necessary.
SA and NA overlap if you have exactly $1. $1 is both necessary and sufficient to purchase the item.
When looking at the argument's subject, and then the answer choice's subject, is it almost always going to match up? Like in this video, the subject being the book?
I have been so confused on the difference of NA and SA but the analogy that made me clearly understand is this...
A Necessary Assumption (NA) is like life support that keeps a patient alive. It gives the argument a chance to be true, but doesn't guarantee it, as other issues could still arise.
A Sufficient Assumption (SA) is like saying that as long as the patient is on life support, nothing can kill them. This guarantees the argument's conclusion, making it unbreakable.
In summary, an NA keeps the argument viable but not guaranteed, while an SA ensures the argument is conclusive.
in the most simplified way possible Iv'e come to understand NA as the fact that must the true for the argument to make sense could someone please confirm or deny wether this is a correct way to think about it?
i've heard SA being described as a super strengthener and NA as a weak strengthener. Also, yes it must be true, because part of the strategy of negating is that making the statement false would not bring about the intended conclusion :)
This is correct, as long as you interpret "for the argument to make sense" as "for the given premises to provide support to the conclusion." If the necessary assumption is not true, then the argument shouldn't make sense anymore, or in other words, the given premises will not support the conclusion.
This is an OK way to understand SA and NA, but I would want you to recognize that there are quite a few examples of NA that are also SA. So, you will find strongly worded NA; it's just that NA doesn't tend to require a strong answer, whereas SA almost always requires a strong answer.
The reading before this really helped me understand this question right away, I'm finally starting to visualize the right answers before they are even shown.
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56 comments
is it always the case that irrelevant answers on NA questions will fail to strengthen the argument AND fail to weaken the argument?
C is the correct answer because it is better than any of the other answers, but it is not a necessary assumption for the argument. The rule premise, fact premises, and conclusion in the stimulus are about books that recommend composting. Answer C is about any explanation of composting. Lets posit that there exists an explanation that does not recommend composting but does mention it, and gives a basic explanation. That explanation does not include any information about the difference between hot and cold composting. This explanation would violate the rule in answer choice C, but not create any issue with the argument. In formal logic, let RC be recommends compost, EB be explains the basics, EHC be explain the difference between hot and cold. Choice C says for all x, EB(x) -> EHC(x), which we contrapose to ~EHC(x) -> ~EB(x). It is sufficient to make the argument valid. The narrower answer that would be both necessary and sufficient is forall x (RC(x) ^ EB(x)) -> EHC(x), which we contrapose and apply DeMorgan to get ~EHC(x) -> (~RC(x) OR ~EB(x)). This is entirely consistent with natural expectations about what "the basics" mean. The meaning of "basics" depends on the scope. If you're recommending that someone use compost, the basics might be more than if you're just mentioning that compost exists, perhaps to a curious 6 year old who is wondering about the stinky stuff being spread over some field. There the basics might be that compost has nutrients for plants, and sometimes uses smelly things like animal poop. There, you might miss the basics if you didn't explain the smell, but would never be expected to explain hot vs cold composting.
Writing this for my own benefit, but the mistake in intuition I made was thinking necessary assumptions should be making the conclusion incorrect, but they're making the argument incorrect. C) does not make the idea "any gardening book that does not explain the basics is flawed" impossible, since there could be some other basic. But it does make the argument incorrect, since there's no basis in the premises for the conclusion.
Answer choices that bridge conditional gaps between the premises and conclusion are necessary, so (C) is necessary.
Question... on the actual LSAT will I be able to write on the question like so:
necessary assumption keeps it alive, sufficient assumption makes it invincible
Would someone correct my conditional logic steps that may lead to the condition that forms the answer:
P1: "some gardening books published by Garden Path recommend tilling the soil and adding compost before starting a new garden on a site"
(domain) gardening books:
published by GPP <-s-> tilling AND compost (1)
P2: "they (those same books) do not explain the difference between hot and cold composting."
published by GPP <-s-> / diff H&C composting (2)
P3: "any gardening book that recommends adding compost is flawed if it does not explain at least the basics of composting"
(domain) gardening books :
/ basics composting -> flawed (3)
Conclusion: "some books published by Garden Path are flawed."
published by GPP <-s-> flawed (4)
(4) is the same as :
flawed <-s-> published by GPP (5)
combining (5) and (2)
flawed <-s-> published by GPP <-s-> / diff H&C composting (6)
based off of (6)
flawed <-s-> / diff H&C composting (7) [NOTE: I realize we cannot do that due to the <s> relationship not being transitive, but how else to proceed?]
Combine (7) and (3)
/ basics composting ->/ diff H&C composting
contrapositive:
diff H&C composting -> basics composting
Based on the above D should be the answer perhaps?
Though certainly there is a flaw in there somewhere particularly with the <s> relationships inference etc.
@ArthurWhite I'm not completely sure if this is the flaw, but I notice you say flawed is sufficient to a book being published by GPP. This is not true, since only some books by GPP recommend adding compost and don't explain h&c difference, and any gardening book that does not explain the basics of composting is flawed, so therefore some books by GPP are flawed. Yes these books by GPP are flawed, but that does not mean all flawed books are published by GPP. The stimulus doesn't say that these books are the only gardening books in the world that recommend adding compost but don't explain h vs c. So it is not sufficient to assume that because a book is flawed it must have been published by GPP. But your statement right after this, statement 6, is only correct in the reverse, and I think you could have simplified this for yourself by making that assumption right off that bat because you can see that if a book is flawed, it doesn't explain the basics of composting, so these books are flawed. The conclusion is saying they are flawed because any book that doesn't explain the basics of composting is flawed. Therefore it is saying these books recommend composting but do not explain the basics of composting. All we know about what these books contain about composting is that they recommend composting but do not explain the difference between h&c. So it must be true that if a book does not explain the difference between h&c, it does not explain composting. Therefore not explaining the difference between hot and cold composting is sufficient to not explaining the basics of composting. So basically hot and cold composting is a basic of composting. However, there could theoretically be other basics of composting. We don't know if these are explained in the book or not but we don't honestly care. We just know that because it doesn't explain h&c composting, it doesn't explain the basics. If we look at answer choice D, it says "everyone" who understands the difference between h&c composting understands the basics of composting. But we don't know if there are other basics of composting. We just know that h&c composting is a basic of composting, because a book that didn't explain h&c did not explain the basics. But even if the book explained h&c, we don't know if it would still be considered flawed because we don't know if that is actually a sufficient assumption to explaining the basics of composting, we just know that it is necessary to explaining the basics of composting, because without it, we did not explain the basics. So looking at answer choice C, an explaination of the basics of composting must include an explaination of the difference between hot and cold composting, this is in fact a necessary assumption because without explaining h&c composting, a book fails to explain the basics of composting. Sorry this is so long but to sum up, the issue I'm seeing is you assumed that explaining hot and cold composting is sufficient to explaining the basics of composting, but the argument doesn't say this. It just says that without explaining hot vs. cold composting, we haven't explained the basics. there could be other basics, but we know h vs c is one of them. So D is wrong because someone totally could understand h vs c composting but still not understand the basics of composting because there may be other basics of composting we have no idea about. Hope this helped but reply if not bc I don't think I'm great at explaining things.
#feedback A lot of these sample questions are not available to preview (the small eye icon) so that we can try answering them on our own before watching the video, like they were in the older 7sage website. Would it be possible to add this option again? It's very helpful. Thank you
Necessary = a portal that must be open, but doesn't guarantee arrival.
It’s like a required checkpoint — if it’s closed, you can’t go through.
Must be true for the argument to work at all.
Sufficient = a specific path that directly drops you at the goal.
It’s like stepping on a teleportation pad that guarantees you arrive at the conclusion.
Proves the conclusion is true.
Its confusing that he relies so much on past lessons and refers to them often because I'm sure I'm not the only one who wanted to start with necessary assumption before sufficient and because in the lessons sufficient came first he keeps referring to it and its really throwing me off.
#feedback
I did the same thing, it is really helpful to do most of the stuff in order. The curriculum is rly made to be done (mostly) in order.
@Deybomb17 I agree. If you do it in the way the course is set out, it becomes easier to understand because it builds the foundations he refers to.
@alzayadi444 I too think it's good to do them in order. Him bringing in past lessons actually strengthens our understanding by making the connection of the new with the old, its very good for learning complex concepts (I'm a HS Science Teacher), so def take advantage of his connections by going in order !
What are all the types of reasoning?
There's rule-application, conditional, causal... Is that it?
Also reasoning by analogy and cost-benefit analysis
The argument really is missing a very important connection in order for the conclusion to follow logically. The conclusion says "some books published by GP are flawed", because P1 they don't explain the difference between hot and cold composting and P2 a gardening book that recommends adding compost needs to explain at least the basics of composting. See how there's an assumption that NEEDS to be made to conclude that some books published by GP are flawed? Explaining the difference between hot and cold composting needs to be (in part or fully) the basics of composting. This is exactly what answer c says, answer e is just saying not flawed gardening book→includes an explanation of at least the basics of composting but that does not help the conclusion follow logically. It is very important to identify the conclusion because that is what you need to strengthen.
Can someone explain how the negation of "/explain H and C -> /explain basics" translates to "/explain H and C AND explain basics"? Wouldn't the contrapositive just go back to the original answer? #feedback
Negation and contrapositive are two different things.
Conditional: P → C
Contrapositive: /C → /P
Inverse: /P → /C
Converse: C → P
Negation: P and /C
@TaniaP. negation of a conditional (ex. P-->Q) is to get the sufficient condition and keep it, while adding a conjunction/AND and negating the necessary condition.
So negation of (/explain H and C ---> /explain basics) is:
/(explain H and C) AND (explain basics)
You might wonder why negating the necessary resulted in removing the negation and leaving us with (explain basics). That is because it was already negated and double negating just cancels out the negation. For instance: explaining basics is logically equivalent to //explaining basics.
Could someone explain why E is wrong?
It's flipped sufficiency and necessity. We can only conclude the other way around that a book is flawed if it talks about composting and the basics. Even if a book does contain these, it can still be flawed, such as if it teaches something entirely false on a different aspect of gardening.
Moreover, is just that the argument really is missing a very important connection in order for the conclusion to follow logically. The conclusion says "some books published by GP are flawed", because P1 they don't explain the difference between hot and cold composting and P2 a gardening book that recommends adding compost needs to explain at least the basics of composting. See how there's an assumption that NEEDS to be made to conclude that some books published by GP are flawed? Explaining the difference between hot and cold composting needs to be (in part or fully) the basics of composting. This is exactly what answer c says, answer e is just saying not flawed gardening book→includes an explanation of at least the basics of composting but that does not help the conclusion follow logically. It is very important to identify the conclusion because that is what you need to strengthen.
I'm retaining NONE of this. Time for a break. Oh boy. I can only take so much butt kicking.
I thought negation meant switching the SC and the NC and then negating them. So how is the negation of
explanation of basics→ explanation of hot vs. coldexplanation of hot v. cold and explanation of basics
?
Negation is creating the logical opposite, what you said in the first sentence (switching the SC and NC and then negating) is the contrapositive
This helped me understand the difference between NA and SA
Say you are buying something that costs $1, it is necessary for you to have the value of 1 cent, but 1 cent is not sufficient. If you have the value of $100, that is sufficient for purchasing the $1 item, but not necessary.
SA and NA overlap if you have exactly $1. $1 is both necessary and sufficient to purchase the item.
Hope this helps someone as much as it helped me!
creds: https://www.youtube.com/watch?v=TjjkE6KGgb4
When looking at the argument's subject, and then the answer choice's subject, is it almost always going to match up? Like in this video, the subject being the book?
I have been so confused on the difference of NA and SA but the analogy that made me clearly understand is this...
A Necessary Assumption (NA) is like life support that keeps a patient alive. It gives the argument a chance to be true, but doesn't guarantee it, as other issues could still arise.
A Sufficient Assumption (SA) is like saying that as long as the patient is on life support, nothing can kill them. This guarantees the argument's conclusion, making it unbreakable.
In summary, an NA keeps the argument viable but not guaranteed, while an SA ensures the argument is conclusive.
I really like this analogy!
in the most simplified way possible Iv'e come to understand NA as the fact that must the true for the argument to make sense could someone please confirm or deny wether this is a correct way to think about it?
i've heard SA being described as a super strengthener and NA as a weak strengthener. Also, yes it must be true, because part of the strategy of negating is that making the statement false would not bring about the intended conclusion :)
This is correct, as long as you interpret "for the argument to make sense" as "for the given premises to provide support to the conclusion." If the necessary assumption is not true, then the argument shouldn't make sense anymore, or in other words, the given premises will not support the conclusion.
This is an OK way to understand SA and NA, but I would want you to recognize that there are quite a few examples of NA that are also SA. So, you will find strongly worded NA; it's just that NA doesn't tend to require a strong answer, whereas SA almost always requires a strong answer.
Thank you for the clarification
https://7sage.com/lsat_explanations/lsat-64-section-3-question-12/
The reading before this really helped me understand this question right away, I'm finally starting to visualize the right answers before they are even shown.
Damn. You're levelling up. That is the point that great LSAT takers reach. Congrats!
JY still the best teacher even with a sore throat
For the correct Answer choice C , when you did the contrapositive of the AC its like a MBT, because that contrapositive is supported by the stimulus
( the chain you did
/explain basics ---> flawed. #feedback
Adding to this, but its a MBT question in disguise
SA has made me feel fully defeated, hope to redeem myself with NA
im hoping to come back like the 2016 cavaliers in the nba finals after sa questions
mood