I'm understanding this but I think that it would be far easier to learn if you would use acronyms that match what is being discussed in the arguments rather than always using A, B, C.
If most comes before all, it is valid; if most comes after all, it is invalid.
This makes sense because if you say
Premise: All lawyers are smart people. Most smart people enjoy coffee.
Conclusion: Some lawyers enjoy coffee.
In lawgic:
lawyer --> smart ‑m→ enjoy coffee
From this, you cannot infer that some lawyers enjoy coffee because we don't know how big the set of lawyers and smart people is. It can be that there are 300 lawyers, all of whom are smart, but an overall total of 1,000 smart people - so there is still 700 smart people who could enjoy coffee and 300 who happen to be the lawyers who don't enjoy it. This makes the statement that most smart people enjoy coffee still stand but not the inference that some lawyers enjoy coffee. So, it can be the case that no lawyer at all enjoys coffee. This invalid argument boils down to the idea that we are unsure how big the set for the first two sets is.
An example of this argument in a valid way would be
Premise: Most lawyers are smart people. All smart people enjoy coffee.
Conclusion: Some lawyers enjoy coffee.
In lawgic:
lawyer ‑m→smart→enjoy coffee
From this, you can infer that some lawyers enjoy coffee. This is because we know that over 51% of lawyers are smart and ALL smart people enjoy coffee; therefore, it must be the case that SOME (at least one or all) lawyers do enjoy coffee because most of them (over half of them) fall in the set of being smart, all of whom enjoy coffee.
To break this down I like to think about it as numbers.
1st claim: Let's say there are 30 violinist at the NY Philharmonic that know how to play violin.
2nd claim: There are 1 million violinists in the entire world and more than 50% of them do not play the violin well.
Can we logically make the conclusion that the 30 violinists at the NY Philharmonic are part of the more than 50% of violinists who do not play violin well? Well no we cannot as doing so would require us to assume that the 30 violinists belong to the more than 50% group of violinist who do not play the violin well. The conclusion is based on an assumption that we cannot logically deduce or infer.
Here's some examples I made for myself, hope this provides some clarity!
Trap 4: Swapping "most" and "all" arrows
Remember: a valid conclusion about intersecting sets can only be made if the most arrow appears before the all arrow.
Ex.
All wrestlers in the WMMA know how to fight. Most people who know how to fight suck at it. Therefore, some fighters in the WMMA suck at it
WMMA -> F --m-> Suck@F
____
WMMA <-s-> Suck@F
The above is NOT a valid conclusion. The first set is not indicative of any other set, even if their qualities (fighting) overlap. So, that quality cannot be used to draw valid conclusions .
Ex.
Most WMMA women know how to fight. All women who know how to fight are strong. Therefore, most WMMA women are strong.
WMMA -m-> F -> S
____
WMMA -m-> S
The above conclusion IS valid
Remember, it's not "all most" chocolate is good, its "most all" chocolate is good
I don't want to "almost" ace the test, i want to get "most-all" questions correct
Agreed. This was difficult to understand. To clarify: if "know‑m→/good AND know→violinist at philharmonic" then the "most" arrow and "sufficiency/necessity" arrow cannot be used the same way the "some" arrow can be used. I.e. can't group together concepts and say "some of those who are /good are violinists at the philharmonic" that share a sufficient condition ("know") because of the unidirectionality of the arrow?
This made more sense when I remembered the question from the last skill builder:
"All surgeons enjoy the sight of blood. Most vampires enjoy the sight of blood."
I had incorrectly inferred that the "shared" concept of enjoying the sight of blood meant that the other groups (surgeons and vampires) also had overlap, and concluded that "Some surgeons are vampires."
That was wrong-- just because something enjoys the sight of blood, it does not mean they are either a surgeon, a vampire, or both. Enjoying the sight of blood is not necessary to be a surgeon or vampire.
This one took a while to understand. The way I understood it was:
All A belong to B.
Most B belong to C.
Therefore, some A belong to C.
This argument is invalid because the conclusion cannot be logically proven. We do not know whether any members of A are included among the majority of B that belong to C. It is possible that some A belong to C, but it is also possible that every member of A falls within the minority of B that does not belong to C.
Therefore, “some A belong to C” may be true, but the premises do not establish that it must be true. The overlap is possible, not guaranteed.
#feedback This section needs videos. It's difficult to process these with no diagrams, especially when the symbols used are simply "A," "B," and "C." I feel I am spending more time trying to remember which symbol represents which premise or conclusion instead of actually internalizing and understanding the concepts.
The “most” arrow must go before the “all.” Because, if you say all A-B and then "some" from B-C you can’t conclude A-C because we’re not sure that B carried over the portion of A to go into C. But if you do most A-B and all B-C we can conclude that A to C because it guarantees that all B went into C.
@Hnelson88 I have no problem people complaining, if anything it helps people like us... who are willing to do the work to be... what did the reading say? exceptionally good?
@Hnelson88 Everyone's situation is different. Personally, I study most days around 8:30pm, after working all day as a paralegal, and putting my two toddlers down for bed. I'm pretty exhausted every night... and the videos make it so much easier and faster.
While the example of the philharmonic painted a really good picture, I think the scoop analogy that was previously used really helped me understand this at a formal level.
If you put a big ol’ scoop of A into B and then a scoop of B into C, there will be some A in C. However, if you have a bucket of A then a bucket of B, and scoop from the B bucket into C, none of A will make it into C. Thinking of it like this really helped me understand the chain.
"However, if you have a bucket of A then a bucket of B, and scoop from the B bucket into C, none of A will make it into C. "
I think this is slightly inaccurate.
You pour a bucket of A into bucket B. (All Philharmonic know how to play violin)
You take a scoop from bucket B into C (Most that know how to play violin don't play well).
You take a look at bucket C and you CANNOT make a conclusion. Did the scoop we took include A? Who knows??? In the example, we don't know if the scoop from C includes A. In reality, it probably does not include any members of the philharmonic.
Writing one more example for good measure.
All Jets fans live in New York. Most of the people in New York like to go for runs. Therefore, some Jets fans go for runs.
Can we make a conclusion on our Bucket C (people that like to go for runs)? No! We cannot say with certainty that these include Jets fans. They could include anyone in New York who is a giants fan, or doesn't watch football, or likes opera, or [insert random detail] etc. In fact, in my experience, as a Jets fan, most Jets fans are out of shape and probably don't run (no offense to Jets nation).
Most who know how to play are not exceptionally good
Therefore, some at the NYP are not exceptionally good
This is giving us A -> B -m> C
So this is invalid as it's making C sufficient for A which is out of line with our diagram. For all we know there could be no violinists at NYP that aren't exceptionally good. This would lead to the argument being invalid as some is too vague and isn't supported
139 comments
@NoaF123 i would of just pictured the diagram to show that more than 50% of B is being consumed by C just to show that B-M->C
Thank you for the diagram!
@NoaF123 this was very helpful, thank you!
@NoaF123 very helpful! Now i understand it. Thank you
I'm understanding this but I think that it would be far easier to learn if you would use acronyms that match what is being discussed in the arguments rather than always using A, B, C.
+1 soooo confusing as ABC
#feedback
If most comes before all, it is valid; if most comes after all, it is invalid.
This makes sense because if you say
Premise: All lawyers are smart people. Most smart people enjoy coffee.
Conclusion: Some lawyers enjoy coffee.
In lawgic:
lawyer --> smart ‑m→ enjoy coffee
From this, you cannot infer that some lawyers enjoy coffee because we don't know how big the set of lawyers and smart people is. It can be that there are 300 lawyers, all of whom are smart, but an overall total of 1,000 smart people - so there is still 700 smart people who could enjoy coffee and 300 who happen to be the lawyers who don't enjoy it. This makes the statement that most smart people enjoy coffee still stand but not the inference that some lawyers enjoy coffee. So, it can be the case that no lawyer at all enjoys coffee. This invalid argument boils down to the idea that we are unsure how big the set for the first two sets is.
An example of this argument in a valid way would be
Premise: Most lawyers are smart people. All smart people enjoy coffee.
Conclusion: Some lawyers enjoy coffee.
In lawgic:
lawyer ‑m→smart→enjoy coffee
From this, you can infer that some lawyers enjoy coffee. This is because we know that over 51% of lawyers are smart and ALL smart people enjoy coffee; therefore, it must be the case that SOME (at least one or all) lawyers do enjoy coffee because most of them (over half of them) fall in the set of being smart, all of whom enjoy coffee.
Hopefully this breaks it down well enough.
Incredible explanation, thank you so much!
@susanatovar This is really helpful, the only thing is that at the bottom, when you write
lawyer ‑m→smart→enjoy coffee
... I believe it actually leads to MOST lawyers enjoy coffee, not just some lawyers enjoy coffee (ofc tho, some is contained within most).
"Most before all":
Premise: A —m→ B → C
Conclusion: A —m→ C)
This would benefit from having a video explanation, all the different terms and sets are a bit confusing.
#FEEDBACK We need the videos back
I am actually crying. I have no idea what this is saying
me. this is so confusing
I understood it with this analogy, maybe it'll help you:
Premise 1: All Olympic sprinters know how to run.
Premise 2: Most people who know how to run are not exceptionally fast.
Invalid conclusion: Therefore, some Olympic sprinters are not exceptionally fast.
To break this down I like to think about it as numbers.
1st claim: Let's say there are 30 violinist at the NY Philharmonic that know how to play violin.
2nd claim: There are 1 million violinists in the entire world and more than 50% of them do not play the violin well.
Can we logically make the conclusion that the 30 violinists at the NY Philharmonic are part of the more than 50% of violinists who do not play violin well? Well no we cannot as doing so would require us to assume that the 30 violinists belong to the more than 50% group of violinist who do not play the violin well. The conclusion is based on an assumption that we cannot logically deduce or infer.
Here's some examples I made for myself, hope this provides some clarity!
Trap 4: Swapping "most" and "all" arrows
Remember: a valid conclusion about intersecting sets can only be made if the most arrow appears before the all arrow.
Ex.
All wrestlers in the WMMA know how to fight. Most people who know how to fight suck at it. Therefore, some fighters in the WMMA suck at it
WMMA -> F --m-> Suck@F
____
WMMA <-s-> Suck@F
The above is NOT a valid conclusion. The first set is not indicative of any other set, even if their qualities (fighting) overlap. So, that quality cannot be used to draw valid conclusions .
Ex.
Most WMMA women know how to fight. All women who know how to fight are strong. Therefore, most WMMA women are strong.
WMMA -m-> F -> S
____
WMMA -m-> S
The above conclusion IS valid
Remember, it's not "all most" chocolate is good, its "most all" chocolate is good
I don't want to "almost" ace the test, i want to get "most-all" questions correct
Why not videos this is frustrating
#feedback please include a video for this lesson. It was so confusing
Agreed. This was difficult to understand. To clarify: if "know‑m→/good AND know→violinist at philharmonic" then the "most" arrow and "sufficiency/necessity" arrow cannot be used the same way the "some" arrow can be used. I.e. can't group together concepts and say "some of those who are /good are violinists at the philharmonic" that share a sufficient condition ("know") because of the unidirectionality of the arrow?
Where are the videos? I prefer the videos to just reading.
#feedback, put video for this section pls
This made more sense when I remembered the question from the last skill builder:
"All surgeons enjoy the sight of blood. Most vampires enjoy the sight of blood."
I had incorrectly inferred that the "shared" concept of enjoying the sight of blood meant that the other groups (surgeons and vampires) also had overlap, and concluded that "Some surgeons are vampires."
That was wrong-- just because something enjoys the sight of blood, it does not mean they are either a surgeon, a vampire, or both. Enjoying the sight of blood is not necessary to be a surgeon or vampire.
This one took a while to understand. The way I understood it was:
All A belong to B.
Most B belong to C.
Therefore, some A belong to C.
This argument is invalid because the conclusion cannot be logically proven. We do not know whether any members of A are included among the majority of B that belong to C. It is possible that some A belong to C, but it is also possible that every member of A falls within the minority of B that does not belong to C.
Therefore, “some A belong to C” may be true, but the premises do not establish that it must be true. The overlap is possible, not guaranteed.
#feedback This section needs videos. It's difficult to process these with no diagrams, especially when the symbols used are simply "A," "B," and "C." I feel I am spending more time trying to remember which symbol represents which premise or conclusion instead of actually internalizing and understanding the concepts.
Here is a rule of thumb that could help to understand this concept.
Most --> All chains can work.
All --> most chains don't preserve logic.
Hope this helps!
Hope this helps someone:
The “most” arrow must go before the “all.” Because, if you say all A-B and then "some" from B-C you can’t conclude A-C because we’re not sure that B carried over the portion of A to go into C. But if you do most A-B and all B-C we can conclude that A to C because it guarantees that all B went into C.
these formal logic flaws have been harder for me to grasp....hopefully it makes more sense in other examples 🥲
Need Videos here so confusing to read it
where are the videos I dont like reading 😠
Has anybody found an actual LSAT question where this flaw is done, so we can see how the answers would look?
Amazing we’re training for the LSAT and people are complaining about having to read
@Hnelson88 I have no problem people complaining, if anything it helps people like us... who are willing to do the work to be... what did the reading say? exceptionally good?
@Hnelson88 Everyone's situation is different. Personally, I study most days around 8:30pm, after working all day as a paralegal, and putting my two toddlers down for bed. I'm pretty exhausted every night... and the videos make it so much easier and faster.
Adding this into the comment thread as this is what helped me understand this lesson since there are no videos:
Think:
❌ All → Most = “leakage”
You lose track of A
Nothing guaranteed
✅ Most → All = “capture”
Some A gets picked
Then ALL of them get carried forward
Thanks Chatgpt.
#feedback would it be possible to get a video for this?
While the example of the philharmonic painted a really good picture, I think the scoop analogy that was previously used really helped me understand this at a formal level.
If you put a big ol’ scoop of A into B and then a scoop of B into C, there will be some A in C. However, if you have a bucket of A then a bucket of B, and scoop from the B bucket into C, none of A will make it into C. Thinking of it like this really helped me understand the chain.
"However, if you have a bucket of A then a bucket of B, and scoop from the B bucket into C, none of A will make it into C. "
I think this is slightly inaccurate.
You pour a bucket of A into bucket B. (All Philharmonic know how to play violin)
You take a scoop from bucket B into C (Most that know how to play violin don't play well).
You take a look at bucket C and you CANNOT make a conclusion. Did the scoop we took include A? Who knows??? In the example, we don't know if the scoop from C includes A. In reality, it probably does not include any members of the philharmonic.
Writing one more example for good measure.
All Jets fans live in New York. Most of the people in New York like to go for runs. Therefore, some Jets fans go for runs.
Can we make a conclusion on our Bucket C (people that like to go for runs)? No! We cannot say with certainty that these include Jets fans. They could include anyone in New York who is a giants fan, or doesn't watch football, or likes opera, or [insert random detail] etc. In fact, in my experience, as a Jets fan, most Jets fans are out of shape and probably don't run (no offense to Jets nation).
great analogy!
I'll add my input-
To simplify the violinist argument consider this:
All violinists at NYP know how to play
Most who know how to play are not exceptionally good
Therefore, some at the NYP are not exceptionally good
This is giving us A -> B -m> C
So this is invalid as it's making C sufficient for A which is out of line with our diagram. For all we know there could be no violinists at NYP that aren't exceptionally good. This would lead to the argument being invalid as some is too vague and isn't supported
Does anyone else draw Venn Diagrams for these problems? It makes so much more sense when you can just visualize the buckets.
@Jurcis Yes I agree. When I think of the venn diagrams, it all comes into place!
@Jurcis 6 months late, but I also use venn diagrams and they help a lot!