Conditional Logic | LSAT Logical Reasoning
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- Опубліковано 12 сер 2024
- Knowing how to correctly interpret, diagram, and manipulate conditional logic only impacts about 20% of questions, but it often impacts 50% or more of students' most fixable errors.
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I have been studying with 7sage, The Bibles and Khan Academy and this was the best explanation of conditional logic i've seen thus far. Thank you!
Awesome, glad it was helpful!
I have read through textbooks, online forums, and used several online tools such as law hub and kahn academy to study logical reasoning and I wasn't able to wrap my head around conditional logic until I watched this video. Thank you SO MUCH for making this video, it was extremely helpful!
This is the best Conditional Logic LSAT video, take that Powerscore and take that Elemental Prep, I can only imagine how much effort it went in to create these videos, thanks man!
I literally paid $1,000 for Test Masters. I love the program of Test Masters. It really helps me understand a lot but this thing here is next-level superiority. These lessons are insane.
this video is such a good refresher for the LSAT I cannot recommend it enough, boosted my practice score by 7 points!
this is the hardest part of the LSAT!
conditionals... facts
This is by far my favorite video for conditional logic - I seriously cannot thank you enough for how you broke this down. Exactlyy what I needed!!
These videos are truly saving me oh my goodness. Truly thank you folks for all your work in making these!
Thank you for a very informative and concise video! I am preparing for the Law Aptitude Exam of one of the top law schools in the Philippines and I understood the topic clearly even though it's my first time encountering conditionals. Also, your voice is very calming so it's a plus!
Amazing video. Clear and concise. Thank you.
For practice #5, "real men never shy away from yogurt," why is "never" considered to be universal and not a guarantee word? The word never is the opposite of always, which is placed under the guaranteed category. Why is it, then, that "never" is considered a universal category whereas "always" is a "guarantee?"
The reason why I'm asking is because guaranteed words are placed on the right, whereas universals are placed the left.
Thanks so much for this video. It is gold!
Hey-hey. I think you have a good point. "Never" would belong in the list of GUARANTEE words like "always". The word 'never' doesn't show up much on the test, so that's why it wasn't in any of the lists.
"Never" is NOT a universal; it's not a sufficient indicator.
In "real men never shy away from yogurt", the way I explain it is that it's a UNIVERSAL statement about "real men". We're generalizing about all real men, so "real men" is the sufficient trigger.
We could alternatively look at that sentence and say that "never" guarantees that the end of the sentence *doesn't* apply to real men.
With many (if not most) conditionals, we could alternatively talk about it as dealing with a Universal, Guarantee, or Requirement. It's can just be an arbitrary personal choice which one feels most salient to us.
But you're right that since I put the word "never" in bold/blue on the slides, I should have really explained it as a guarantee based on the word "never".
I explain it more as a variation on "No A's are B". That's a universal statement about A's. But we could equivalently express it by saying "A's are never B".
Like everyone said THANK YOU!! I appreciated this explanation so much! (just having trouble with bi-conditionals) but WOW!
Outstanding....no words to appreciate
What a video OMG...... I was crying for days 😢😢😢😢
This was SO helpful. Thank you!!
THANK YOU THANK YOU THAAAANKKKL YOUU FOR THIS VIDEO. SERIOUSLY IT IS THE BEST VIDEO ABOUT CONDITIONAL STATEMENTS!
Thank you for the high praise!
And by 'high' I mean "UPPERcase". :)
I was going over the Elemental Prep loophole book (pg 128 if interested) and was on this topic regarding either/or statements, ie, either A or B will happen. The book states to handle this as not A --> B with a contrapositive of not B --> A. But it makes more complete logical sense to me that this would be a biconditional of Anot B with its contrapositive being not A B. Using a biconditional, you more fully cover all cases... not just if you don't have a thing then it's the other thing but also if you have a thing then you don't have the other thing. Can someone explain to me why I'm wrong?
For #5, "Unless you apologize, I'm going to quit the game" I initially answered:
- If quit --> NO Apology
- If Apology --> NO quit
I see how the first one doesn't work, because the person could still quit in another situation, therefore "No Apology" is not REQUIRED for quitting. But the contrapositive, which translates to, "If you apologize then I don't quit," is something I'm snagging on. Is it because not quitting is not necessary for an apology? Thank you!
Many thanks for this video
Question: How do you know when to use contrapositives? Do you use them in every time you read a stimulus for logical reasoning sections?
Like a lot of things on LSAT, the more practice questions you experience, the better your intuitive spidey-sense becomes for when it's worth contraposing.
When you're first learning conditional logic, it's wise to always contrapose (I'm talking untimed practice here, not timed stuff), because your first goal is to make the act of contraposing such an automatic, braindead reflex that you would never need to write it down because you can effortlessly think it. That'll take some time. You can judge your progress by whether there's any lagtime or effort when you go to think/write the contrapositive. It's sort of like learning to say the alphabet backwards, only it takes longer. If you tried to say the alphabet backwards 5 times in a row, you'd find that you have to go slowly and focus the first couple times, and then you start to pick up speed, and by the 5th or 6th time you might feel yourself hitting more of the weird moments automatically.
Once you've got the ability to contrapose easily on a whim, then here would be the top list I can think of for when you want to do so:
1. You're reading a stimulus with multiple conditionals, and you need to contrapose in order to get rules with overlapping concepts to chain together (if they're already chained together, because one flows into the next within the paragraph, then no need).
2. If you're doing Inference questions and you're given a conditional chain, they love to test us on the contrapositive, so if you don't trust yourself to see the contrapositive chain in your head, then it would be worth writing.
3. If you're doing Sufficient Assumption or Principle-Strengthen (or some examples of Necessary Assumption) then you're likely to have conditional logic answers, and frequently the correct answer is disguised in the contrapositive form, so you want to be ready/willing to contrapose conditional answers.
4. In both Principle questions and Assumption questions, you're always trying to get a conditional to show Evidence ideas in the trigger and Conclusion language in the outcome (or in the case of some Assumption questions that deal with other reasoning moves, you want to make sure that the thing the author has established is on the left side, and the place the author is trying to go with that idea is on the right side). Again, ties back to #3, that answers may be in contrapositive form, and part of how you'd realize you should contrapose is by thinking, "Wait this answer has conclusion-y language on the left side of the arrow. Let me contrapose so that it's on the right side, so that I can better judge this answer."
5. When the stimulus is providing us with a principle, we want the judgy / normative language (should / shouldn't / ought / justified / good / bad / permissible / etc.) to be on the right side. So if needed, we contrapose the principle we're given so that we have what feels like CRITERIA on the left and what feels like a JUDGMENT on the right.
Thank You for this Video!
Thank you for this!
Very helpful!!! Thank you!
Hi LSAT Lab. I am a huge fan of yours. I was wondering why "and" becomes "or" when we convert a given statement into a contrapositive (4mins,38 seconds)
Think through the common sense of some true conditional statements.
For example, "If you're in Los Angeles, then you're in California and in the United States"
LA --> CA and USA
Suppose I told you Bob is in California. Does that tell you whether he's in LA?
Of course not. We can't read these backwards. He could be anywhere in CA.
Suppose I told you that Bob is NOT in California. Does that tell you whether he's in LA?
Sure! If he's not in CA, then we know he's not in LA.
So
~CA -- > ~LA
is valid all by itself
Similarly, if I told you Bob is not in the USA, then you would know for sure that he's not in LA.
So
~USA --> ~LA
is also valid all by itself
That's why we're getting
~CA or ~USA --> ~LA
Either one of those facts in the trigger is enough to guarantee that someone isn't in LA.
Writing it with an AND
~CA and ~USA --> ~LA
would suggest that we don't know whether someone is in LA until we've both heard that they're not in California and heard that they're not in the US.
Here's another real world conditional statement:
"You're allowed to see an R-rated movie only if you are at least 17 years old or with a parent/guardian".
Can see R-rated --> 17+ or With Guardian
If I tell you that Bob is younger than 17, does that tell you whether he's allowed to be in this R-rated movie?
No, because he might be allowed if he's with a guardian.
It's not fair to say
~17+ --> can NOT see R-rated
because some people who are under 17 can still the R-rated movie (if they're with a guardian).
Similarly you can't say
~With Guardian --> Can't see R-rated
because someone might be not with their parent/guardian, but be 25 years old, so they can still see the movie.
It's only when BOTH things don't happen that I know you can't see the movie.
Once I know you're NOT at least 17 and NOT with a guardian, then I can say you can't see the movie.
could number 8 also be written as:
- If BS and NOT M --> Cool
- If NOT Cool --> NOT BS or M
or is it better if breath strips and mints are kept as a single entity in the exercise?
You keep saying "put the main idea on the left or right" but I'm having trouble figuring out which of the two is the "main idea" that needs to be correctly placed. In fact, I keep getting it backward!
Thanks for the vids, I’m confused with gurantees and Causal agreements ( is it that the words will be strong when used in gurantees?)
A causes B vs A leads to B ?
Could you please tell me, which one of your videos explains the idea of negating a complex idea? I am unable to figure out why does the complex idea need not be taken as is. Thank you. Very well explained by the way......
Hey Parth. I don't really understand your question.
What is a "complex idea"? A conditional statement with an AND or an OR?
To negate something is to contradict it.
But in conditional logic we also use a term called an "illegal negation". Those are different things.
Which one did you mean by "negating"?
And what does it mean to say "the complex idea is taken as is"?
If we had a conditional like, "If X, then Y and Z", negating that would be saying, "Nuh-uh. X doesn't guarantee Y and Z. It's possible for X to be true but Y or Z or both to be false."
If we have, "If X, then Y and Z"
then an illegal negation would be
"If not X, then not Y or not Z"
Not sure if that's an answer to your question, but feel free to clarify.
@@LSATLab you have answered my query perfectly... Thank you... Educating students on the internet for free is the most noble thing anyone can do.... I wish you all the best....
@24:06 why does it say at the bottom of the screen
" don't be fooled into thinking this way" =
/A -----> /B
B------->A
isn't that the contrapositive ? and therefore a logical way to think
We intended to suggest that those don't follow from the "Given" statement. So knowing that A ---> B, don't fall for thinking like ~A ---> ~B or B ---> A.
@@LSATLab okay I see
It was continuing from the top part ... understood
Thank you for the quick reply !!
amazing video!
This was so good!
Quick question - What to do when you see "Only When", for example - "Bank transactions are credited only when they occur before 3:00 pm" (LSAT 31, Logical Reasoning I, Q21), thanks!
The argument says that bank transactions are credited only when they occur before 3:00 pm. That’s a necessary condition. It didn’t say that they are always credited if made before 3:00pm. So it’s possible that this bank transaction actually wasn’t credited. (sufficient-necessary flaw)
How do I notice that this is a necessary condition, I thought its sufficient when I saw "When"
"if" = "when"
(both LEFT SIDE, sufficient indicators)
"only if" = "only when"
(both RIGHT SIDE, necessary indicators)
"if and only if"
"when and only when"
"then and only when"
(bi-conditional indicators ... very rare ... you don't need to symbolize these as conditionals if you don't want. They're just either/ors. Either both things are true or both things are false.)
@@LSATLab oh man, I got played by this in that question haha, thanks for clarifying!
im go glad i stumbled upon this video
@9:08 Only B's can be A. Why wouldn't that be translated to if B then A or B-->A?
“Only” is a word that introduces a necessary condition (i.e., the right side of the arrow).
wait I'm confused because you put "unless" on the right then for the practice problems you put it on the left?
There are a variety of ways to handle "unless", so I think you're just reacting to seeing different methods employed.
The most memorizable method (in my opinion) is "If-not"
X happens unless Y happens = ~Y --> X
Unless B is true, A is false = ~B --> ~A
Unless M is false, J is true = M --> J
Notice that the concepts attached to unless (Y, B, ~M) are all showing up on the left side, the trigger side, but they are all inverted from their original form.
Y became ~Y
B became ~B
~M became M
That's the idea of "if-not".
You put the inverted form of what's attached to the UNLESS on the left side of the arrow.
Another method discussed in the video is rephrasing an UNLESS statement as "one thing requires another".
You can't have X unless you have Y
means "X requires Y" = X --> Y
So when we were using that technique, you would have seen the idea attached to UNLESS (Y) show up on the right side of the arrow.
But notice, even with that method, we're still inverting the idea on the left side of the trigger.
The sentence said "can't have X" but our rule is saying "if X is true".
Amazing video thank u!
Question: At 9:23 , The statement says that "The only time A occurs is when B occurs". Here "the only" as well as "when" both are indicators for sufficient condition, then how do we decide which one to put left?
Good question; I'm surprised I used an example that tricky. "The Only" is the trump card. The "when" is really "only when", which shows the right side idea.
The test, only a couple times, has disconnected "only if" or "only when".
Meaning, instead of writing
"cows get cancer *only if* they eat fudge"
they write
"cows only get cancer if they eat fudge"
Those two sentences mean the same thing, but the second one scrambles our formulas, because we see both "only" and "if" as though they're separate triggers.
Saying "The only time A occurs is when B occurs" is somewhat similar. It means the same as "A occurs only when B occurs".
Ultimately, when we memorize a specific move for a specific word, we might be failing to consider possible exceptions in language that don't fit the formula. The formulas work 99% of the time but we want to be flexible and be willing to interpret an answer on the fly, using our comprehension of what the claim is saying to transform it into an if/then rule or an "X requires Y" type rule.
@@LSATLab Glad that you replied......thanks, it cleared the doubt.
Just to confirm I have understood it properly, i have another statement. If you don't mind please check, if the diagram is proper.
"The only people not interested in making money in the business world are people who are interested in improving their intellect."
Not interested in making money--->Improving intellect.
@@yashraj8827 That's correct (and definitely the less-confusing style of "the only" I should have used in that lesson, haha)
Great content
Please help resolve this issue so my husband and I stop arguing about it 😅!! In studying for the LSAT, I’m confused about the “only if” phrase. Another video explained it this way, and I’m wondering if they made a mistake. The sentence (perhaps an LG rule) says: “Rakesh is 5th only if Eustice is 1st.” Then it was diagrammed like this: R5 -->E1. The tutor explains that “if” is not the same as “only if”, so you cannot read it as “if Eustace is first, then Rakesh is fifth. My husband insists that you can, that they are the same. I explained the arrow; that you can’t go backwards, but now I’m confused. Is this a biconditional statement? If I were doing a logic game and this was one of the rules, I would certainly put Rakesh in 5th place if Eustace was in 1st. Why is that wrong??? The tutor says if Eustace is first, that tells us nothing about Rakesh. What am I missing?
Sorry for the delay, we're still playing catch up after the Thanksgiving break.
And sorry to your husband who appears to be wrong in this case.
Ask him if these two sentences mean the same thing:
"You're a tough man if you play in the NFL"
vs.
"You're a tough man only if you play in the NFL"
The first statement is guaranteeing us that all NFL players are tough men.
The second statement is saying that no one outside the NFL is a tough man.
In terms of memorizing these keywords, "if / when / all / any / each / every / *the only*" always indicate the idea that goes on the left of the arrow.
"only / only if / must / requires / always / guarantees / ensures / implies" always indicate the idea that goes on the right of the arrow.
Thanks for your reply. The list of keywords is helpful. And I’m no longer asking my husband for help in understanding conditional logic. 😅That’s ok, he knows lots of other things
@@LSATLab but if Rakesh is 5th it is certain E is 1st. Rakesh can only be 5th if E is 1st meaning if we put rakesh on 3rd we know E is not 1st.
@@aastha4641 If we put R on 3rd we have no idea where E is. E could be 1st, 2nd, whatever (just not 3rd, unless R is allowed to share that spot).
The rule says
R5 --> E1
If you're in a scenario where R is 3rd, then the rule has no applicability / no relevance / no power / no instruction we must follow.
It's a conditional rule,
"IF R is 5th, then you must do something".
But in any scenario where R is something other than 5th, the rule doesn't tell us anything.
Pretend you were reading a law that says,
"If your home is a daycare center, then you must do X."
Your home isn't a daycare center. Does this rule tell you anything that you must do?
Of course not. It's only a rule for homes that are daycare centers, just as "R5 --> E1" is only a rule for scenarios in which R is 5.
So for example #7, are you saying that that is technically one of the "bi-conditionals"? Are you effectively saying that:
If True Worshipper, then Accepted
AND
If Accepted, then True Worshipper
I am bit confused on what exactly the correct answer is there...
Yeah, that is a confusing example. No, not a bi-conditional, just two different acceptable conditionals.
What I was going for was the "any", which gives us
"if true worshipper, then that church will accept you"
But then I was acknowledging that people might have validly written
"If that church, then will accept any true worshipper".
That's not a bi-conditional because the ideas on the left and right are different.
We CANNOT for example say
"If that church accepts you, then you're a true worshipper"
We know they accept all true worshippers but they might also accept other type of people as well.
So the intended "correct answer" was
"If True Worshipper, then Accepted by that church"
But if you wrote
"If that church, then will accept any true worshipper", that is also a true rule.
I'm confused about the "unless love or passion" example, it looks like at the truth values are flipped twice at 15:44. From "or" initially, flipped to "and", and then back again to "or". I would have thought it is H -> L and P based on the initial statement.
- H not achieved unless L or P
- If H then L and P
I understand logically how it is "or" at the end, but based on the flipping truth values (a tip I found very helpful until this example), shouldn't it be "and"?
I must be overthinking this!
Otherwise finding your videos very helpful, thank you!!
~(L or P) = ~L and ~P
It's like distributing a negative through a parentheses in math.
It's also the same as what we do when we do contrapositives.
This sentence says, "Happiness requires love or passion", which would look like this
H --> L or P
The contrapositive involves flipping the truth values of everything, and flipping the left and right sides:
~L and ~P --> ~H
Suppose we said "if it's not the case that mom or dad is present, you can't use the stove".
Would you write
~M and ~D --> ~Stove
or
~M or ~D --> ~Stove
the first one is correct. We're saying that "when both mom and dad are absent, you can't use the stove".
the second one makes it look like you need both parents there to use the stove.
When you're working with UNLESS, you'll either change the first half of the statement or the second half, but never both. The half you change is the one that goes on the left of the arrow.
You said
"I would have thought it is H -> L and P based on the initial statement.
- H not achieved unless L or P"
That rule says "H is not achieved" and "L or P".
You only get to flip one of them, not both. You can flip either one, and put that on the left side, and then the other idea remains on the right.
I can flip "H is not achieved" and get
"If H is achieved, then L or P"
Or I can flip "L or P" and get
"if L isn't and P isn't, then H is not achieved"
Let me know if any of that is confusing.
@@LSATLab You're right, I was flipping both! Oops! Thank you!
Thank you
Very helpful..❤️
Here’s an exam of a LSAT Necessary Assumption QN, this is from Preptest 73, Section 2 QN 20.
Correct Answer Choice is E.
E) many, if not all, farmers in the region will not grow green-manure crops unless they abandon the use of chemical fertilizers.
I usually negate the answer to see if it destroys the argument as that’ll be the correct answer to the NA question, how to negate this one?
I initially did this - “Many farmers in the region will grow green-manure crops if they abandon the use of chemical fertilizer”
Online I found the correct negation would be - “Many farmers in the region will grow green-manure crops even if they do not abandon the use of chemical fertilizer”
I used “unless = if not” and then took the not away for negation
What did I miss?
Thanks!
I use the negation test too on NA but not for conditional logic answers. It's better to just ask ourselves whether the author made that move (we usually have to contrapose the answer, if it's correct, to see how it matches a move the author made).
When you negate a conditional idea, you don't get a conditional. You're saying, "Nuh-uh ... that certain connection from Left to Right doesn't exist."
If person 1 says, "All boys like football"
(Boy-->Likes Football) and Person 2 says, "Nuh-uh", that second person is only saying "there's at least one person who doesn't like football".
Negating/refuting/contradicting a conditional always means "it's possible that the Trigger happens but the Outcome doesn't".
If we're negating this,
"If they continue to use chemical fertilizers, then many, if not all, farmers in the area will not grow green manure crops", then we get "it's possible that they continue to use fertilizers, but almost no farmers will not grow green manure".
That's a double negative at the end, which is saying "almost all farmers will grow green manure".
Overall, to negate this answer you have to be able to do three tricky things:
1. understand that negating "A --> B" means "it's possible A is true and B isn't"
2. know that negating "many A's are B" gives us "almost no A's are B". (many doesn't have an exact minimum, but 'at least 5' is a good definition to work with, so when we negate that idea we're getting '0 - 4')
3. knowing to turn a double negative into a positive "no farmers will not grow green manure = all farmers will grow green manure"
That's brutal. It's easier to just ask ourselves, "Was our author thinking that if they don't stop using fertilizers, they won't start growing green manure?"
Another question. You said at the beginning, “The arrow is certainty….if the right side is true, it must be that the left side is true.” So what do we do with a sentence like this? “If you feed your rabbit, then you can go to the park.” Or “If you eat your vegetables, then you can have dessert.” If the left side happens, you feed the rabbit, or you ate your vegetables, that doesn’t necessitate that I did indeed go to the park or that I did indeed have dessert. Maybe I didn’t do either of those, so how can your statement be correct that it (the right side) MUST be true? Yes, it’s true that I “can” go to the park, but that doesn’t mean that I did. Can you please help me understand this?
Your first statement is hopefully a typo, because I hope I didn't say something wrong like "If the right side is true, it must be that the left side is true". That would be an illegal reversal.
The rest of your comment made it seem like you had the correct understanding, that the left side guarantees the right side (but not vice versa).
I think you're maybe just getting confused by using examples where the right side is saying that something is "possible".
When you say,
"If you feed rabbit, then you can go to park"
Then if we know that you fed the rabbit, we only know that "you CAN go to the park".
In the second example we would only know that "you CAN have dessert".
After all, that's what the right side said:
*Feed rabbit --> can go to park*
The left side tells us for sure that the right side is true. So if you fed the rabbit, we know for sure that you CAN go to the park.
Someone might write the same conditional in shorthand, as
*Feed Rabbit --> go to park*
If you write it that way, it might look like the right side is guaranteeing that you ACTUALLY went to the park, which is the misleading idea you're asking about. But that's not an issue with the concept that the left side guarantees the right side.
That's just an issue with the fact that when we abbreviate a rule so that we can write it on our page with an arrow, we might lose some of the nuance (i.e. writing 'go to park' doesn't allow our brain to see whether the idea was "CAN go to park" vs. "ACTUALLY went to park").
You just have to be mindful of the actual wording of the rule, not the shorthand abbreviation you wrote down.
Thank you for your response! Yes, that makes sense. I will pay attention to the wording.
Why is it that “only” introduces a necessary, but “the only” introduces a sufficient? This trips me up when practicing
It's just a weird tic of grammar. One thing you can do is just think, "Any time a sentence seems to be describing a requirement, I'll just think about the meaning and rephrase it as X requires Y", which is always diagrammed as X --> Y
All of these sentences mean the same thing:
- the only ppl who can practice law are those who pass the par
- you can practice law only if you pass the bar
- only people who pass the bar can practice law
And ultimately they all just mean
"Practicing law REQUIRES passing the bar"
So they'd all be diagrammed
*Practice Law --> Pass Bar*
@@LSATLab ahh that clarifies, I’ll have to be more conscious of it going forward. Thanks for the reply!
this is also true for analytical reasoning isn't it?
Correct, conditional logic is the same no matter where you encounter it.
OK, so I am a little bit confused for number eight. If the contrapositive is, you're not a cool person, and you don't use breath strips. Wouldn't be you're not a cool person and you used mints?
We know that uncool people "don't use breath strips instead of mints". Using breath strips instead of mints means that you DO use breath strips but DON'T use mints. So someone who doesn't fit that profile could be any of these:
- they use breath strips in addition to mints
- they doesn't use breath strips or mints
- they just use mints
Honestly, it was just a silly example that was meant to be "Only cool people use breath strips". I just didn't know if enough of the audience would even remember that ill-fated breath freshening technology from the late 90's early 00's, so I threw in "instead of mints" to clarify.
If we wanted to make this silly example more complicated, then technically the original rule is
BS and ~M --> Cool
so the contrapositive would be
~Cool --> ~BS or M
And that outcome would mean at least one of these is true:
- don't use breath strips
- do use mints
Thank you for explaining!
You are missing the equivalence of the negation of a conditional statement: ~(A=>B) =A and ~B
True story. Thanks for the suggestion. We're also missing a discussion of "nested conditionals", such as "If X, then Y, unless Z". But those are the editorial decisions you have to make when you're constrained by trying to keep it to our typical ~25 min length and trying not to overwhelm students who are new to conditional logic with the more advanced / esoteric applications of it.
I think we'll do an entire lesson video at some point on "Refuting a Conditional", because students often struggle when the conclusion is rebutting someone else's conditional claim.
Can some please help me understand X->Y is same as X requires Y my brain is going crazy . I always thought that its Y requires X. Pls in need of help
the left side is called the Sufficient condition.
the right side is called the Necessary condition.
If the right side is "necessary", then it's synonymous to say it's "essential / required / must follow".
If we say "passing the bar is required to practice law", that's synonymous with saying, "Passing the Bar" is a necessary thing, in order to Practice Law.
It's required. It must be done.
We can rephrase that as "Practicing Law passing the bar exam".
Should that look like
Practice Law --> Passed Bar
or
Passed Bar --> Practice Law
The 2nd one is tempting to people because they're thinking about the chronological order of events. First you pass the bar, then you practice law. Or they're looking at the arrow as though it's saying that "passing the bar" is your passport to "practicing law".
But the meaning of the conditional arrow isn't that it's showing us chronology or causality; rather, it's showing us certainty.
If I know you've passed the bar exam, am I certain that you practice law?
No. Tons of people might pass the bar but never get a job as a lawyer. Tons of people pass the bar, work as a lawyer, but then leave the field and no longer practice law.
Meanwhile, if I know you Practice Law, am I certain that you Passed the Bar?
Yes. Since passing the bar was a requirement to practice law, I know that if I see someone practicing law, then they passed the bar exam.
Thus, the correct way to symbolize it is
"Practice Law --> Passed Bar"
We can read that as
1. you practice law, I know you passed the bar
2. practicing law that you've passed the bar
3. people who practice law people who have passed the bar
The idea of Necessary / Required things is that if you meet a prerequisite, then you're screwed.
Not passed bar --> Can't practice law
That's the most intuitive way to think about necessary ideas. But when you contrapose that, you get
Can practice law --> passed bar
You do need to be careful about active voice vs. passive voice.
X requires Y = Y is required by X
If we write
Getting into Yale ---> 150+
We can read that as
"Getting into Yale scoring at least 150" or
"Scoring at least 150 is required in order to get into Yale"
@LSATLab to questions I don't know anything about how will I make out the necessary out and the sufficient. Here intuition helps but I'm still kinda low on confidence on this. 😞
I would recommend memorizing that cheat sheet at the end of the video, explaining which words mean "put this on the left of the arrow", which mean "put this on the right of the arrow", and which mean "put the negated form of this on the left of the arrow" (i.e. If-Not).
In 95% or more of cases in which we see conditional logic, we don't have to use intuition. We can just memorize those indicator words and thereby always get it right!
There's not much content for LSAT that one can memorize, but this is the exception. Bust out those flashcards. Make those words totally automatic. You should be able to rattle off from memory at least 6 words that indicate LEFT, 6 words that indicate RIGHT, and two words that indicate IF-NOT.
@@igneelfiredrag9274
@@LSATLab 🔥🔥♥️♥️♥️
@LSATLab what if there is like a negated(doesnot) statement on one or both sides in the required condition, then would the rule be not x -> not y.pls explain with an example it's superhelful you guys.