really like the part where they said "validity is (if(or pretend that)) all the premises are true". good way to remind yourself to remove bias and other logic and whatever you read is the truth and nothing else.
So, validity is a machine where 1 + 1 = 2, and truth is interrogating 1, 1, and 2 to see if they're actually 1, 1, and 2? Does that metaphor work for these purposes?
Like, validity is quantitative and truth is qualitative?
@CourteousWelcomingBathroom My take is if the premise read "the water is solid" then, solid will be the water for the exercise. No more reasoning added.
Is it true in real world? No. And that does not matter when it comes to resolve de question.
@CourteousWelcomingBathroom I usually think of this example
All pigs can fly.
Wilbur is a pig.
Therefore, Wilbur can fly.
This argument is valid because the conclusion follows logically from the premises. However, it is not sound (true) because the premise "All pigs can fly" is false.
@ogall I think for LR the assumption is always to focus on validity, but for RC you'll focus more on truth (since it is testing your ability to surmise the truth from the passage)
Aw man, I skipped these foundational lessons for the sake of time and I'm glad I'm reviewing them now. I would get questions wrong on a factual basis, and was really confused why the test wanted me to believe things that made no factual sense. Thank you, 7Sage!
Reposting my comment from before because I'm re-reviewing...
What helps me is to think of it like this:
A valid or invalid argument depends on the STRUCTURE of the argument! The truth of the claim does not matter. A valid argument can have false claims.
So: If A then B. X is A. Therefore, X is B. (Valid)
But: If A then B. X is C. Therefore, X is A. (invalid) -- this is invalid because we don't know the relationship between C and A.
If this same argument read like:
If A then B. If C then also A. X is C. Therefore, X is A. (it becomes valid)
because of the structure. I try to avoid the word "truth" all together:
If a person is a boy (if A), then the person is a bottle of lotion (then B). If one smells like vanilla (if C) then one is also a boy (then also A). Samantha smells like vanilla (X is a member of C), therefore Samantha is a boy. (X is A).
Technically, this is a valid argument...but far from the truth. But the structure allows for the conclusion to logically follow the premises.
You really have to train the brain to leave the real world at the door.
This part is so hard to accept because my brain immediately refuses to accept the argument based of the falsehoods it generated. The truth is all teenage mutant turtles are ninjas. But the LSAT is rage baiting by saying nah just turtles just to trick people judging the truth.
basically, pretend that the convo ur having w ur friend (the lsat question) is indeed true and ur just making sure that they didn't leave out or switch up any critical parts of the story (evaluating premise content and overall reasoning formula for conditional argument) ???
A valid or invalid argument depends on the STRUCTURE of the argument!
So: If A then B. X is A. Therefore, X is B. (Valid)
But: If A then B. X is C. Therefore, X is A. (invalid) -- this is invalid because we don't know the relationship between C and A.
If this same argument read like:
If A then B. If C then also A. X is C. Therefore, X is A. (it becomes valid)
because of the structure. I try to avoid the word "truth" all together:
If a person is a boy (if A), then the person is a bottle of lotion (then B). If one smells like vanilla (if C) then one is also a boy (then also A). Samantha smells like vanilla (X is a member of C), therefore Samantha is a boy. (X is A).
Technically, this is a valid argument...but far from the truth. But the structure allows for the conclusion to logically follow the premises.
@AidenG123 Sorry just seeing this, yes! There are many ways to make an argument valid.
Another thing that can help me is to write it out side by side. The boy is the sufficient condition/subset to Lotion (Necessary condition/Superset) in P1. Then in P2, the lotion is a sufficient condition/subset to Vanilla (Necessary condition/Superset). So, here you have lotion as both a superset and subset which is fine [see lesson on sets].
In some cases, it can be helpful to write the premises in one row:
For me, writing it side by side when it is simple like this, makes it easier to see that the conclusion is guaranteed. In your example we can literally see the conclusion.
Boy (A) --> Lotion (B) --> Vanilla (C) [see lesson on chaining arguments]
Validity does not equal to truth. However, if all premises are true then the conclusion must be true. This makes an argument valid. An invalid argument depends on the truth of the premises.
If you're struggling with the information clicking, I would recommend watching again. The biggest point of this is that the reasoning is the most important thing when trying to determine if something is valid. Wether it is true or false doesn't necessarily matter because we aren't looking at most arguments from a real world lense anyways.
The plans for a building cannot be "true" or "untrue." They can, however, be structurally sound (valid) or structurally unsound (invalid).
Now, I tell you I'm going to build a house in Wonderland. I show you the blueprint. It is mathematically and structurally perfect—i.e., valid. If Wonderland were real, it would work flawlessly. And that validity is totally irrelevant to the "truth" of my premises, being that Wonderland is a real place I can build a house in.
How I am understanding this is even though the premises can be false, as long as the premises match the conclusion, it is a valid argument. You aren’t looking if the actual claims are “true” or factually correct. You are looking at the form of the argument and if the premises support the conclusion. If it does, then it's a valid argument.
To tie it back to subsets/supersets: an argument is valid if the set of all universes where its premises are true is a subset of the set of all universes where its conclusion is true. So the premises' truth is sufficient for the conclusion's truth, and the conclusion's truth is necessary for the premises' truth.
What happens if we are asked to take a case on in the real world and there are false premises that support the validity of the argument you're trying to make. Should we lie to juries that we are giving them true premises when giving false ones while obscuring true premises that harm the validity of our argument? How do we decide if the ends justify the means? Doesn't that mean we have an interest in being dishonest to people? Surely most other people conflate truth with validity.
@mszchloechen640 I think that is a very reasonable ethics dilemma... but, in the case of the LSAT, I argue that we are not worried with ethics or what a jury would think if there is false/true premises.
so basically, your job isn't to decide whether the statements are true or false. Instead, you're focused on analyzing the structure of the argument to determine if it's logically valid.
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68 comments
really like the part where they said "validity is (if(or pretend that)) all the premises are true". good way to remind yourself to remove bias and other logic and whatever you read is the truth and nothing else.
So essentially the premises is not an assumption ever, it is the truth.
My favorite way someone told me to to remember this is "attack the argument, not the premises."
So, validity is a machine where 1 + 1 = 2, and truth is interrogating 1, 1, and 2 to see if they're actually 1, 1, and 2? Does that metaphor work for these purposes?
Like, validity is quantitative and truth is qualitative?
@CourteousWelcomingBathroom My take is if the premise read "the water is solid" then, solid will be the water for the exercise. No more reasoning added.
Is it true in real world? No. And that does not matter when it comes to resolve de question.
@CourteousWelcomingBathroom I usually think of this example
All pigs can fly.
Wilbur is a pig.
Therefore, Wilbur can fly.
This argument is valid because the conclusion follows logically from the premises. However, it is not sound (true) because the premise "All pigs can fly" is false.
From my understanding with the help of chat and broke it down for me easily!
Think of it like a pattern:
If A → B
X is A
→ therefore X is B ✅
This is valid because it follows the rule correctly.
🧩 Example (simple)
If it rains → ground is wet
It is raining
→ ground is wet ✅
This makes sense AND is logically valid.
🚫 Invalid example
If A → B
X is C
→ therefore X is A ❌
Why is this wrong?
Because:
👉 we don’t know how C relates to A
There’s no connection.
🔁 When it becomes valid
If A → B
If C → A
X is C
→ therefore X is A ✅
Now it works because:
C leads to A
X is C
so X must be A
How do you know when to base the answer to the question on validity or truth?
@ogall I think for LR the assumption is always to focus on validity, but for RC you'll focus more on truth (since it is testing your ability to surmise the truth from the passage)
Aw man, I skipped these foundational lessons for the sake of time and I'm glad I'm reviewing them now. I would get questions wrong on a factual basis, and was really confused why the test wanted me to believe things that made no factual sense. Thank you, 7Sage!
Reposting my comment from before because I'm re-reviewing...
What helps me is to think of it like this:
A valid or invalid argument depends on the STRUCTURE of the argument! The truth of the claim does not matter. A valid argument can have false claims.
So: If A then B. X is A. Therefore, X is B. (Valid)
But: If A then B. X is C. Therefore, X is A. (invalid) -- this is invalid because we don't know the relationship between C and A.
Technically, this is a valid argument...but far from the truth. But the structure allows for the conclusion to logically follow the premises.
You really have to train the brain to leave the real world at the door.
aaaaand there is my answer.
@JeremyM you got this!!!
This part is so hard to accept because my brain immediately refuses to accept the argument based of the falsehoods it generated. The truth is all teenage mutant turtles are ninjas. But the LSAT is rage baiting by saying nah just turtles just to trick people judging the truth.
basically, pretend that the convo ur having w ur friend (the lsat question) is indeed true and ur just making sure that they didn't leave out or switch up any critical parts of the story (evaluating premise content and overall reasoning formula for conditional argument) ???
Will Must Be True questions seek to conflate these within the answers provided to us?
What helps me is to think of it like this:
A valid or invalid argument depends on the STRUCTURE of the argument!
So: If A then B. X is A. Therefore, X is B. (Valid)
But: If A then B. X is C. Therefore, X is A. (invalid) -- this is invalid because we don't know the relationship between C and A.
Technically, this is a valid argument...but far from the truth. But the structure allows for the conclusion to logically follow the premises.
@16dnholli would the argument be made valid If it said all bottles f lotion smell like vanilla?
This would make the chain
P1:Boy (A) --> Lotion (B)
P2: Lotion (B) --> Vannilla (C)
C: A --> C?
@AidenG123 Sorry just seeing this, yes! There are many ways to make an argument valid.
Another thing that can help me is to write it out side by side. The boy is the sufficient condition/subset to Lotion (Necessary condition/Superset) in P1. Then in P2, the lotion is a sufficient condition/subset to Vanilla (Necessary condition/Superset). So, here you have lotion as both a superset and subset which is fine [see lesson on sets].
In some cases, it can be helpful to write the premises in one row:
P1:Boy (A) --> Lotion (B) ; P2: Lotion (B) --> Vanilla (C);
Therefore: Boy (A) --> Vanilla (C)
For me, writing it side by side when it is simple like this, makes it easier to see that the conclusion is guaranteed. In your example we can literally see the conclusion.
Boy (A) --> Lotion (B) --> Vanilla (C) [see lesson on chaining arguments]
Validity does not equal to truth. However, if all premises are true then the conclusion must be true. This makes an argument valid. An invalid argument depends on the truth of the premises.
so its still a good rule of thumb to not use your outside knowledge on the test?
@KeziaH19 yup
“I think we all know the definition of truth and yes, it’s what you think.”
… phew
thank you to freshman me for wanting to be a philosophy major instead of a polisci major
If you're struggling with the information clicking, I would recommend watching again. The biggest point of this is that the reasoning is the most important thing when trying to determine if something is valid. Wether it is true or false doesn't necessarily matter because we aren't looking at most arguments from a real world lense anyways.
The plans for a building cannot be "true" or "untrue." They can, however, be structurally sound (valid) or structurally unsound (invalid).
Now, I tell you I'm going to build a house in Wonderland. I show you the blueprint. It is mathematically and structurally perfect—i.e., valid. If Wonderland were real, it would work flawlessly. And that validity is totally irrelevant to the "truth" of my premises, being that Wonderland is a real place I can build a house in.
@AnnabelleNeidl Great way to put it
@AnnabelleNeidl
You probably just raised somebody's LSAT score like 5 points, by yourself, lol.
@AnnabelleNeidl Goated comment
How I am understanding this is even though the premises can be false, as long as the premises match the conclusion, it is a valid argument. You aren’t looking if the actual claims are “true” or factually correct. You are looking at the form of the argument and if the premises support the conclusion. If it does, then it's a valid argument.
Pls correct me if I am wrong.
Put differently, Validity means the premise logically supports the conclusion. (The math makes sense.)
To tie it back to subsets/supersets: an argument is valid if the set of all universes where its premises are true is a subset of the set of all universes where its conclusion is true. So the premises' truth is sufficient for the conclusion's truth, and the conclusion's truth is necessary for the premises' truth.
What happens if we are asked to take a case on in the real world and there are false premises that support the validity of the argument you're trying to make. Should we lie to juries that we are giving them true premises when giving false ones while obscuring true premises that harm the validity of our argument? How do we decide if the ends justify the means? Doesn't that mean we have an interest in being dishonest to people? Surely most other people conflate truth with validity.
@mszchloechen640 I think that is a very reasonable ethics dilemma... but, in the case of the LSAT, I argue that we are not worried with ethics or what a jury would think if there is false/true premises.
wouldn't that lead to advocating for a position based on false premises in the real world, leading to being unethical?
good question...
so basically, your job isn't to decide whether the statements are true or false. Instead, you're focused on analyzing the structure of the argument to determine if it's logically valid.