Can someone explain the Maria training hard one better because I thought it’s all supposed to move in the same direction. Answers B I thought incorrectly flips the sufficient and necessary conditions
@AlenaKane How I got it to sort of click, if you flip them it is still 'true' if you negate both sides. If you're visual, pause the video around 14:10, that graphic helped me a lot.
To go back to the Texas example: If you are in Texas you are in the US. But if you flip the two AND you also 'negate' them it is still true: If you are not in the US, you are not in Texas.
@annalior02 Let's look at the initially expressed conditional relationship.
"If an action is performed out of self-interest, then it should not be considered generous."
or, condensed for smoother reading,
"in self-interest -> not considered generous."
Remember, a contrapositive not only reverses the component statements, but also the order of the statements. The contrapositive of this conditional relationship is:
"considered generous -> not in self-interest" or "If an action should be considered generous, then it was not performed out of self-interest."
What can we conclude from that contrapositive? Given the knowledge that some action should be considered generous, then we know for sure that it was not performed in self-interest. However, the relationship in the third and fourth sentences looks different. Stated in the terms of the initial conditional, it reads "not in self-interest -> considered generous." This error is an example of inverting the conditional, or confusing a sufficient condition with a necessary condition.
Returning to the first example given in the video, "If a person is in Texas, then they must be in the United States," the logic structure applied in the passage would conclude that "If a person is NOT in Texas, then they must NOT be in the United States." Nebraskans would have a bone to pick with that logic, and for good cause.
Maybe it’s just me, but a lot of this video felt pretty intuitive to understand and the material felt pretty easy. I think what confused me more were classifications like “necessary sufficient” or “contra positive.”
I still cannot understand sufficient and necessary ;-; doesn't make sense, guess I'll have to try and learn that but it feels like I'm missing something
This is very helpful because for me the hardest questions I had on the LSAT were the ones asking me if the argument is invalid because they’re mixing necessary with assumption or vice versa. I’ve heard of the premise of these questions but at the time I had no clue which was which!
Regarding the point at 15:15, would it be valid to say that the business owner may have donated $1B to avoid paying taxes to a government she despises?
@Nick.Azar 100% but thé LSAT doesn’t care about real possibilities it only cares about the actual logic. When you take the exam youll see they ask you questions about niche topics to try to throw you off, making you think you need background information when in reality all you need is the logical reasoning behind the question and answer!
Would it be fair to take "unless/only if" as absolutes which, if not taken with other conditions we can safely assume are true? That's what I gleaned from the ice question, at least
"If the necessary condition is not true, then we must conclude that the sufficient condition is also not true" sounds like something worth remembering?
I didn't like how in the video it mentioned useing the contrapositive to help describe an argument but then in the very first practice question, it provided a direct example of how using the contrapositive STILL doesn't help you make sense of the argument
@wgresh No that is LITERALLYYYYY what I am saying. He said it group three, you can think of unless as introducing a necessary condition, but uses it in the sufficient sense. That just messed my understanding up. Can anyone help! :-(
@wgresh Are you referring to the argument about self-interest? Are you able to describe more specifically what you're confused about?
The question fundamentally is about this:
"If A, then Not B"
does NOT prove
"If Not A, then B"
If you're thinking, "but what about the contrapositive?" The contrapositive of the original statement "If A, then Not B" is "If B, then Not A." That's not the same thing as "If Not A, then B."
Consider coming up with different examples using more real-life concepts. For example:
If something is a fish, then it's not a mammal.
Does that prove that if something is NOT a fish, then it IS a mammal?
For Part 2, recognizing conditionals, I'm having a really hard time understanding Groups 3 and 4. Group 1 and 2 make sense but I cant seem to grasp the others.
That means "Not B" is sufficient for "Not A." And "Not A" is necessary for "Not B."
Does that make sense?
So a contrapositive doesn't change the relationship between A and B. A is still suffiicent for B. It's just that you can say "Not B" is sufficient for "Not A."
128 comments
Can someone explain the Maria training hard one better because I thought it’s all supposed to move in the same direction. Answers B I thought incorrectly flips the sufficient and necessary conditions
@AlenaKane How I got it to sort of click, if you flip them it is still 'true' if you negate both sides. If you're visual, pause the video around 14:10, that graphic helped me a lot.
To go back to the Texas example: If you are in Texas you are in the US. But if you flip the two AND you also 'negate' them it is still true: If you are not in the US, you are not in Texas.
@nick.treb thank you! Drawing it out did help
im cooked
@AlaniKirkland give it some time, it will click
Anyone else reading Loophole and is now even more confused after watching this video?
How is the first quiz not an example of triggering the contrapositive? I'm lost...
@annalior02 Let's look at the initially expressed conditional relationship.
"If an action is performed out of self-interest, then it should not be considered generous."
or, condensed for smoother reading,
"in self-interest -> not considered generous."
Remember, a contrapositive not only reverses the component statements, but also the order of the statements. The contrapositive of this conditional relationship is:
"considered generous -> not in self-interest" or "If an action should be considered generous, then it was not performed out of self-interest."
What can we conclude from that contrapositive? Given the knowledge that some action should be considered generous, then we know for sure that it was not performed in self-interest. However, the relationship in the third and fourth sentences looks different. Stated in the terms of the initial conditional, it reads "not in self-interest -> considered generous." This error is an example of inverting the conditional, or confusing a sufficient condition with a necessary condition.
Returning to the first example given in the video, "If a person is in Texas, then they must be in the United States," the logic structure applied in the passage would conclude that "If a person is NOT in Texas, then they must NOT be in the United States." Nebraskans would have a bone to pick with that logic, and for good cause.
Maybe it’s just me, but a lot of this video felt pretty intuitive to understand and the material felt pretty easy. I think what confused me more were classifications like “necessary sufficient” or “contra positive.”
One year later, and it finally clicked. WOW
I still cannot understand sufficient and necessary ;-; doesn't make sense, guess I'll have to try and learn that but it feels like I'm missing something
This is very helpful because for me the hardest questions I had on the LSAT were the ones asking me if the argument is invalid because they’re mixing necessary with assumption or vice versa. I’ve heard of the premise of these questions but at the time I had no clue which was which!
Shucks
my brain is pulsing
Regarding the point at 15:15, would it be valid to say that the business owner may have donated $1B to avoid paying taxes to a government she despises?
@Nick.Azar As humans I feel like everything we do is either generous or selfish in some way
@Nick.Azar 100% but thé LSAT doesn’t care about real possibilities it only cares about the actual logic. When you take the exam youll see they ask you questions about niche topics to try to throw you off, making you think you need background information when in reality all you need is the logical reasoning behind the question and answer!
Okay this makes sense, the only thing super tricky for me is unless!!
?
Defeated on Quizzes
im even more confused
@anna23 The rest of the module breaks things down in more detail and piece by piece, so I encourage you to work through the whole module.
dangerous sidewalks -> not open to public
icy sidewalk -> dangerous
if icy sidewalk -> not open to public
CONTRAPOSITIVE: if open to public -> not icy sidewalk
therefore valid conclusion.
"If the first part begins with no, than the second part is not true" is something I also feel is important idk lol
Would it be fair to take "unless/only if" as absolutes which, if not taken with other conditions we can safely assume are true? That's what I gleaned from the ice question, at least
"If the necessary condition is not true, then we must conclude that the sufficient condition is also not true" sounds like something worth remembering?
somehow I understand part 2 much more than part 1. Why do I understand the more complex argument more? SO frustrating.
pain
I didn't like how in the video it mentioned useing the contrapositive to help describe an argument but then in the very first practice question, it provided a direct example of how using the contrapositive STILL doesn't help you make sense of the argument
@wgresh No that is LITERALLYYYYY what I am saying. He said it group three, you can think of unless as introducing a necessary condition, but uses it in the sufficient sense. That just messed my understanding up. Can anyone help! :-(
@wgresh Are you referring to the argument about self-interest? Are you able to describe more specifically what you're confused about?
The question fundamentally is about this:
"If A, then Not B"
does NOT prove
"If Not A, then B"
If you're thinking, "but what about the contrapositive?" The contrapositive of the original statement "If A, then Not B" is "If B, then Not A." That's not the same thing as "If Not A, then B."
Consider coming up with different examples using more real-life concepts. For example:
If something is a fish, then it's not a mammal.
Does that prove that if something is NOT a fish, then it IS a mammal?
For Part 2, recognizing conditionals, I'm having a really hard time understanding Groups 3 and 4. Group 1 and 2 make sense but I cant seem to grasp the others.
If an original argument has a necessary and sufficient condition, does changing it to the contrapositive flip which condition is which?
@AnnaliseRamirez If A, then B.
A is sufficient for B. B is necessary for A.
The contrapositive is If Not B, then Not A.
That means "Not B" is sufficient for "Not A." And "Not A" is necessary for "Not B."
Does that make sense?
So a contrapositive doesn't change the relationship between A and B. A is still suffiicent for B. It's just that you can say "Not B" is sufficient for "Not A."
@Kevin_Lin yes it does, thanks so much!
Needed this to refresh
Am I the only one that is still so confused about all of this
@KatherineMarroquin same here
@KatherineMarroquin The rest of this module explores these concepts in a lot more detail. I encourage you to work through rest.