Am taking a Computer Science course, and your explanation was much better than anything I've seen - you aren't just helping future LSAT test takers. Thank you.
For UNLESS, you can take either part (A or F), negate it and make it the sufficient condition; the other part remains the same and becomes the necessary condition. E.g. /A -> F OR /F -> A
Yes, there would he 2 scenarios, 1) Abigail and Frank BOTH attend, or 2) NEITHER Abigail NOR Frank attend. “Terms in a double arrow relationship (if and only if) either occur together or both do NOT occur”
I dont get the Unless part, it is understandable up until 'If Frank doesnt go then Abigail will' and then it is also understandable that you flipped and negated. But in reality, we can not say anything about what Frank will do or not do can we? I truly cannot grasp the contrapositive of that. And though i can make it work in the test, i wanna know the mechanics behind it. How can we assume anything about what Frank will or will not do? Abigails going is dependent on his not going but only in the circumstance where frank goes or doesnt go. What i mean to say is that If Abigail does not go, then we can not say anything about what Frank will do.
"A unless F" means that the default state of events is Abigail going to the party. There is only one circumstance in which Abigail may not go to the party, and that circumstance is if Frank goes to the party. Thus, as long as Frank is not going, then we know for sure that Abigail is going to the party. Put differently, "A unless F" really means "The only way Abigail might not go is if Frank goes." As for the contrapositive, Abigail is going for sure if Frank does not. Thus, if Abigail is not going, then we can conclude that Frank must have gone.
In case of: V cannot unless both H and M go Going by what is explained above, it means if not H and M then V cannot. The contrapositive of this is: If V then H or M. But in the solution it is, if V then both H and M. How do we do this then?
Let's take it step by step. And for convenience, I'll use ~ to mean "not." The statement is: "V cannot go unless both H and M go." The "unless" portion of this statement is "unless both H and M go." The other portion is "V cannot go." The V portion is simple. This is just ~V and will go on the right side of the arrow. But what about the unless portion? We need to negate the phrase "both H and M go" and put it on the left side of the conditional. The key word here is "both." To negate this, we need something that means "not both." In other words, if we negate, then H going alone is fine and M going alone is fine. BUT H and M BOTH going is not allowed! Thus, this portion of the conditional statement reads "~(H and M)." Putting this all together, we get the following conditional statement: ~(H and M) -> ~V The contrapositive of this is: V -> (H and M) Does this make sense?
To answer the question, I'll use the following example: "A goes to the party only if B does not." Here, the conditional statement is A -> NOT B. In other words, If A goes to the party, then B does not. The contrapositive is B -> NOT A.
poor boy - I feel your pain. I've been messing around with this very idea for the last few days. I assume that you are talking about the unless part of the video. That is "A is going UNLESS F is going" this does indeed convert to "IF F is not going THEN A is going" the contrapositive is "IF A is not going THEN F is going." The bottom line of this is that somebody has to be at the party. What flies in the face of everyday usage of the unless statement is that it is also possible for both A and F to be at the party.
@@brucejones9628 Yeah I think I started to understand when I accepted that if A goes it has no impact on whether or not F goes. It still doesn't answer why if F goes A can go but whatever, I just accepted it.
Basically read it this way: Abigail definitely goes to the party if Frank doesn’t go. But if Frank does go, then she can decide to go or not go. /F -> A When Frank goes (meaning/F doesn’t happen) , Abigail is freed from this rule (meaning the above rule falls apart/disappears, making A a floater, or free to be A or /A). Hope this helps. :)
You will be homeless (A) unless you get a job (B). /B ---> A (If you did not get a job, then you are homeless). /A ---> B (If you're not homeless, then you did get a job). However... B ---> A (possibly true: You got a job, but are still homeless for whatever reason)
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Hey I just want to thank you for this explanation. It's been 6 years, with your clear thought, you must have been a good lawyer!
Ive watched so many videos on this topic and yours was the one that made it click for me. Thank you!
Am taking a Computer Science course, and your explanation was much better than anything I've seen - you aren't just helping future LSAT test takers. Thank you.
I absolutely agree! Same thing for me. I would describe as a "clean and straight" approach.
Man I gotta thank you, I’ve had problems with diagramming Only If and didn’t get it till now
For UNLESS, you can take either part (A or F), negate it and make it the sufficient condition; the other part remains the same and becomes the necessary condition.
E.g. /A -> F OR /F -> A
very good presentation thanks
Love the breakdown, will be reviewing this again, thank you!
For an if an only if statement are there 2 contrapositives, one for each statement?
Yes, there would he 2 scenarios, 1) Abigail and Frank BOTH attend, or 2) NEITHER Abigail NOR Frank attend.
“Terms in a double arrow relationship (if and only if) either occur together or both do NOT occur”
Thank you for the video! It's very helpful
Very helpful video. Thank you!
this was so helpful, thank you!
Thank you! This is very helpful!
thanks,,,could maybe also benefit further from an elaborated explanation of the "unless" contrapositive
I dont get the Unless part, it is understandable up until 'If Frank doesnt go then Abigail will' and then it is also understandable that you flipped and negated. But in reality, we can not say anything about what Frank will do or not do can we? I truly cannot grasp the contrapositive of that. And though i can make it work in the test, i wanna know the mechanics behind it. How can we assume anything about what Frank will or will not do? Abigails going is dependent on his not going but only in the circumstance where frank goes or doesnt go. What i mean to say is that If Abigail does not go, then we can not say anything about what Frank will do.
"A unless F" means that the default state of events is Abigail going to the party. There is only one circumstance in which Abigail may not go to the party, and that circumstance is if Frank goes to the party. Thus, as long as Frank is not going, then we know for sure that Abigail is going to the party. Put differently, "A unless F" really means "The only way Abigail might not go is if Frank goes."
As for the contrapositive, Abigail is going for sure if Frank does not. Thus, if Abigail is not going, then we can conclude that Frank must have gone.
In case of:
V cannot unless both H and M go
Going by what is explained above, it means if not H and M then V cannot. The contrapositive of this is: If V then H or M.
But in the solution it is, if V then both H and M.
How do we do this then?
Let's take it step by step. And for convenience, I'll use ~ to mean "not."
The statement is: "V cannot go unless both H and M go."
The "unless" portion of this statement is "unless both H and M go." The other portion is "V cannot go."
The V portion is simple. This is just ~V and will go on the right side of the arrow.
But what about the unless portion? We need to negate the phrase "both H and M go" and put it on the left side of the conditional. The key word here is "both." To negate this, we need something that means "not both." In other words, if we negate, then H going alone is fine and M going alone is fine. BUT H and M BOTH going is not allowed! Thus, this portion of the conditional statement reads "~(H and M)."
Putting this all together, we get the following conditional statement:
~(H and M) -> ~V
The contrapositive of this is:
V -> (H and M)
Does this make sense?
Thank you so much for your help! It was very helpful.
If in the question 'only if not' is there than what will be the answer
To answer the question, I'll use the following example:
"A goes to the party only if B does not."
Here, the conditional statement is A -> NOT B. In other words, If A goes to the party, then B does not.
The contrapositive is B -> NOT A.
Nailed it
I dont get it. If A goes is that not enough to know F isn't going? And if F is going does that not mean A isn't going?
poor boy - I feel your pain. I've been messing around with this very idea for the last few days. I assume that you are talking about the unless part of the video. That is "A is going UNLESS F is going" this does indeed convert to "IF F is not going THEN A is going" the contrapositive is "IF A is not going THEN F is going." The bottom line of this is that somebody has to be at the party. What flies in the face of everyday usage of the unless statement is that it is also possible for both A and F to be at the party.
@@brucejones9628 Yeah I think I started to understand when I accepted that if A goes it has no impact on whether or not F goes. It still doesn't answer why if F goes A can go but whatever, I just accepted it.
Basically read it this way:
Abigail definitely goes to the party if Frank doesn’t go. But if Frank does go, then she can decide to go or not go.
/F -> A
When Frank goes (meaning/F doesn’t happen) , Abigail is freed from this rule (meaning the above rule falls apart/disappears, making A a floater, or free to be A or /A). Hope this helps. :)
You will be homeless (A) unless you get a job (B).
/B ---> A (If you did not get a job, then you are homeless).
/A ---> B (If you're not homeless, then you did get a job).
However...
B ---> A (possibly true: You got a job, but are still homeless for whatever reason)
How about "I will go hiking unless it is winter"
Of all the wording the only one im not okay with is unelss, its just too far from the normal meaning of unless
thanks so much
if you watch this video then you will get an A in discrete math
The mouse movement made me nauseous...