@Natalie (A) is the reverse of the statement and you cannot just reverse a Sufficient & Necessary statement.
The contrapositive requires you to reverse AND negate.
Sufficient & Necessary is by far the most commonly tested form of reasoning on the LSAT, so you want to know these concepts like the back of your hand.
For a more detailed discussion of these concepts, make sure you check out our video lesson on Sufficient & Necessary conditions.
CMarrOctober 23, 2019
Why couldn't it be CO -> DV
If only chosen one can defeat Voldemort.... can't this also work
Just to make it clear ... when does one reverse the s
CMarrOctober 23, 2019
When does one reverse the statement vs. keeping the same structure as seen in the question ^
CelineJuly 15, 2020
I think this will create a direct causal relationship, if he is the one, then he must defeat V. But there is the chance that he is the one but he cannot defeat V. So it should be the other way around. I also did this question wrong, I chose A
CelineJuly 15, 2020
^ above is the reason for why not choose A
VictoriaJuly 16, 2020
Hello! Hopefully I can help clear things up a bit.
The reason that answer choice (A) is incorrect is because this is an "unless" statement.
There are two steps to diagramming "unless" statements:
(1) The part of the sentence which follows "unless" is the necessary condition. (2) Negate the other part of the sentence; this is the sufficient condition.
Necessary: Chosen One
Sufficient: Not Defeat Voldemort - but we have to negate this! Sufficient: Defeat Voldemort
DV --> CO Not CO --> Not DV
@CMarr, we could also rewrite this sentence to be an if/then statement; however it would read:
If Harry could defeat Voldemort, then he must be the chosen one.
DV --> CO
Answer choice (A) is incorrect because it is an improper reversal of the correct diagram.
Hope this is helpful! Please let us know if you have any further questions.
lesliebritneyJune 18, 2021
Hi! Do you always have to the negate the sufficient or only when you need it to match with the necessary's direction?
