Self-study
Hello. JY tells us in the core curriculum that the word "no" is a group 4 indicator where we choose a necessary and negate it. However, on LSAT 144 sec 2 question # 23 the statement is "no action based on good intentions are justified unless they also result in success" which the explanation translates it to "not successful -> not justified." However, by the group 4 logic indicator lesson's explanation it should be "not justified -> not successful" (I chose to negate "justified" by making it a sufficient and negating it due to the "unless" rule and chose "success" as the necessary and negated that due to the group 4 rule). So which one is it? Do different type's of "no's" have different logical indicators?
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However, by the group 4 logic indicator lesson's explanation it should be "not justified -> not successful" (I chose to negate "justified" by making it a sufficient and negating it due to the "unless" rule and chose "success" as the necessary and negated that due to the group 4 rule). The problem happened here. You are trying to apply unless and not at the same time and it's causing errors. You have to first apply one and see what remains and then do more.
So for the sentence: no action based on good intentions are justified unless they also result in success
let's start with "no". It's a group 4 indicator and it applies to the necessary part of the sentence. so let's translate it.
If an action based on good intentions are justified "not unless" they also result in success. Here the not is applied to the word unless because it's in the necessary part of the sentence. and "not not" "two negatives" make a positive. That's why it cancels each other out and you get : Justified -> success
Let's say i pick "unless" to apply first. Unless translates to "if not"
If "not no" action based on good intentions are justified they also result in success. Again, we get two negatives and they cancel each other out.
As a rule of thumb, that's why we say when you see group 4 and group 3 indicator, they are two "not's" and they just cancel each other out.
Hey, you are correct that "no" is a group 4 indicator and the correct translation of it is negating the necessary condition. However, in the example you gave "no action is based on good intentions are justified unless they also result in success" as you also mentioned contains group 3 negate sufficient indicator "unless". As a rule of thumb, where there are 2 negations, they just cancel each other out, therefore, you can just diagram the statement as justified -> successful which the contrapositive is going to be not successful -> not justified. Hope it makes sense!