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?

I have in my notes written (A -> B) -> (A -> C) contrapositive = (A <-some-> /C) -> (A <-some-> /B) but I don't think that's right.

Shouldn't the contrapositive be (/C -> /A) -> (/B -> /A)? Is what I wrote in my notes maybe the negation of that embedded conditional that I was referring to?

Can anyone also point out where in the fundamentals this is referred to? Thank you!

Hello. I'm going over the core curriculum and JY tells us in order to negate "all" statements like "A -> B," you make it to "A <-some-> /B." However, in the next lesson, he tells us when you negate "conditional" statements like "A -> B," you negate it to "A and /B." My question is how do we differentiate between the two? Isn't an "all" statement the same as a "conditional" statement? If I say "all dogs are friendly," that is surely an "all" statement and diagramed as the conditional statement "dog -> friendly." Thus, I do not see the difference between the two.

I saw an explanation that said A -> B and A-some-> C = can conclude C -some-> B. Why is that and where can I find lessons on these types of conditionals?