Negating the Conditional Idea to Existential Idea

DByrne07

Hello all, I was wondering what type of questions we’ll see that require us to pick an answer choice where we are negating the conditional idea or where negating a conditional idea (vice versa with existential) is blended with the existential idea? Weakening maybe? How does negating a conditional idea tie into the type of question we’d expect to see on the LSAT? Does that make sense or am I’m confusing myself? 7SAGE did a great job explaining how negating existential / conditional ideas was accomplished, but having trouble understanding where either apply in Logical Reasoning. Thanks!

Cant Get Right

That is an excellent, and very big question.

So what you will not see is a correct answer choice that just straight up negates a statement from the stimulus. When JY says not to attack the premise on a Weaken question, this is exactly what that means. Of course, denying a Necessary assumption absolutely devastates an argument. And that’s exactly why they aren’t going to give you an option to negate a stated Necessary Assumption. That would be the equivalent of giving you “Nuh Uh,” as an answer choice.

That being said, understanding negation is a really essential concept throughout LR. I think one of the most conspicuous examples is in the use of contrapositives. So A -> B, for example, you’ve also got B -> A. These are equivalent statements, and you understand negation -> you understand contrapositives.

So, say you’re being asked for the principle that allows the conclusion to be properly drawn. You map out your premises and it looks something like this:

A -> B
A
therefore C

So what you’re really looking for is B -> C. They wouldn’t be so kind as to give you A -> C. So, if they give you an answer that reads "if B then C” then that’s great. But if they give you "if not C then not B," that’s equally great; but the only way you know that is if you understand how the negation plays into it.

I can’t think of a question type off the top of my head where they couldn’t work in negation. I guess main point or something like that, but anything concerning conditional reasoning is in play.

The other major issue with negation is that if you’re not fluent with it, you won’t be able to translate anything into logic to begin with. You can know that “unless" means to "negate sufficient" all day long, but if you don’t know what that means, it doesn’t help you.

I hope this answers your question! Whatever your understanding of how exactly it plays into LR, just know that it’s something you’ve got to really master.

Skywalker

@"Cant Get Right"

Great explanation. One question:

Could you expound on what you mean in the latter part of: " You can know that “unless" means to "negate sufficient" all day long, but if you don’t know what that means, it doesn’t help you.

Cant Get Right

Oh yeah, sorry, that was really poorly worded. Basically all I meant was, if you don’t know what negation is, you can’t know what negating the sufficient is.

On a deeper level though, it’s also important to understand negation conceptually. So, I think one of JY’s examples is, “What is the negation of hot?” A lot of people will say “cold,” and it’s important to know why that’s wrong. Even if you can translate things into our logical language, if your underlying understanding of that is mistaken, that presents a really big problem.