Advanced LSAT Negation Techniques: Part I of III
You’re several minutes into the logical reasoning section and on question five. It’s a necessary assumption question. Great! You know how to do those. You read the argument and boil the core down to:
Premise: Richie hates snails.
Conclusion: Richie will stomp on that snail over there.
You are relieved to spot the assumption immediately: If Richie hates something, he will stomp on it.
Reading through the answer choices, you look for one that matches. You get rid of C, D, and E easily. A and B remain, and they both look pretty good because they’re both about stomping and hating snails. Luckily, you know what to do at this point: Negate each answer to see what happens. If negating (making it untrue) wrecks the argument, that means it’s necessary, i.e. your answer!
But wait. B reads, “If Richie hates something, sometimes he kills it.”
You’re at a loss on how to negate that. Do you say, if Richie doesn’t kill something, he doesn’t hate it? Or if he doesn’t hate it, he’ll kill it? Or if he does hate it, he won’t kill it? How do you negate an “if” statement?
To negate a conditional, negate the necessary clause. Leave the conditional clause (the “if” clause) alone. In this case the correct negation would be the third one above: If Richie hates something, he won’t sometimes kill it (or he’ll never kill it, same thing).
What happens to our argument when we put it that way? Destroyed! Answer choice B is correct.
Come back to the blog next week for Part II of Advanced Negation Techniques.