How to Negate Conditional Statements when approaching Necessary Assumption Answer Choices?

pinklights98

Hi!

I am really struggling with how to negate conditional statements when they appear in the answer choices of necessary assumption questions.

For instance, a few that appeared in recent LSATs.

PT71 S1 Q22: Answer Choice E: Any pricing practice that does not result in unreasonable prices should be acceptable.

The Powerscore Logical Reasoning Bible says to add a "not" to negate, but I'm not sure where to add the not. Also, does any turn into some?

PT73 S4 Q26: Many farmers will not grow green manure unless they abandon the use of chemical fertilizers.

PT77 S4 Q26: (wrong answer choice): Sea Creatures have rarely if ever, wreaked ecological havoc in a new habitat unless they have been able to survive in that habitat after having been deposited by oceangoing ships.

Each time I struggle with such answer choices because I am unsure of how to negate them.

Thanks!

Admin Note:
https://7sage.com/lsat_explanations/lsat-71-section-1-question-22/
https://7sage.com/lsat_explanations/lsat-73-section-4-question-26/
https://7sage.com/lsat_explanations/lsat-77-section-4-question-26/

Sailor Moon LSAT

Remember that to negate a conditional statement, you would say "it is not the case before hand"; if you don't intuitively understand what that means, you basically take the first part, and negate the second part if you have logic.

If it's just a statement, you are doing NOT. I think the first one is just a statement, and not so much logic.

I hope these explanations help, and if I'm wrong on anything that anyone else notices, let me know!

For 71 S1 Q22, to negate this, you would put in a not, so it would be Any pricing practice that does not result in unreasonable prices should not be acceptable.
I think it could be confusing because you maybe would want to say any pricing practices that do result... but that does not negate it, because that "does not result" is just modifying what type of pricing practice.

For PT 73 S4 Q26, remember that many is just a synonym for some. So basically, how do you negate a some statement? You make it a universal quantifier in a conditional statement, or if it is a conditional statement, you take the first part, and negate the second part. I think this is tricky because it has a some statement WITH a conditional statement, and in negation we are used to the some statement not having the conditional statement.
Many farmers will not grow green manure unless they abandon the use of chemical fertilizers
This statement says some farmers will not grow green manure, unless they abandon the use of chemical fertilizers; so for some farmers, if they do not abandon the use of chemical fertilizers, they will not grow green manure.

For some farmers, this has growing green manure depending on abandoning chemical fertilizers. Or in other words, if they don't abandon chemical fertilizers (e.g. they use chemical fertilizers, they will not grow green manure). How do we find a world where this doesn't happen?

This is if all farmers use chemical fertilizers and grow green manure. That means it is impossible for some farmers to not grow green manure.

For PT77 S4 Q26: Sea Creatures have rarely if ever, wreaked ecological havoc in a new habitat unless they have been able to survive in that habitat after having been deposited by oceangoing ships.

So for this one, I would say, it is not the case that sea creatures have rarely if ever wreaked ecological havoc in a new habitat, unless they have been able to survive in that habitat after having been deposited by oceangoing ships.

So what does this mean?

/Rarely wreak ecological havoc in a new habitat ---> survive after being deposited by oceangoing ships.
keep /Rarely wreak ecological havoc in a new habitat
and
negate survive after being deposited by oceangoing ships.

*think of rarely, as few.

Some sea creatures don't rarely wreak ecological havoc in a new habitat (meaning it is common/most of the time that they the wreak havoc in the ecological habitat) even if they don't survive after being deposited by oceangoing ships.

OR, with the contrapositive we get the same thing:

/survive after being deposited by oceangoing ships. -->rarely wreak ecological havoc in a new habitat

/survive after being deposited by oceangoing ships.
and
negate rarely wreak ecological havoc in a new habitat

Some sea creatures that don't survive after having been deposited by oceangoing ships commonly wreak ecological havoc or do so most of the time.

kkole444

@"Merly Goodleaf" did a great explanation!
When I am negating necessary conditions I look too see if i can still conclude the argument with the new negation. if I cannot then I have the correct answer.
Also not that these are difficult questions.
PT73 S4 Q26
CXT–genetically modified crops that produce toxins to reduce incest pests do not need to be sprayed with insecticides.
Premise–since excessive spraying of insecticides on crops has harmed wildlife populations near wildlife.
Conclusion–using such genetically modified crops more widely is likely to help the wildlife recover.
A–Correct–
B–Incorrect—this makes another assumption on top of the one made in the argument. this is saying that if you lower insecticide levels, even by the smallest amount, wildlife is likely to recover. We have no idea if this is true. Maybe all insecticides have to be tossed out for the wildlife to recover. Plus if we lower insecticide use by say 1 small unit, do you think wildlife would recover? probably not. We need to assume that using less insecticide will cause less harm, we need to assume the new modified plants will cause less harm because the argument says that the new modified plants will likely help the wildlife recover.
C–Incorrect–we have no idea
D–incorrect–outside the scope we do not care about the cost, where is that mentioned?
E–incorrect–we do not have a conditional conclusion, skeptical of the conditional assumption, however, this is wrong because it is making more assumptions particularly how & why the new crops will cause less harm.

For instance A ' GMO crops as compared to insecticide spray is likely to cause less harm.
What if it will casue just as much harm or even more harm than insecticides? do you think then the wild life would recover like our conclusion wants? Nope--> correct AC
We are trying to conclude that the new modified plant will likely help the wildlife recover