#20 - The advent of chemical fertilizers led the farmers in

[Brook Miscoski]

LSAT2018,

What I believe you to focus on for this question is quantity, not conditional reasoning. Remember that it can hurt you to try to force conditional reasoning onto a stimulus or answer choice when there is a better way of interpreting the information.

For these answer choices, (A) and (E) contain similar concepts:

(A) "Most, if not all," and,
(E) "Many, if not all."

These are both quantity concepts. "Most, if not all" means "more than half," and "many, if not all," means "at least many." The concept of "many" is less constraining than the concept of "most"--for example, 1 billion people is "many" by Earthly standards, but it is certainly not "most."

The only other answer choice that uses "most" is (C), and is discussing degree of importance rather than quantity.

If you try to interpret "many, if not all" (or the similar [A]), you get:

not All-->Many
not Many-->All

The contrapositive is nonsensical because how can you have All if you lack many? That tells you that the sufficient condition of the contrapositive is forbidden. You must have many, and you might have all.

It is way more work than necessary to break down the logic behind the expression--this is a quantity expression that you are probably familiar with, and it's okay to use your understanding of the common phrase. However, this is a good drill in case you come up against something you don't understand.

[dyogenes]

I'm struggling to see how E is a required assumption. It seems like it's very easy to negate E and have the conclusion still obtain. If we take the negation of E to mean:

"Farmers would grow green manure crops even when using chemical fertilizers"

It still may be necessary for farmers to abandon the use of chemical fertilizers if for instance the chemical fertilizers prevent soil rejuvenation from green manure crops grown by farmers who we grant will grow green manure crops while using chemical fertilizers. Or perhaps they harm it to degrees which GMCs can't mitigate.

If I can get to the conclusion without E, how is E an assumption the conclusion requires?

It's late enough in the day that I'm likely just be missing something very obvious.

Thank you!

[Adam Tyson]

Your negation of answer E looks really good, dyogenes, but your analysis of its impact is a bit off. Looks to me like you over-complicated things a bit. The negation of the correct answer does not need to disprove the conclusion - rather, it needs to ruin the logical structure of the argument. If that negation means that the premises no longer support the conclusion, the argument is destroyed, even if the conclusion might still possibly be true.

So, if farmer's can plant green manure crops without abandoning chemical fertilizers, is there any reason to believe, based on these premises, that they have to abandon chemical fertilizers? Or do the premises no longer support that conclusion? The fact that you had to spin out a whole "what if" scenario that went beyond what we were given in the stimulus suggests that the premises did not by themselves support the conclusion any more, and that means the argument, as given, is junk.

[dyogenes]

Thanks for the reply! But I'm still confused. Maybe this is where I'm going wrong. From what you're saying it sounds like when we talk about necessary assumptions, we're not talking about assumptions necessary for the argument's validity, but instead some other quality? Like, how much negating the assumption nullifies some amount of inductive weight?

Or in other words, the logical structure that the negated necessary assumption needs to destroy is some structure different than the validity of the argument? What is this other structure?

To me, necessary assumptions have always been claims without which validity is impossible - that was the structure they were necessary to preserve. Not only does E not guarantee validity, validity can be achieved without E.

Tangentially, in section 4 of this test (test 73) we see a question that (to me, on a first pass) seems relevantly similar. The key to finding the necessary assumption for #26 is recognizing that a new factor which rendered an old factor as fatally redundant may itself include harm to the system. Here, also, the correct answer A seems necessary for the argument's validity. But maybe this isn't a good analogue.

Are necessary assumptions necessary for validity or some other structure?

Thank you!

[Adam Tyson]

Again, I think you are confusing the validity of the argument (whether the premises support the conclusion) with the truth of the conclusion. A conclusion can be true even if the premises do not support it. For example:

"The lettuce in my refrigerator is rotten, therefore I will sleep late tomorrow."

What am I assuming? That rotten lettuce in my fridge somehow indicates that I will sleep late tomorrow. What if it does not? Then the argument is not valid, because the premise does not support the conclusion.

But I still might sleep late tomorrow.

The conclusion can be true even while the argument is logically, structurally, invalid. Necessary Assumptions are necessary for the validity of the argument, but may not be necessary for the truth of the conclusion. Don't mix up the validity of the argument - whether the premises support the conclusion - with the truth of the conclusion, which is independent of whether the premises support it or not.

[ShannonOh22]

I am also wondering about how the "many, if not all," quantifier affects the answer choice in a Nec Assump question...when negating, should we just remove that from the equation entirely?

The statement then becomes:

"Farmers in the region will grow green-manure crops only if they abandon the use of chemical fertilizers."

For some reason makes more sense to my brain, and E suddenly becomes a great answer choice. If it's an acceptable practice to disregard quantifiers in these situations, please let me know!

[Paul Marsh]

Hi Shannon! I agree that answer choice (E) jumps out a lot better once you look past the quantifier. However, ignoring quantifiers on the LSAT can be a costly mistake and I wouldn't recommend it as a rule in any circumstance. That said, "Many, if not all" is fairly wishy washy language. Unlike "most", "some", "all", "none", etc. - it doesn't really have a clear definition. That means that unlike those other terms, it doesn't have precise implications in formal logic. It's just there to suggest a large number - like in this answer choice for example it lets you know that a significant amount of farmers will not grow green-manure crops, and so you can feel confident that it's a good answer because of how many farmers we're talking about. "Many, if not all" translates more or less to "A bunch of", or maybe "A whole heck of a lot of" if you're a Midwesterner like me. So if you find yourself thrown off by the "Many if not all" phrase, I'd mentally replace it with something else. "A whole heck of a lot of farmers in the region will not grow green-manure crops unless they abandon the use of chemical fertilizers." Sounds like a good answer choice to me! Hope that helps.

[mrdmass725]

On a unrelated note is the sentence that begins with “as a result” the subsidiary conclusion because that sentence receives support and supports the main conclusion of the argument

[Adam Tyson]

It is, mrdmass725! Good eye!