Logical Reasoning

PT141 · S2 · Q20 The advent of chemical fertilizers

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The advent of chemical fertilizers led the farmers in a certain region to abandon the practice of periodically growing a "green-manure" crop, such as alfalfa, in a field to rejuvenate its soil.

Conclusion

To improve the soil structure, farmers will have to abandon chemical fertilizers.

Evidence

As chemical fertilizers came to the region, farmers stopped growing "green-manure" crops to rejuvenate the soil. As a result, the soil structure is now poor.

Evaluate

We're thinking, Did they tell us that chemical fertilizers ruin the soil structure?

No, not at all. The thing that killed the soil structure was when farmers stopped growing "green manure". Did they tell us that chemical fertilizers cause farmers to stop growing "green manure"?

Kinda. That did happen in the past: the advent of chemical fertilizers led them to abandon "green manure".

The author must be assuming that

If we look at this formally, the conclusion is saying Don't abandon -------------------> poor soil chem fertilizers structure

The evidence provided not growing -----> poor soil green-manure structure

So what the flow of logic is missing is that first piece, Don't abandon ---> not growing chem fertilizers green-manure

Goal

Look for an answer connecting , or an answer ruling out some way that we could improve soil structure while still using chemical fertilizers.

20.

The argument relies on the assumption that

  1. most, if not all, farmers

    Too Strong/Specific: most, alfalfa

    Whenever you're reading an argument and you see them pause to say "for example / such as", you know they'll put one of those examples in a trap answer. Examples aren't special or important. They just help the reader understand what we're talking about. But for LSAC, examples give them a way to set up the trap of "the only thing mentioned = the only thing". This author doesn't need to assume that any farmers start growing alfalfa. Any green-manure crop could rejuvenate the soil structure.

    11% picked this

  2. applying chemical fertilizers to green-manure

    Too Strong: no positive effect

    A potential objection to the argument could have been, "Hey, author, why do we need to abandon the chemical fertilizers? Can't we just bring back the green-manure crops and use both? Maybe the chemical fertilizers will even help the green-manure crops grow back more quickly." But this answer is such a strongly worded idea that the author hasn't committed herself to this. When we negate it, we don't get the storyline above, we get the weak idea that "chemical fertilizers has at least some positive effect on the growth rate of green-manure". The author could happily concede that putting chemical fertilizer onto green-manure crops could have a positive effect on their growth (maybe it speeds up the photosynthetic rate of the green-manure crop by 2%). That idea by itself isn't an objection. If we said "using chemical fertilizers and green-manure crops in tandem would not have a positive effect on soil structure", that would be a correct answer.

    5% picked this

  3. the most important factor influencing

    Too Strong: most important

    This is Necessary Assumption at its friendliest, giving us overly loaded language the author never committed to. Would the author's argument be changed or harmed if soil structure was the 2nd most important thing? No. The negation of really strong ideas rules out one extreme possibility, but it leaves room for tons of still-powerful possibilities.

    7% picked this

  4. chemical fertilizers themselves have a

    Out of Scope: CF's harm soil

    The author never committed herself to that idea, although it's easy to feel like she did since otherwise it's confusing why she's drawing such a harsh relationship between "can't improve soil w/o quitting chemical fertilizers". If someone were trying to improve their lung health by quitting cigarette smoking, but they had a compulsive habit of smoking any time they did a Sudoku out on the porch, you might conclude "to improve her lung health, she's gonna have to stop doing Sudoku's out on the porch". That doesn't mean you're assuming that "doing Sudoku on the porch itself has a destructive effect on the lungs". Our author is thinking that "as long as farmers have chemical fertilizers, they won't grow green-manure", so chemical fertilizers are indirectly leading to the degraded soil structure, but they're not the direct/proximate cause.

    34% picked this

  5. Correct

    many, if not all, farmers

    Why this is right

    When Necessary Assumption answers are conditional, we can diagram them and ask ourselves if the author seemed to be making that reasoning move. This one looks like this: Don't abandon Many, if not all, will not chemical fertilizers ? grow green-manure Our prephrase from before looks similar: Don't abandon ---> not growing chem fertilizers green-manure If we negated this answer, it would sound like "It's possible that farmers don't abandon chemical fertilizers, and yet many, if not all, farmers do grow green-manure crops". Would that be an objection? Yes. That allows us to argue that we could improve the soil, while still using chemical fertilizers.

    Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

    43% picked this

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